Growing
Pests And Diseases Ravaging Your French Beans? Try These Control Options
IN THIS GUIDE 1) Slugs And Snails 2) Birds 3) Aphids 4) French Bean Rust 5) Halo Blight French beans, both climbing and dwarf, are widely grown here in the UK and usually without too many problems for the home gardener. However, there are some pests and diseases that can not only hinder, but destroy a potential crop of beans if swift action is not taken. The most common issues gardeners experience when growing French beans include: Slugs and snails Birds Aphids French bean rust Halo blight See our guidelines for dealing with each of these common problems below. 1) Slugs And Snails Slugs and snails can be a real issue for young French bean plants, especially during wet conditions, and can decimate a bed of seedlings overnight. Leaving behind their tell-tale slime tracks, slugs and snails feast on bean foliage and can cause irreparable damage. There are several control options available to protect against these French bean pests, but a combination of several can often prove most effective, along with only planting out strong robust plants. Barrier controls essentially place a substance around the bean plant which these troublesome gastropods don’t like to climb over. From copper tape to crushed eggshells and gravel, they are easily available and include sustainable options. “From personal experience and many studies conducted, it has been discovered barriers of copper tape, crushed eggshells and gravel are ineffective in controlling gastropod (slug and snail damage). “I use a layer of petroleum jelly around the base of my plants and remove the bottom few leaves to control slugs and snails on my beans.” Encouraging slug and snail predators such as frogs, toads and hedgehogs into the garden can also be beneficial as they will reduce their numbers by eating them. Removing slugs and snails by hand at night under torchlight can be surprisingly effective as well, as vast numbers can quickly be collected. 2) Birds Some birds can be a real problem when growing French beans, especially the common pigeon, which eats the leaves and soft growing tips of bean plants. The only effective way of preventing bird damage is to net the plants, especially when the beans are young or when growing dwarf varieties. The netting does need to be supported by hoops or canes though, as they will even land on the netting to get at the foliage underneath. 3) Aphids Black bean aphids or blackflies are only small at up to 2mm in length and can be tolerated in small numbers, but larger infestations can cause stunted growth and poor harvests. Commonly found on the growing tips and underside of the leaves, the aphids leave behind a sticky honeydew that often attracts ants. If low levels of aphids start to increase, control measures can include squishing by hand, spraying them off with a hose gun attachment and encouraging aphid predators into the area, such as ladybirds and hoverflies. “Some aphids on my bean plants don’t particularly bother me, as the plant can normally handle them, but if you want to help prevent some colonisation of aphids, you can pinch off the tips of new growth as the plant comes into flower,” advises Master Horticulturist Dan Ori. “This removes the most attractive food source for the aphids.” 4) French Bean Rust Rust is a fungal disease spread by spores that can affect both runner and French beans, resulting in poor growth and leaf drop. Often encouraged by wet conditions, rust begins as pale spots develop on the tops of the leaves before covering both sides in tiny black pustules – finally leading to the leaves dying and falling from the plant. Rust, thankfully, tends to affect beans later on in the season, which hardly affects the bean crop. However, if rust is spotted early on in the summer it is advisable to remove any affected foliage and destroy it, rather than adding it to a home compost system, to prevent contagion. As a fungal disease, it is important not to save and store any seed from French bean plants affected by rust to prevent any future issues. 5) Halo Blight Halo blight, aptly named due to the yellow halo that forms around small brown blotches that appear on the foliage, is a bacterial disease that can affect French bean varieties. Transmitted by seed, if halo blight is confirmed or even if suspected, then no beans should be saved to sow from the affected plant. If halo blight appears on a few plant leaves it is recommended to try removing only the affected leaves. “Halo blight is one very good reason to use annual crop rotation when growing vegetables, and I recommend not saving seed but starting again, with fresh shop-bought seed the next year,” adds Dan. However, if the plant is badly affected, then its entire removal and disposal are advisable, along with avoiding growing beans in the same location for several years.
Learn more
Identifying Blue Mint Beetle: Are They A Problem And Do They Need Removing?
IN THIS GUIDE What Is The Blue Mint Beetle? Identification What Else Might Be Eating Mint Leaves? Is Blue Mint Beetle A Problem In The Garden? Removing Blue Mint Beetle References According to the RHS, the blue mint beetle was first found breeding in the UK in 2011 – but is this what is eating your mint, and if so, what should you do?1 These blue beetles are widespread in mainland Europe and have been spotted in several locations in South and East England and in parts of Southern Scotland.2 They might spread elsewhere in the British Isles as our climate continues to alter. “The Blue Mint Beetle is widely distributed in mainland Europe and, as with other plants and animals, its range is spreading northwards as the global climate heats, including into the UK,” says RHS Master of Horticulture Colin Skelly.3 Spotting a glimmering dark blue beetle in your mint is honestly more likely to be interesting than alarming. Though a pest, its threat to your plants is only minor. What Is The Blue Mint Beetle? The blue mint beetle is scientifically known as Chrysolina coerulans. It is a species often found in damp meadows and riverside habitats. Chrysolina coerulans are related to the British native Chrysolina herbacea, the green mint beetle. As larvae and as adults, they feed on the foliage of Mentha species. The green mint beetle is rarely an issue for gardeners as it more commonly feeds on wild mint species. Identification While the blue and green mint beetles are related, the two cannot usually be confused as adults. As the common names suggest, the blue mint beetle has a dark blue hue, while the native green mint beetle is emerald green. Adult blue mint beetles are 7mm long.4 Blue mint beetle larvae grow to around 1cm in length and they have black, soft, rotund bodies. At this stage in their lifecycle, they are very similar to the larvae of the native green mint beetle. What Else Might Be Eating Mint Leaves? Mint is also eaten by several other pest species. As well as providing food for green and blue mint beetles, mint leaves are also eaten by the caterpillars of several moth species in the Pyrausta genus. You may see their silk threads loosely twined around the shoot tips and upper leaves. Slugs and snails also can be found on mint leaves, though this is not usually a problem. Is Blue Mint Beetle A Problem In The Garden? Blue mint beetle is not really a problem in the garden. While these and the green mint beetles will eat mint, mint is such a prolific and vigorous plant that their feeding will not usually pose any threat to the plants. This species will probably not be able to fully decimate a mint crop, so their presence can usually be tolerated. Both the larvae and the adult will feed on mints and tansies in the spring and summer months, creating small irregular holes in the leaves, but these will not be a major problem in most instances and there should still be plenty of mint for you to harvest if you have a reasonably well-established clump. Mint is usually one of the more trouble-free plants in a garden. In fact, in certain settings, it can become too successful, crowding out and out-competing other herbs or other plants grown close by. Where mint is used as a ground cover plant – in a forest garden for example – its tendency to spread quickly and easily can be an advantage. In such settings, you will likely be unconcerned about a beetle taking some nibbles here and there. Where mint is grown in a garden bed or dedicated herb garden, it is often kept in check by placing it within a pot sunken in the ground. Of course, you might also simply grow some mint in its own pot in a container garden. In such settings, you may wish to remove pests like blue mint beetles which settle on your smaller plants. Removing Blue Mint Beetle It is usually perfectly possible to find and remove both the larvae and the adults by hand. If you would rather not kill these beetles, then you might instead consider tolerating their presence and perhaps planting more mints to act as trap crops so you do not lose too much of your harvest. Remember, blue beetles, like other beetles, are food for garden wildlife and though they are relative newcomers to our shores, their presence is not considered to be much of a problem. References 1. Blue mint beetle. (n.d.). Royal Horticultural Society. Retrieved March 9, 2023, from https://www.rhs.org.uk/biodiversity/blue-mint-beetle 2. Mint Leaf Beetle. (n.d.). Nature Spot. Retrieved March 9, 2023, from https://www.naturespot.org.uk/species/mint-leaf-beetle 3. Salisbury, A., Halstead, A. J., & Malumphy, C. (2012, January 1). First record of blue mint beetle Chrysolina coerulans (Scriba, 1791) (Chrysomelidae) breeding in Britain. ResearchGate. https://www.researchgate.net/publication/280921405_First_record_of_blue_mint_beetle_Chrysolina_coerulans_Scriba_1791_Chrysomelidae_breeding_in_Britain 4. Blue mint beetle. (n.d.-b). Project Noah. Retrieved March 9, 2023, from https://www.projectnoah.org/spottings/673486003
Learn more
Lime Can Be Used To Reduce Soil Acidity, But How And When Should It Be Used?
IN THIS GUIDE What Is Garden Lime? Why Is It Used? Should You Use Lime To Amend Acidic Soil? Do You Need To Use Lime In Your Garden? Alternatives To Garden Lime Determining Quantities For Liming Applying Materials To Reduce Soil Acidity References Lime is commonly used to reduce soil acidity, but how and when should it be used? Conventional horticultural practice involves using lime to raise the pH of acidic soil. However, sustainable gardeners are increasingly aware of the environmental costs of the extractive industry and since lime comes from limestone quarries, which can cause significant environmental harm, some gardeners are now seeking more sustainable, renewable alternatives.1 Sustainability practices in the extraction of garden lime certainly vary widely from site to site, but while practices have often improved, these are still part of an extractive rather than regenerative mindset. Garden lime is a natural material which is suitable for organic production, but just because it is a natural substance, that does not mean that it is necessarily the most eco-friendly option, so this is certainly something to consider before you choose to use lime in your garden. What Is Garden Lime? Garden lime is a calcium carbonate-rich material made by grinding limestone. There is also a variant called magnesian limestone, also known as ‘Dolomite lime’ which is rich in magnesium carbonate as well as calcium carbonate and is used in lime soils which also lack magnesium.2 Some gardeners may also use hydrated lime (calcium hydroxide) which is commonly used in construction.3 This has a higher neutralising value and so less of this can be used to have the same affect on the soil. Why Is It Used? Lime is used to reduce the acidity of garden soil by increasing the pH level. Garden soil is either acidic, neutral or alkaline. Soil that is very acidic can cause issues as it can be more difficult for plants to derive the nutrients they need from strongly acidic soil, and there can also be a toxic build-up of aluminium and other substances in extremely acidic situations.4 Raising soil pH can also help to avoid certain plant diseases, such as clubroot of brassica crops.5 Should You Use Lime To Amend Acidic Soil? Reducing acidity can be required in situations where the soil is particularly acidic to avoid nutrient deficiencies and other issues with plants. However, sometimes gardeners may simply make the choice to reduce a somewhat acidic soil in order to grow plants which like more neutral or alkaline conditions. In my opinion, it is usually best, in all but the most extreme of conditions, to work with and plant for the soil that you have in an organic garden. There are plenty of plants which will thrive in moderately acidic soil. Ericaceous plants love acidic conditions, and a number of further plants can tolerate them as long as they are not too extreme. Broad and larger scale liming in gardens is not often required. If lime is used, it is simply used in a particular growing area to improve conditions for certain crops, while the majority of the garden is given over to plants which thrive in the natural conditions. Do You Need To Use Lime In Your Garden? The first and most important step in deciding whether to use lime is to determine the pH of the soil in your garden. For this, you will need a pH testing kit, which is readily available online and not very expensive. It is always a good idea to check pH before planting new trees or shrubs, or establishing a new kitchen garden. It is important to note that the degree of acidity is important when deciding whether to lime to reduce acidity. A very slightly acidic soil, with a pH of 6.5, is actually considered to be the best possible pH level for the growth of the vast majority of garden plants.6 With a pH of 6, some liming may be beneficial, but it is only when the pH falls below 5.5 that more severe issues can crop up, and reducing pH is more likely to be required. Once you know your pH, and have decided whether you need to reduce acidity, you should think about which material you wish to use. While garden lime, Dolomite lime or hydrated lime, are the most common options, sustainable gardeners may be interested in other, more eco-friendly options. Alternatives To Garden Lime If you need to reduce acidity in garden soil, one other option is calcified seaweed. Calcified seaweed is produced from naturally occurring calcified and coral-like algae which are naturally occurring.7 However, even more than limestone quarries, there are serious sustainability concerns over the process of obtaining this product, which damages marine environments.8 Another very interesting alternative is ground eggshells, which studies have suggested could be just as effective as lime when applied as a ground powder in an agricultural setting. On a small scale, certainly, in gardens, using powdered crushed eggshells to reduce soil acidity could certainly be an interesting and more eco-friendly alternative. “Although I would love to use eggshells instead of quarried lime, the scale and grinding process deployed in agricultural trails cannot currently be practically replicated in the domestic garden,” shares Master Hortocilturist Dan Ori. Determining Quantities For Liming Of course, lime, while not ideal from a sustainability standpoint, is readily available, and it will be far easier to determine exactly how much of it will be required in order to reduce the soil pH to the optimal level of 6.5. So, if you have more extremely acidic soil, and do not want to experiment with finely ground eggshells, then it is likely that you will still want to use it. The quantities that you will need to apply over a given area will vary depending on: The type of liming material you choose The type of soil in your garden (soils with high clay content will be more resistant to pH change and so more liming material will be required) The soil pH (and how much of a reduction in acidity is required) To raise the pH of clay soil, typically you will require around 1kg per square metre (m2) of garden lime to raise the pH from 5.5 to 6.5. This falls to around 0.8kg / m2 in loam soil and to around 0.7 kg / m2 in sandy soil. Obviously, more will be required if you need to raise it from a lower pH, and less if the current pH is higher. The quantities required will be different if you use Dolomite lime or hydrated lime. Applying Materials To Reduce Soil Acidity Liming must be carried out several months before planting in order for the necessary change in soil pH to occur. It is usually carried out for vegetable plots in autumn so that the soil pH should have altered by the time that beds are planted up in spring. Typically, it is said to be best to dig half of the lime into the soil and sprinkle the rest on the surface. However, in a no-dig garden, soil is not dug and is left as undisturbed as possible, so sprinkling the lime on the surface or incorporating it in the lower layers of a new lasagna garden may be best. If in doubt about what is required for your garden, it is not a good idea to try to change soil pH drastically without further investigation, since getting it wrong can do more harm than good. References 1. Quarrying and the environment. (n.d.). British Geological Survey. Retrieved March 20, 2023, from https://www2.bgs.ac.uk/mendips/aggregates/environment/intro.html 2. Young, B. (n.d.). Magnesian Limestone, South Shields. The Geological Society of London. Retrieved March 20, 2023, from https://www.geolsoc.org.uk/GeositesMagnesianLimestone 3. Lime and liming. (n.d.). Royal Horticultural Society. Retrieved March 20, 2023, from https://www.rhs.org.uk/soil-composts-mulches/lime-liming 4. Soil acidity. (2020, December 29). Agriculture Victoria. Retrieved March 20, 2023, from https://agriculture.vic.gov.au/farm-management/soil/soil-acidity 5. Club root. (n.d.). Royal Horticultural Society. Retrieved March 20, 2023, from https://www.rhs.org.uk/disease/club-root 6. Best pH levels and how it effects plant growth. (n.d.). Canna UK. Retrieved March 20, 2023, from https://www.canna-uk.com/ph_acidity 7. Seaweed products. (n.d.). Royal Horticultural Society. Retrieved March 20, 2023, from https://www.rhs.org.uk/soil-composts-mulches/seaweed-products 8. Campbell, I., Macleod, A., Sahlmann, C., Neves, L., Funderud, J., Øverland, M., Hughes, A., & Stanley, M. (2019, March 22). The Environmental Risks Associated With the Development of Seaweed Farming in Europe – Prioritizing Key Knowledge Gaps. Frontier. Retrieved March 20, 2023, from https://www.frontiersin.org/articles/10.3389/fmars.2019.00107/full
Learn more
Daffodil Blindness: Specialist Growers Share Common Reasons Narcissus Doesn't Flower
IN THIS GUIDE What Is Daffodil Blindness? Why Do Daffodils Come Up Blind? Reducing Chances Of Daffodil Blindness References Daffodil blindness can be a disappointing problem and you might not know how to fix the problem. In this article, we’ll take a look at this issue and what you might be able to do about it. What Is Daffodil Blindness? Daffodil blindness is the name given to the phenomenon when daffodils come up with foliage but do not flower. The leaves can be healthy and numerous, yet flowers do not form. “Daffodils that grow but fail to bloom because of daffodil blindness might not bloom because of several causes,” says Janet Hickman from the American Daffodil Society. “Some, especially those with late-season double flowers, may ‘blast’, meaning the bud appears but dries up and fails to open, usually due to the weather becoming too hot too soon.” It can be caused by environmental conditions, gardener error, or several different pests or diseases. In general terms, daffodil blindness is a sign that the development of the bulbs has been affected in some way. Why Do Daffodils Come Up Blind? Environmental Conditions After they have flowered and the flowers have faded, daffodils should continue to grow for a further period of a few weeks, to replenish their energy stocks through photosynthesis. This energy is stored in the bulb for next year. In certain environmental conditions, such as when there is a drought or the weather is very dry, daffodils may die prematurely, before these energy reserves have been stored. “A prolonged period of dry weather after flowering was the most common reason for daffodil blindness this year as it followed the early drought last year (2022),” shares Master Horticulturist Colin Skelly. “Usually mowing too early is the culprit.” “A planting site that was once ideal may gradually become overshadowed by the growth of trees and shrubs causing a decline of daffodil flowering,” explains Janet. Anne Wright from Dryad Nursery recommends moving your plants to a sunny location if they are growing in the shade or cutting back any overhanging branches from nearby trees and shrubs that may be blocking the light from getting to your plant. Blindness can also occur due to a lack of nutrition in the growing medium or soil. Daffodils that have just been planted the previous year will usually flower well in their first year, but in poor and low-nutrient soil, performance can diminish rapidly and blindness can occur. If you have had successful daffodil blooms over a number of years, in a bed or border, or in pots, the blindness may have occurred due to overcrowding.1 Overcrowding can lead to blindness or poor flowering. Gardener Error A number of errors by gardeners can also be to blame for daffodil blindness. One issue may be that bulbs were planted too late as bulbs planted after September will not tend to do as well. The bulbs may also have been planted too shallowly in the soil. Planting daffodils too shallowly can encourage the formation of lots of small bulbs – too small to flower successfully. Another big mistake that gardeners can make which can lead to blindness is removing or mowing over daffodil foliage too soon after flowering. As mentioned above, daffodils require a period of active growth after flowers fade in order to gather up energy reserves for the following year. Gardeners may also, in the pursuit of a neat and tidy garden, knot up the foliage after flowers fade, tying them together in a bunch. This can also cause problems as the leaves will not be as able to gather the energy they need for successful flowering the following year and blindness can occur. Pests & Diseases Pests such as narcissus eelworm and narcissus bulb fly can damage bulbs below the soil, which can lead to poor flowering or blindness. “Bulb flies can attack the growing bulb, depositing eggs that hatch into destructive larvae,” says Janet. If daffodils do not flower, this can also be due to diseases like daffodil viruses and narcissus basal rot.2 These things can sometimes cause bulbs to die altogether, but can also simply lead to a decline in flowering. Usually, if a pest or disease is to blame, the issues can be hard to detect, but foliage may appear stunted or yellow prematurely. Reducing Chances Of Daffodil Blindness Many of the causes of daffodil blindness can be removed through careful preparation and plant care. Environmental conditions and causes related to gardener error can often be remedied relatively easily by the gardener. 1) Improve Environmental Conditions Preparing the site well before planting can help reduce the chances of blindness. The American Daffodil Society recommend growing your daffodils in a position that receives at least 6 hours of sunlight a day in soil that is very well-draining. Make sure that any issues with compaction and poor drainage, or excessively free-draining soils have been addressed. Add plenty of organic matter. Make sure you have chosen a suitable spot for your daffodils which will not become too dry. When dry conditions prevail after flowering, water thoroughly and well until the plants show signs of dying down naturally. Mulching around your bulbs with organic matter will help reduce moisture loss and will also help by adding slow-release nutrients to the soil. Where flowering declines rapidly and nutritional issues are suspected, consider feeding daffodils with a general-purpose organic fertiliser in the spring. Anne Wright suggests feeding your plants with a high-potash fertiliser at the first sign of something being not quite right. After flowering, especially when daffodils are grown in containers, it can also be helpful to feed every couple of weeks with a high-potassium organic liquid plant feed, from when the blooms have faded until the plants begin to die back naturally. If your daffodils are blind due to overcrowding, lift the bulbs when the foliage dies back. Replant bulbs in a bed or border so that there is a gap of at least 5-7.5cm between each one, making sure that you add plenty of organic matter such as homemade compost or well-rotted manure before replanting. 2) Plant Quality Bulbs At The Correct Depth First of all, make sure that you start out with good quality daffodil bulbs so that you can expect to achieve the best results when you get things right. If you want to naturalise daffodils in a lawn area, then make sure you select bulbs which are well suited to this situation. Ideally, plant these bulbs before the end of September, and wherever they are to grow, plant the bulbs at 2-3 times their own depth. Make sure that you leave daffodil foliage in place for a period of at least 6 weeks to allow them to build up energy reserves for next year. “Don’t cut back or tie the leaves after flowering, and watch for slug damage on flowers,” Anne warns. Allow them to remain and photosynthesise naturally. 3) Address Any Pests Or Diseases Unfortunately, there is no treatment for narcissus bulb fly or typical daffodil diseases. If you suspect that pests or disease are the issue, any affected bulbs should be removed and destroyed. If you have unearthed daffodil bulbs to find larvae of the narcissus bulb fly, get rid of infested bulbs and consider covering any remaining plantings with insect-proof netting between mid-May and early July, which may discourage the females from laying their eggs. Remove any bulbs suspected to be diseased as soon as possible. If basal rot has occurred, but you wish to continue to grow narcissus in a given location, consider opting for N. tazetta cultivars, which are resistant.3 If you bear all the above in mind, you should often be able to avoid this issue and be able to solve the problem of blind daffodils or poor daffodil flowering in your garden where it has occurred. References 1. Daffodils won’t bloom if too crowded. (2016, January 7). Livingston Daily Press. Retrieved March 14, 2023, from https://eu.livingstondaily.com/story/life/home-garden/2016/01/07/daffodils-bloom-crowded/78135090/ 2. Narcissus basal rot. (n.d.). Royal Horticultural Society. Retrieved March 14, 2023, from https://www.rhs.org.uk/disease/narcissus-basal-rot 3. Narcissus tazetta “Geranium.” (n.d.). Royal Horticultural Society. Retrieved March 14, 2023, from https://www.rhs.org.uk/plants/224368/narcissus-tazetta-geranium/details
Learn more
You Can Prevent Broccoli Plants From Bolting By Following These 7 Important Rules
IN THIS GUIDE 1) Choose The Right Location 2) Sow & Plant At The Right Time 3) Practice Companion Planting & Crop Rotation 4) Mulch Plants To Keep Soil Cool 5) Water Broccoli Plants Correctly 6) Harvest Promptly 7) Choose Bolt-Resistant Varieties References Broccoli is still edible once it has bolted, but it can be disappointing if it occurs early and you have not obtained a worthwhile yield from your crop. Broccoli plants can be prone to bolting (running prematurely to flower and set seed) when the environmental conditions are not right. Most commonly, broccoli and Calabrese will be most likely to bolt due to stress caused by temperatures (most commonly too high but also potentially too low early in the growing season), water shortage, or a lack of nutrition.1 Sometimes, extreme weather conditions may be to blame for the bolting – and environmental factors may be largely out of your control. However, a lot of the time, the decisions you make and what you do as a gardener can be to blame. Once a plant has bolted, you can slow it down, but unfortunately can’t bring it back. However, taking steps to prevent your crops from bolting in the first place can often help you avoid disappointment – and making changes can help you grow broccoli more successfully in future if this is a problem that you have encountered more than once in your garden. So, to reduce the chances of bolting broccoli plants, here are a few tips: 1) Choose The Right Location Choosing the right spot for growing broccoli can help you avoid many of the common issues – bolting included. Remember that bolting is caused by stress of some kind, which encourages the plants to rush to reproduce. Plants that are placed in a suitable location with good, fertile soil (or growing medium) and optimal conditions in terms of sunlight and temperatures are far less likely to have a problem. Broccoli likes a situation in full sun or very light shade, with a fertile, and moisture retentive yet well-drained soil. In very hot summers – especially in the south – a lightly shaded spot may be preferable, since broccoli forms better heads in cooler summers here in the UK. In a very hot location, when temperatures rise too high, broccoli is far more likely to bolt. 2) Sow & Plant At The Right Time When exactly you sow your broccoli will depend on which type and variety you are growing and where you are growing it. Typically, seeds can be sown between March and June or July. Seeds are sown indoors or under cover in seed trays or pots before the last frost date, and can be direct sown, usually, from some time in April onwards. Sowing earlier can sometimes be a good policy for summer-harvested heading broccoli (Calabrese) since you can harvest before the weather heats up too much. However, sowing too early can sometimes be problematic too, since plants can bolt if they are not potted up or planted out in time and the roots become too confined or starved of nutrients in their containers. If indoors grown plants are placed outside too early, or placed out without hardening off, they may be stressed and may bolt due to a cold snap or too extreme a change in temperatures and conditions. So make sure you are aware of the temperature expectations where you live, and keep an eye on weather forecasts before you decide to plant your broccoli outdoors. 3) Practice Companion Planting & Crop Rotation Generally, the healthier and happier your broccoli plants are, the less likely they are to experience the stress that can lead to bolting. Like us, broccoli plants will be happiest when they have good neighbours. So make sure you think about companion planting, which can improve environmental conditions, reduce pest problems, and help maintain a balanced and fertile growing area. Practising crop rotation with brassicas like broccoli can also help make sure that the soil remains healthy and the plants are less likely to succumb to diseases or be stressed in other ways which cause them to bolt. 4) Mulch Plants To Keep Soil Cool Another important strategy to maintain the fertility of your growing areas and meet broccoli’s higher nitrogen needs is to mulch well around your plants with a nitrogen-rich organic mulch material. A mulch won’t only help maintain fertility and a healthy soil, it will also help reduce competition for the broccoli from weeds that might pop up. Crucially, it can also help keep the soil cool. Broccoli does not typically bolt due to high air temperatures, but rather due to high temperatures of the soil. Keeping the soil cool with an insulating blanket of mulch will help stop roots from overheating during warm summer weather. A good mulch should also help keep conditions moist, and reduce the amount of water that is lost through evaporation from the soil surface around your broccoli plants. This should help reduce issues caused by drought, which can be another common cause of bolting. 5) Water Broccoli Plants Correctly Of course, in addition to taking steps to conserve water in the soil, it is also important to make sure that you water your plants sufficiently, especially during the summer months. Broccoli is quite a thirsty plant. Typically, you will need to water outdoors grown plants every 10-14 days in dry weather – more frequently of course if you are growing broccoli under cover, or in containers. When watering, make sure that you water plants at the base, rather than from above, to use water more efficiently and make sure that it gets where it needs to go – into the soil around plant roots. If you have a larger garden, or struggle to maintain your watering routine, consider adding drip irrigation, and perhaps an automated system, to make things easier. 6) Harvest Promptly While plants will sometimes bolt prematurely, it is also important to remember that broccoli can also begin to flower and go to seed if you simply leave it too long before you harvest your crop. Keep on top of harvesting and harvest promptly to make sure you make the most of your produce and do not miss out. 7) Choose Bolt-Resistant Varieties Finally, if you consistently experience problems with broccoli bolting in spite of your best efforts, you might like to consider trying to grow more bolt-resistant varieties next year. Some broccoli cultivars are less prone to bolting than others. Hybrid F1 seeds often have better resistance to bolting and handle stress better, though you should note that these will not come true from seed like heritage varieties. References 1. Bolting in vegetables. (n.d.). Royal Horticultural Society. Retrieved March 13, 2023, from https://www.rhs.org.uk/vegetables/bolting
Learn more
Defoliation: What To Do If Your Plant Suddenly Starts Losing A Lot Of Leaves
IN THIS GUIDE What Is It? The Causes What Happens After Identifying The Cause Finding A Solution References A tree or other plant suddenly and unexpectedly losing a lot of leaves can be shocking. Identifying the cause of defoliation can be challenging, but this article may help. In this article, we will introduce you to defoliation and its common causes, help you to identify the cause of the problem, and give you some tips that might help you save your plant – or, at the very least, reduce the chances of you having the same issue again in future. What Is It? Defoliation is the name given to plants losing all, or a large proportion of their leaves. This is sometimes also known as leaf loss, or leaf abscission. Leaf loss can be due to natural plant processes, stress factors which cause the plants to drop leaves as a form of plant defence, or external factors. If a tree, shrub or other plants in your garden suddenly becomes defoliated, you’ll need to play detective to try to determine the cause of the issue. The Causes First of all, remember that some plants will naturally lose their leaves as winter approaches. Deciduous plants lose their leaves in autumn, enter a period of dormancy over the coldest part of the year, then burst into new growth in the spring. So make sure that this defoliation is not simply a natural part of the lifecycle of the plant. If defoliation has occurred on plants that would not usually lose their leaves, or has occurred at a different time of year, there are a wide range of different things that could be to blame. Common causes include: Environmental issues (to do with temperatures or water). Grazing animals. Insect infestation. Diseases (fungal or bacterial). Fertiliser or herbicide contamination What Happens After A plant that loses some but not all of its leaves may eventually recover, though its growth will likely be stunted. However, in many cases with non-life cycle defoliation, if all the leaves are lost, the plant is unlikely to be able to make a comeback and unfortunately, will often die.1 Most plants need leaves to survive. The leaves are the ‘factories’ where photosynthesis occurs, where they use sunlight and carbon dioxide to create the energy reserves they need.2 Whether or not a plant can survive defoliation will depend on how many leaves have been lost, the type of plant, and when exactly the defoliation has occurred. Evergreen plants store a substantial part of their energy reserves in their leaves, so defoliation can often kill them because they not only lose their ‘factories’ but also their starch reserves.3 Deciduous plants, on the other hand, store reserves elsewhere, in stems, trunks and roots, so they can often withstand defoliation more easily. Deciduous trees and shrubs can tolerate the loss of up to half their leaves and will often survive. Even those which lose more than half of their leaves may make it through. However, if the defoliation occurs over multiple years, the trees will be weakened and will not survive further leaf loss. Sometimes, when defoliation happens on deciduous plants earlier in the growing season, plants have time to put out a second flush of growth to replenish energy supplies before winter. In the middle of the season, deciduous plants may not have time to recover. If defoliation has occurred not long before natural leaf drop, this may not be as much of an issue. Identifying The Cause The first thing to determine is whether environmental issues have led to defoliation. 1) Temperatures Extremely high and unexpectedly low temperatures can both cause this problem. So think about the temperatures that a given plant can be expected to survive, and look at whether the temperatures in your area have jumped outside of that range. 2) Water When it comes to environmental issues, water is another important thing to look at. Has there been extremely high rainfall, or a period of drought? Might you have watered your plant too much or too little? Too much water and too little can both cause defoliation in their own right – but note that they can also increase the likelihood of defoliation due to disease. Often, it can be difficult to determine whether water issues of disease are the actual cause of the defoliation – but in either case, the issue can often be traced back to water. If you have ruled out an environmental issue with temperature or water, think about whether the leaves fell off, or were eaten! 3) Pests Deer and rabbits can quickly eat a large number of leaves, and may make you think that these leaves simply dropped off if you do not catch them in the act. If you look out, you may well be able to see the foragers to blame in your area, and identify how and where they entered your garden. Leaves may also have been eaten by a wide range of insect pests, such as sawflies, grubs, caterpillars etc. There are a huge, huge range of pests that can quickly eat a lot of leaves, defoliating your plants. Narrowing down the list of potential culprits will involve, first of all, looking at the list of common pests for a particular plant species. The culprits themselves may still be around if you look closely at your plants. 4) Plant Diseases Unfortunately, trying to work out which particular disease plants may have is not always easy. Again, you can narrow down the likely diseases by looking at the most common issues for a particular plant. Finding A Solution If sudden temperature changes or weather extremes were to blame then unfortunately there is not likely to be much that you can do, other than simply waiting to see if your plant will recover. Mulch well around the base of your plant with organic matter to provide slow-release fertility to give it the best possible chance. If too much water was the problem, or waterlogged conditions have arisen, taking steps to improve drainage through adding organic matter or even moving the plant to a free-draining location could help improve the chances of recovery. If there has been a drought, obviously providing water will be a top priority. Look at changing the location of plants or improving the soil if you are seeing repeated issues of these sorts. If leaves have been eaten by deer or rabbits or other foraging creatures, take steps to protect your plants. Make boundary hedgerows or protective rings with plants which provide them with food, or which they will not eat, to distract them or encourage them to browse elsewhere, for example. You could even use physical barriers or tree guards where necessary. Insect pest numbers can be kept down in a number of ways in an organic garden. Pick off pests you do find on your plant by hand and take steps to apply integrated pest management in your garden. This means attracting wildlife for natural predation, boosting biodiversity and taking other steps to maintain balance in the ecosystem in an organic way. Some diseases can be managed with organic control, and mitigated with garden hygiene practices (like removing all infected leaves from the plants and from the ground). Others unfortunately are much more challenging to manage – treatment will very much depend on the specific species, and on the plant and disease in question. References 1. Atkinson, R. R. L., Burrell, M., Rose, K. E., Osborne, C. P., & Rees, M. J. (2014). The dynamics of recovery and growth: how defoliation affects stored resources. Proceedings of the Royal Society, 281(1783), 20133355. https://doi.org/10.1098/rspb.2013.3355 2. Photosynthesis. (n.d.). National Geographic. Retrieved March 14, 2023, from https://education.nationalgeographic.org/resource/photosynthesis/ 3. Leaves. (n.d.). Young People’s Trust for the Environment. Retrieved March 14, 2023, from https://ypte.org.uk/factsheets/leaves/why-do-some-trees-stay-green
Learn more
10 Plants Mosquitos HATE According To Horticulture Specialist Gary Bachman
IN THIS GUIDE 1) Basil 2) Bergamot 3) Catnip 4) Citronella 5) Eucalyptus 6) Lavender 7) Lemongrass 8) Marigolds 9) Mint 10) Rosemary References Keep those pesky insects at bay with these mosquito-repellent plants. Perhaps the most notorious of all members of the insect kingdom, in the UK, there are 34 known species, and though they don’t carry the same maladies as in other parts of the globe, they can certainly be quite the nuisance. Indeed, their pesky presence during the summertime can turn basking in the sun from an indulgence into an ordeal for many British homeowners. According to research by MSU Horticulture specialist Gary Bachman and various authors at the USA National Institute of Health, some of the best plants to help to repel mosquitos include: Basil Bergamot Catnip Citronella Eucalyptus Lavender Lemongrass Marigolds Mint Rosemary Learn more about the effectiveness (and how to grow) each of these below. And remember that although the following plants aren’t 100% guaranteed to ward off mosquitos from your back garden, they certainly help to create a more hostile environment for these unwanted guests. 1) Basil As good for pasta as it is for pests One of the most popular herbs in the UK, basil is famous as a flavour enhancer for a range of culinary dishes, though it’s perhaps most closely associated with Italian cuisine. But did you know it’s also effective as a mosquito repellent? For best results, place a few basil plants throughout your house – preferably near doors and windows to deter mosquitos from entering the premises in the first place. They can survive outside, though they don’t tolerate frost and dislike waterlogged soil. 2) Bergamot Good for bees, bad for mosquitos Variously known as bergamot, wild bergamot, horsemint, monarda and bee balm, this colourful flower is also adept at discouraging the presence of unwanted insects in your back garden. As well as adding a splash of vibrancy to your outdoor display, bergamot will also attract butterflies and bees by the shedload. 3) Catnip More effective than DEET? While humans might be the preferred food source of mosquitos, they’re generally not that fussy. This means cats are at just as much risk of being bitten as we are. Thankfully, the same chemical (nepetalactone) in catnip which drives cats to distraction can help to keep them safe from the unwanted attention of mosquitos. It’s a good idea to plant several plants around your garden to keep the pests away. Just be mindful that the scent of catnip can turn cats into crazed maniacs, so be sure to plant them in areas that won’t overly attract felines. 4) Citronella The potent fragrance of citronella overpowers mosquitos Citronella is perhaps the plant on this list that is most used in commercial insect repellent products. As well as its extract being imbued in sprays and creams, it’s also widely used in candles to deter all sorts of winged interlopers. That’s because the strong lemon fragrance which the plant exudes is enough to overpower the sensitive senses of mosquitos and other insects. Since they rely on their sense of smell to detect the carbon dioxide (and sweat!) that humans emit, citronella can effectively mask our presence from them.1 Therefore, citronella is a strong choice for any garden environment which is plagued by bugs of all types. It can grow to a decent size but still does admirably well in pots, which may be sensible since it doesn’t do well with frosts. 5) Eucalyptus A mosquito repelling tree! A native of Australia, eucalyptus is perhaps most famous as the favoured foodstuff of koala bears. However, its oils also have a range of other benefits, including discouraging mosquitos, midges and ticks from setting up shop in your back garden. Be aware that eucalyptus trees can grow to almost 30m in height and not far off the same in spread, so bear that in mind when choosing a spot to plant it. You also don’t want to pick a variety that’s already taller than 1m before transplanting it to your garden, since this could run the risk of the foliage growing more quickly than the roots. Indeed, many people prefer to plant eucalyptus trees in pots rather than the ground due to their sensitivity to British frosts. This facilitates easy movement if they do need to be moved to sunnier spots or even indoors. 6) Lavender A comprehensive calming solution There’s nothing quite like the persistent buzzing of a mosquito to set your nerves on edge. So why not drive away their presence with one of the most calming horticultural essences known to man? Lavender has long been associated with instilling a sense of serenity in those exposed to its delightful aroma. It’s for this reason that it’s a common ingredient in many creams, lotions and scented candles. Despite this, and the fact that it’s irresistible to bees, butterflies and other pollinators, there are a litany of other insects which can’t stand its fragrance. These include moths, flies, fleas, spiders and – you guessed it – mosquitos, too. “Lavender would be my plant of choice for deterring mosquitoes,” says Master Horticulturist Colin Skelly. “Although, I fear I may have to sit in amongst it in my garden in summer to deter the mosquitoes. “Even if it wasn’t entirely successful, the calming smell would ease the irritation.” 7) Lemongrass Mosquitos presumably can’t stomach a good curry Perhaps most famous in the UK for its starring role in Asian (particularly Thai) cuisine, lemongrass is a great addition to curries, teas and soups. However, the citral oil found inside the plant is anathema to mosquitos, too. With that in mind, placing lemongrass around the home and garden is an excellent way to keep your property mosquito-free. Just be aware that due to its exotic origins, it won’t tolerate British winters well at all, so it’s best to keep it in containers to allow for easy transportation indoors during the colder months. While we’re on the subject of lemon plants, lemon balm, lemon thyme and lemon verbena are all other effective mosquito repellents that contain citral to varying degrees, as well. 8) Marigolds Not just a pretty face The distinctive rosette-shaped flowerheads of marigolds are ideal for adding some pizzazz to borders and flowering vegetable gardens. Yet they’re far more than just eye candy for green-fingered enthusiasts – some say they also contain “nature’s pesticide”. That’s because marigolds exude a pungent smell powered by the oil pyrethrum found within their flowers and foliage. Often used in organic pesticides, pyrethrum discourages the presence of not just mosquitos, but plenty of other pests as well.2 Aphids, whiteflies, nematodes and even deer and rabbits will all be repelled by its musky scent, while bees and butterflies find it irresistible. 9) Mint Mojitos not mosquitos Perhaps one of the most instantly recognisable fragrances in the world, mint is commonly used to flavour toothpastes, chewing gums and other cosmetics and culinary items. It’s fantastic in cocktails and salads, too. But while its culinary properties are well-documented, its ability to deter mosquitos is perhaps not quite common knowledge. There are a wide variety of different types of mint, including peppermint and spearmint to name but two, all of which are effective mosquito repellents. However, all mints are likely to spread through your garden like wildfire, so consider planting them in pots to restrict their movement and prevent a hostile takeover. 10) Rosemary Burn rosemary for an extra-effective mosquito deterrent Commonly added to chicken and lamb dishes to add an extra oomph of flavour, the delectable piney scent let off when rosemary is combusted is too much for mosquitos. That’s why burning it on the barbecue or simply by itself is an effective strategy for keeping them at arm’s length. Rosemary does prefer warmer temperatures, making it ideal for indoor cultivation, but it can handle the British climate just fine if treated appropriately. Just make sure it’s already well developed when planting outdoors and choose a sunny but sheltered spot that benefits from well-draining soil. If you haven’t found what you’re looking for, you may also be interested in our list of plants that deter bugs. References 1. Torgan, C. (2013, December 16). How Mosquitoes Detect People. National Institutes of Health (NIH). Retrieved March 21, 2023, from https://www.nih.gov/news-events/nih-research-matters/how-mosquitoes-detect-people 2. Liu, F., Wang, Q., Xu, P., Andreazza, F., Valbon, W. R., Bandason, E., Chen, M., Li, H., Feng, B., Smith, L. B., Scott, J. G., Takamatsu, G., Ihara, M., Matsuda, K., S, K. J., Coats, J. R., Oliveira, E., Du, Y., & Dong, K. (2021). A dual-target molecular mechanism of pyrethrum repellency against mosquitoes. Nature Communications, 12(1). https://doi.org/10.1038/s41467-021-22847-0
Learn more
Rid Your Garden Of Aphids - Gardeners Share Their Homemade Recipes And Solutions
IN THIS GUIDE Why Are Aphids Damaging For Plants? Signs Of Aphids Which Plants Are Most Vulnerable? 1) Typical Treatment 2) Homemade Remedies 3) Using Natural Predators 4) Chemical Formulations Why You Shouldn’t Use Pesticides Ants: Aphids’ Bodyguards Preventing Aphids Rid Your Garden Of Aphids! References Aphids are among the most prevalent and destructive of garden pests, and they also breed very rapidly. Aphids suck the sap – the lifeblood – out of plants, thereby quickly debilitating and even killing them. Fortunately, with some homework and perseverance, you can eliminate these pests. We outline numerous aphid-control methods including manual ones, home remedies, biological controls, and chemical formulations. Why Are Aphids Damaging For Plants? There’s good news and bad news about aphids. First the bad news: aphids can cause horrendous damage to plants and even kill them. But the good news is that the casual gardener has recourse to numerous methods of different kinds to control, and even eliminate, aphids, commonly called ‘greenfly’ and also ‘plant lice.’ Aphid species number over 5,000 of which more than 500 are found in the United Kingdom.1 Many of them are extremely destructive to some or another set of members of the Plant Kingdom, including agricultural crops, food crops, trees, and all types of ornamental plants, bushes, herbs, and vegetables. Many aphids are identified by the particular plants or trees that they prefer to attack, such as Raspberry aphid, Lettuce aphid, and Beech aphid, to name just one example each of aphids that infest a fruit, a vegetable, and a tree. Many are polyphagous; these attack a large number of plant species. No matter what the type of aphid, they have two attributes in common: they breed and multiply very rapidly, and they suck the sap from plants, debilitating them very quickly and even killing them. Furthermore, some aphids on certain plants are vectors for viruses which themselves sicken and severely damage plant life. The present article is written with the goal of covering the topic of controlling and eliminating aphids in the fullest possible breadth; in turn, this means that no one method is discussed in full depth. We encourage the reader who is interested in a particular method to explore it further. Signs Of Aphids Symptoms of aphid attack include slow growth and stunting, contortion and deformation of leaves, dripping of sap, yellowing and browning of foliage, overall wilting and loss of vigour, and, eventually, death of the plant. More often than not colonies of these tiny pests are visible on the underside of leaves, but they also occur on their upper surfaces, the stems, and sometimes even on the flowers. They are usually yellow-green but are also brown or black. Which Plants Are Most Vulnerable? Some flowers, herbs and shrubs are just more vulnerable than others to aphids. Jasmine, rose, dahlia, hibiscus, chrysanthemum, tomato, (plain) mint, basil, lettuce, beet, cucumber, peas, and gooseberry are some examples. Several kinds of trees are also very vulnerable to aphid infestations. If you have such aphid-susceptible plants in your garden, one of the best steps you could take against aphids is to catch them early. If you have a small garden, you could make it a practice to inspect different samples of plants (including the undersides of selected leaves at all levels) periodically, say every week or every ten days for aphids. The beginning of summer is the time to be on highest alert, as Master Horticulturist Colin Skelly shares: “Early summer is definitely the time of aphid population explosion as conditions for feeding and breeding rapidly improve as plants begin to grow in earnest. “As the season progresses this tends to settle with more isolated outbreaks here and there as predator populations rise to meet the opportunity of the aphid population surge. “I use insecticidal soap if an outbreak is severe or even just blast off with water. This won’t eliminate aphids, but this is the object. “I’m only trying to prevent the worst impacts until harder growth commences (less sappy) and predator populations rise.” Underneath we outline three common methods for dealing with aphids: 1) Typical Treatment If you spot any, crush the pests and also the eggs. “If I have problems with aphids on my plants, I just brush them off with my finger,” shares Organic Gardener Val Bourne. Hosing off the aphids will remove them but will not kill them. Instead, spray soapy water, made from a pure organic soap, on the pests which will kill them in short order. You can wash away the soap residue from foliage in a couple of days. If you do so, aim for the morning hours on a sunny day. Finally, if you catch a localised infestation early (that is before it has had a chance to spread) simply prune or otherwise remove the affected parts of the plant. Put these on a plastic sheet a safe distance away, spray well and all around with any insecticide that will kill aphids, and promptly remove from your garden. 2) Homemade Remedies Those who come from horticulturally-inclined families often inherit pesticide recipes from grandparents, great-aunts, and the like. We list a few homemade recommendations in this section. Pastes, Oils & Powders Solutions of garlic and oregano paste or powder are potent deterrents for most kinds of aphids. In fact, a solution of both the veg and the herb could be made. Tea tree, peppermint, eucalyptus, or anise essential oils are also excellent for combating aphids. A suspension could be made of any combination of these essential oils. They must be appropriately diluted otherwise they will injure plant life. A one to three percent dilution is typical. Rapeseed Oil Rapeseed oil is a potent pest-killer. Make a solution of it at a 1:16 to 1:20 dilution and spray it on aphids, it will kill them within minutes. If you cannot find rapeseed oil, then substitute with Canola oil. Diatomaceous Earth Diatomaceous earth kills all kinds of insects but one seldom finds bees or other pollinators on the undersides of leaves which are aphids’ preferred – though not exclusive – nesting places. Simply prepare a solution – actually a suspension – of diatomaceous earth, and spray it on and around aphids. After the aphids have died you may wash off the sprayed areas. Applying Homemade Remedies Once treatment with any of these solutions is started, it should be followed up with repeat applications every two or three days until there is no sign of aphids. Also inspect your lawn, the ground, and other plants in the vicinity in case aphids have sheltered elsewhere. Only those parts of the plant that are infested with aphids should be treated. You may wish to apply the solution in question to a small part of the plant first to see how well the plant tolerates it. These homebrew solutions and suspensions have three big advantages over many commercial compounds. Used in the proper concentrations: They will not harm bees or other pollinators They are safe to use on vegetables and herbs And they are derived from plant life! Though diatomaceous earth is probably not one of great-aunt’s remedies, we’ll close this section with a mention of it. 3) Using Natural Predators “Rely on your ecosystem and the food web, as bugs are very fragile creatures,” says Val. “So many animals eat the bugs you don’t want in your garden, so trust the wildlife in your spaces and don’t use chemicals.” Aphids will be eliminated and will not be able to establish any colonies in your garden if you release and try to nurture green lacewings, ladybugs, aphid midges, and/or parasitic wasps. “I garden organically and with nature, so I manage pests by making sure that the ecosystem is as complete as possible so that there is something to eat them,” shares Naomi Slade, Garden Writer. Any and all of these beneficial insects, which are a type of biological control, can be bought and released in the garden. However, as they, especially ladybugs, may decamp quickly, efforts to keep them happy in your garden will be necessary.2 “Try and avoid getting rid of aphids completely,” shares Florist Georgie Newbery. “If you have aphids you’ll get ladybirds. Ladybirds won’t come to your garden if they have nothing to eat.” Green lacewings and ladybugs feast upon – besides various garden pests – aphids quite indiscriminately, quickly reducing their populations, eliminating them, and discouraging them from establishing any colonies. Green Lacewings Green lacewings are far more effective than ladybugs as they are not as affected by wanderlust as are ladybugs, and, per insect, eat up many more aphids than ladybugs and do it much faster as well. Parasitic Wasps Parasitic wasps are specialised to prey upon a specific, somewhat narrow, range of aphids. However, because of the way parasitic wasps’ eggs are laid and the fact that their larvae prey upon aphid eggs, aphids are exterminated ‘at source’ – they cannot even reproduce. Gall Midges While aphid midges, also known as gall midges, do prey upon aphids, their beneficial effects are negligible. It is actually midge larvae that prey upon aphids ‘in quantity’, so to speak, so it is your midges’ offspring that will do the aphid extermination. Research has shown that the efficacy of aphid midges through their larvae is strongly dependent upon the presence or absence of other pests, such as thrips. Retaining Beneficial Insects So how to retain these beneficial insects in your garden, or even attract them? “If you want to encourage wildlife and insects like butterflies and hoverflies, it is important to make sure that every stage of their life is catered for,” shares Naomi. “Nectar is no good to a caterpillar or ladybird, so find out what it eats and grow that. “Enriching the soil with organic matter will underpin the entire system, as it allows microorganisms and soil fauna such as earthworms to thrive, and these will feed the individuals higher up the food chain.” In addition to this, you could apply a solution of sugar and honey to plants affected by aphids, set up this solution close by in insect bait trays or petri dishes, or both. Doing so will retain ladybugs and may very well even draw them to your garden. Do not fill the trays or dishes too deeply as feeding insects often get stuck and drown in sticky liquids. To retain and attract green lacewings, keep pollen-producing and/or nectar-rich plants nearby. Dandelion, fennel, mint, shasta daisy, clover, salvia, hyssop, lavender, caragana, scabiosa, and hibiscus are good choices. Finally, apply wheast to, or set it up (as described above) close to, aphid-affected plants. Wheast will retain and also draw ladybugs, lacewings, and other beneficial insects.3 Wheast can be prepared at home or purchased from reputable makers. Do not use chemical formulations, with the exception of targeted applications of insecticidal soap, in conjunction with biological controls as most chemicals will repel or even kill beneficial insects. 4) Chemical Formulations All of the chemical products and formulations mentioned below are organic or are otherwise safe if applied per directions. Insecticidal Soap is a non-chemical preparation that is made of potassium salts of fatty acids. It is easy to mix, easy to apply, effectively kills aphids and can be used on all types of plants. We suggest it be your first line of attack on the chemical-controls front. BotaniGard ES is a chemical product. It is authorised for use but it is potentially toxic to bees and, therefore, it is recommended that it not be applied if bees are nearby. It is also toxic to aquatic life. A 0.4 percent solution of BotaniGard ES will suffice to kill aphids. Neudorff BugFree Bug & Larvae Killer, Resolva Bug Killer, Provanto Smart Bug Killer, and Provanto Ultimate Bug Killer come in spray bottles and are ready to use – no mixing required. They are all very effective against aphids though they have different active ingredients. They are lethal to different sets of garden pests, and they also have somewhat different properties. For example, one will be longer-lasting while another will kill aphid eggs and larvae, besides the pests. One will be best for a few particular edible plants while another will be suitable for a very wide range of veg and herb. We suggest that you look into these and use one to see which one works best for you. Bear in mind that most of these chemical formulations will also have some or another adverse impact on beneficial insects so they should not be applied at all indiscriminately. They should be applied in a targeted manner. As well, chemical products and biological controls should not be used at the same time, other than after thorough research on a product-and-insect basis as outlined above. Why You Shouldn’t Use Pesticides You may read elsewhere about the efficacy of certain products and compounds. Well, those products and compounds do indeed very effectively kill aphids; unfortunately, they are at least toxic and are even extremely poisonous every which way to Tuesday, and have been withdrawn or banned either under British or EU regulations. Withdrawn or not, chemical pesticides have a wide-spectrum action and kill beneficial insects and pollinators, besides aphids and other pests, as Val explains: “Aphids underpin lots of creatures in your garden and will keep them in control. “When you use chemicals, you’re actually killing a lot more than the aphids you are trying to target. Chemicals can end up in water sources too and harm wildlife that way.” Effects Of Non-Recommended Chemicals Keep in mind that approved greenhouse fumigants based on permethrin, a synthetic pyrethroid, are not meant to be used in open gardens. They may be used inside greenhouses. For a current list of pesticides that are not permitted in the United Kingdom, please refer to the Health and Safety Executive’s webpage on regulating pesticides in the UK after Brexit.4 “Don’t use herbicides and pesticides, instead opt for alternative methods of control and leave insects, such as aphids, alone as much as possible to provide food for other insects and birds,” concludes Garden Writer Nic Wilson. “I find problems often resolve themselves without causing too much damage to plants, particularly once healthy garden ecosystems become established.” Ants: Aphids’ Bodyguards Garden ants and aphids have a well-known symbiotic relationship, and this relationship may defeat your efforts to eradicate aphids by deploying beneficial insects.5 Aphids are (among the) honeydew-secreting insects that are ‘tended’ by ants. Garden ants tend aphids by stroking the pests with their antennae to stimulate them to secrete honeydew, which the ants collect. Ants feed on honeydew, and also carry it to their nest for the queen and the larvae. In turn, ants protect aphids, doing so by attacking and killing ant predators including lacewings and ladybugs. Obviously, ants’ bodyguard function for aphids can defeat your efforts to control the pests using beneficial insects. Therefore, prior to releasing or trying to attract such insects, you should determine whether your garden has an ant’s nest or has ants in large numbers. If so, you will probably need to get rid of the ants first as most likely they will already be protecting the aphids. If not, then after you release beneficial insects, monitor their numbers and stay on the lookout for garden ants that may be preying upon them. If you spot such ant activity or a decline in the beneficials’ numbers then you should move to eliminate the ants. Garden ants can be tackled in many ways. Preventing Aphids Water At Soil Level One preventive course of action that can be taken where aphid-susceptible plants are concerned is never to water from above and always to water at soil level. If you ever think that the foliage could use a good wash, then water them from above in the early morning on a day forecasted to be dry, warm and sunny. Companion Planting Another preventive step is to grow aphid-repellant plants. Herbs and shrubs that are odorous and aromatic tend to repel aphids. These include garlic, onion, shallot, chives, dill, and turnip. The pungency of spearmint, peppermint, and catnip are also off-putting to these pests. Finally, some flowering plants such as petunias, geraniums, and marigolds are not only resistant to aphids but also keep them away from nearby plants that do not share these properties. Any of these (or some other) aphid-repellant plants will make a first-rate companion plant for some or another aphid-susceptible plant. Though you can pair any of the deterrent plants, named above, with vulnerable plants, some combinations of companion plants will be particularly effective and are recognised to be so. For example, garlic with roses, and chives with lettuce. Companion plant gardening is a horticultural sub-science in itself. While companion plants greatly aid in pest control they also serve sundry other purposes. Attract Predatory Insects Finally, try to make your garden attractive to beneficial insects that prey upon aphids. These include ladybugs, green lacewings, aphid midges, and parasitic wasps (which are not harmful to humans). A thriving colony of these gardener’s friends will go a long way toward preventing aphid attacks. Rid Your Garden Of Aphids! As mentioned, aphids are very serious garden pests and rapidly destroy plants. And they breed very rapidly as well. But the fact from which to take heart is that they are not one of those dreadful pests for which lay gardeners have no controls or remedies, further to which they are not even particularly strong. If you do some homework, try to choose the right aphid-control method, act as quickly as you can, and persevere with your efforts diligently, it is almost certain that you will win your fight against aphids. References 1. Mahr, S. (n.d.-a). Aphids in-depth. Wisconsin Horticulture. Retrieved March 17, 2023, from https://hort.extension.wisc.edu/articles/aphids-2/ 2. Fosdick, D. (2018, July 10). Ladybug, where have you gone? Aphid fighters tend to roam. Phys.org. Retrieved March 17, 2023, from https://phys.org/news/2018-07-ladybug-aphid-fighters-tend-roam.html 3. Flint, M. (2014, May 14). Lady bugs need special care to control aphids in the garden. ANR Blogs. Retrieved March 17, 2023, from https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=13933 4. Regulating pesticides in the UK after Brexit. (n.d.). Health and Safety Executive. Retrieved March 17, 2023, from https://www.hse.gov.uk/pesticides/brexit.htm 5. McVean, A. (2017, August 16). Farmer ants and their aphid herds. Office for Science and Society. Retrieved March 17, 2023, from https://www.mcgill.ca/oss/article/did-you-know/farmer-ants-and-their-aphid-herds
Learn more
Are Your Rhododendron Leaves Wilting And Drooping? Horticulturists Explain Why
IN THIS GUIDE 1) Cold Or Windy Weather 2) Broken Stems 3) Water Shortage 4) Waterlogging / Excessive Watering 5) Fungal Infection 6) Vine Weevils Or Other Insect Pests References Rhododendron are typically easy to care for and low maintenance, but there are a range of issues that can cause leaves to start wilting and drooping. In this article, we will explore some of the most common issues which can cause rhododendron leaves to wilt and droop. “In addition to producing every possible flower colour, many rhododendrons are fragrant and have beautiful foliage,” says Katrina Clow, Hon. Secretary of The Scottish Rhododendron Society. “They can become trees or remain diminutive little plants and so can suit many types of garden.” 1) Cold Or Windy Weather Many rhododendron are hardy and can easily make it through the winter in the UK. However, some cultivars may well show signs of stress in cold temperatures, especially in windy weather over the coldest months. They will sometimes simply recover after milder conditions return. If leaves are curling in on themselves this may just be the plant’s natural response to cold, exposed conditions, known as thermotropism.1 Rhododendrons curl leaves inwards so that less of the leaf surface is exposed to drying cold winds. This is the plant’s defence mechanism to prevent too much water evaporating from the leaves. The rhododendron may need water, if conditions have been dry, and you should make sure that you conserve that water by laying an organic mulch around the base of the plant. “We cannot control the weather!” exclaims Katrina. “Moist, humid and mild conditions will help prolong flower life. A late May frost or a sudden gale can destroy all the loveliness of your rhododendrons.” Despite this, if you encounter this issue frequently, you may need to consider replacing your shrub with a more cold-hardy cultivar better suited to your location. 2) Broken Stems If the leaves are wilting and drooping only on one side or a certain portion of the plant, the first thing to check for is broken or damaged stems. Of course, leaves will wilt and droop if water and nutrients cannot pass up the stems to reach them. Katrina recommends foliar feeding your rhododendrons in the growing season to make sure your plants get all the nutrients they need. Physiological damage may have been caused not by a more pernicious issue but simply by storm damage or other extreme weather conditions – especially if your shrub is in an exposed location. Be sure to prune out the damaged section as soon as possible to avoid putting excess strain on the rest of the plant. But note, if water is not reaching the leaves effectively, there can be a range of other reasons for this – which we will cover below. 3) Water Shortage Another common reason that leaves on a rhododendron will wilt and droop is issues relating to water. In dry summer months, you may find that water shortage is the culprit. Rhododendrons have shallow roots and require moist soil. Make sure that you are watering sufficiently, and with sufficient frequency during dry periods. “Spray the foliage with rainwater if required,” Katrina suggests. Remember that smaller cultivars growing in containers will have higher water needs. Moisture is especially critical in the middle of summer to help flower bud production for the following year. A dry summer can seriously hinder flowering. “Large rhododendrons may be more prone to a lack of water in pots,” adds Master Horticulturist Peter Lickorish. “If potting into something larger or planting out is not an option, they can be pruned to help them manage water. “However, as they flower on older stems, pruning must be carried out minimally over several years to avoid a dent in blooming.” 4) Waterlogging / Excessive Watering Wilting and drooping leaves can also unfortunately be a sign that you have watered too much. Rhododendrons do need moist soil, as mentioned above – but they will not do well when the soil or growing medium becomes waterlogged. During heavy rains, soils that do not drain freely may cause a problem for rhododendrons. Make sure that you improve the soil structure with the regular application of organic mulch, which will aid in building a healthy, aerated, moisture-retentive yet free-draining soil. If growing rhododendron in pots or containers, make sure that you have chosen an appropriate moisture-retentive yet free-draining ericaceous mix. Make sure that the container you have chosen is allowing water to drain out the base. 5) Fungal Infection Unfortunately, waterlogged conditions can increase the likelihood of a fungal infection taking hold, and fungal infection could also be the cause of your rhododendron leaves wilting and drooping. Phytophthora Root Rot One of the most common fungal infections is Phytophthora root rot. Spores come in with plants introduced to your garden, or on the wind. Sadly, once you see this problem in the leaves, the disease is likely to be quite advanced in the roots. If you unearth the roots you will likely see much evidence of decay if this is the problem. However, it may be difficult to tell whether prolonged waterlogging alone has caused this issue, or whether fungal disease is present. Honey Fungus Rhododendron may also suffer from honey fungus. This is another fungus that attacks the roots of a number of woody perennial plants. If this fungus is present, this will also cause root death before you are aware of wilting and drooping leaves. If you look at the roots and find a white mycelium (which smells strongly of mushrooms) around the roots and the base of the shrub, this is likely to be the problem. When one of these fungal diseases is present, you should carefully dispose of the plant and replace the topsoil from the root area. Susceptible plants should not be grown in the same area and you should replant with more resistant species. 6) Vine Weevils Or Other Insect Pests Vine weevils and other insect pests can also cause rhododendron leaves to wilt and droop. This can be a problem, especially, for rhododendrons which are grown in containers. Adult vine weevils will nibble the edges of rhododendron leaves, but it is the grubs that pose a more serious problem – they feed on plant roots over the autumn and winter months, causing wilting and eventually death of the plant. You can deal with vine weevils by picking the grubs from the compost or potting soil by hand. This may be time-consuming but try to make sure you remove as many larvae as you can. There are also biological controls available. You can introduce nematodes: Heterorhabditis megidis, H. bacteriophora and Steinernema kraussei are amongst those commonly used. These are usually applied in August or early September, but may also be applied in late spring. If your rhododendron leaves are wilting and drooping, the problem usually relates to water. For some reason, the leaves are not getting the water and nutrients they need. Rule out environmental problems before deciding whether disease or pest species are causing the issue. Working through the list above should usually give you an answer to your question. References 1. Van Zanten, M., Ai, H., & Quint, M. (2021). Plant thermotropism: an underexplored thermal engagement and avoidance strategy. Journal of Experimental Botany. https://doi.org/10.1093/jxb/erab209
Learn more
