Growing
Ground Elder: This Problem Plant Can Actually Be Useful If You Control Its Spread
IN THIS GUIDE What Is Ground Elder? Why Is It A Problem? How Did Ground Elder Get Into Your Garden? How To Identify It Removing Ground Elder How To Dispose Of Ground Elder Safely References Ground elder is a problem that could turn into an opportunity. This well-known weed is hard to eradicate, but you should ask yourself if you really need to get rid of it completely… It is often considered to be one of the most problematic garden weeds, as it is very difficult to get rid of. However, as we will explain in this guide, while we may not always want it in certain spots and will likely want to control it carefully, it can be a very useful plant to have around. What Is Ground Elder? Ground elder is a flowering perennial in the Apiaceae (carrot) plant family called Aegopodium podagraria.1 It is also known by a number of other names, such as ‘Herb Gerard’, ‘Goutweed’ and ‘Bishop’s Weed’. The name ground elder does not come from any familial relationship to the elder plant (Sambucus), but rather from the superficial similarities between the foliage and flowers of these two plants. The plant is native to mainland Europe and parts of Asia and is believed to have been introduced to the UK from the continent in the Roman era or perhaps by monks during the middle ages.2 Why Is It A Problem? Ground elder is largely considered a problem because of its propensity to spread rapidly and to outcompete other plants. As a perennial plant, it will not die over winter and will come back year after year. Ground elder can spread very rapidly by means of rhizomes below the soil, which spread out for long distances and delve deeply below the soil. When cut, these rhizomes can grow into new plants from even the tiniest fragment. The plant can also spread by means of seeds if the plants are allowed to flower. How Did Ground Elder Get Into Your Garden? Though ground elder can spread by seed, it is most commonly introduced to gardens accidentally by rhizomes which spread under fence lines, hedges or because tiny portions of the plant were imported in composts or manures. How To Identify It Ground elder is usually first spotted in spring when young shoots with furled leaves burst up through the soil and open out. These leaves look like the leaves of an elder tree and, if you try to pull them up, you will find it is connected to a long white rhizome system. In late spring and summer, tall stalks will appear, which support flat umbels of white flowers which look a little like elderflowers. Removing Ground Elder When gardeners are faced with beds taken over by this weed, the first instinct will usually be to remove and kill it altogether. However, eradicating this plant entirely can be challenging and may not always be beneficial. Instead, it can be beneficial to consider the uses of this plant and to control its further spread using organic methods. 1) Organic Methods I have ground elder in my forest garden and around the edges of other parts of my property, as it was here when we moved in. Rather than seeing it as a problem, I view it as a useful plant, as this is one of the edible weeds which I value on my property. As they first unfurl, the young leaves from the soil make a great stir fry in spring and our chickens also eat them. Both our own harvesting and the chickens foraging helps to prevent this plant from spreading too excessively, but where it does grow, I mostly find it a useful ground cover plant. On occasion, the ground elder will find its way to the edges of a cultivated area where I would prefer it not to spread. When the shoots emerge, I carefully trace back and remove the rhizome and plant from the soil. Manual removal can work for small spaces, but you do have to be careful and make sure you remove all the rhizome since, as mentioned above, the plant can regrow from even the smallest piece. To eradicate ground elder from a larger growing area, you will need to remove and temporarily rehouse any other plants that you wish to keep, then carefully pull up the ground elder, trying not to break the rhizomes. “Wash the roots of any plants you have lifted and carefully untangle any rhizomes growing through them,” explains Peter Lickorish, a Horticultural Consultant. Afterwards, sift through the soil judiciously to make sure it does not contain any more pieces, before replanting your chosen plants. Some people will use black plastic sheeting to cover the soil, though I would not recommend this method, as the soil below will be degraded by this and soil life will be impacted. In any case, the black plastic would have to be in place for several years to be effective. In either case, if there is ground elder on an adjacent property, it will come back. You will need to sink a barrier that descends to at least 50cm below the soil to prevent this, perhaps even more. So, the best option is usually to tolerate the presence of ground elder and even learn to value its presence. 2) Growing Plants To Smother It Ground elder creeping in around the edges of a garden can be less problematic if you simply embrace its presence and restrict its thuggish growth by growing other plants which can compete with it and deduce its preponderance. Many woody shrubs or trees, which can cope with the same conditions of shade, will be perfectly happy growing amid ground elder and, through the competition and increased shade, will somewhat restrict its growth. Planting vigorous ground cover plants can also help in outcompeting ground elder and making sure it does not take over entirely. Some plants to try in an area where ground elder is creeping in are Acanthus mollis, hardy cranesbills, Ajuga and – in larger spaces – very vigorous ground cover shrubs like Rubus tricolor and other ground cover raspberries. Mint is another good ground cover for shade which can happily co-exist with ground elder, and alpine strawberries can be another good choice. Ground elder will likely still emerge between other plants, but the overall effect can be pleasing and great for wildlife. As well as enjoying an edible yield in spring, the white flowers can also be very visually pleasing in a shady spot. In a lawn or grassland, ground elder will gradually be reduced by mowing. 3) Chemical Methods Chemical weedkillers are rarely effective in eradicating ground elder entirely and, of course, bring huge environmental and health concerns. Keep your garden organic and learn to live with weeds, and your garden will be much healthier and will continue to be beautiful and productive over the years to come. How To Dispose Of Ground Elder Safely When pulling the ground elder stems, leaves and rhizomes from the ground, remember that this material should not be added to a composting system. Instead, place everything into a bucket of water, along with other weeds, to make a liquid plant feed. Once they have rotted down in the water, you can safely add the strained goop to your composting system and use the liquid as a multi-purpose feed. You can also place the material somewhere to dry out and then burn it along with woody material. The wood ash can also be used in moderation in your garden. References 1. Aegopodium podagraria L. (n.d.). Kew Botanic Gardens. Retrieved May 24, 2023, from https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:5849-2 2. Ground-elder. (n.d.). Gloucestershire Wildlife Trust. Retrieved March 27, 2023, from https://www.gloucestershirewildlifetrust.co.uk/wildlife-explorer/wildflowers/ground-elder
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7 Common Cacti Problems And Solutions Shared By Nursery Growers
IN THIS GUIDE 1) Overwatering Or Poor Drainage 2) Underwatering 3) A Lack Of Light 4) Excessive Brightness 5) High Humidity 6) Cold & Wet Winter Conditions 7) Sap-Sucking Pests There are many cacti that can be grown as houseplants in the UK and even a few that are hardy enough to be grown outdoors in our climate. These are fascinating plants adapted to dryland or desert growing conditions. It is the ways in which these plants have adapted to low rainfall environments that dictate how they are cared for and where they are best grown. Whichever cacti you are growing and wherever they are placed, it is important to pay attention to the needs of these plants and to understand what they require. Most of the most common problems and issues when growing cacti are caused by: Overwatering or poor drainage. Underwatering. A lack of light. Excessive brightness. High humidity. Cold and wet conditions in winter. Sap-sucking pests. As you can see, many of these problems and issues can easily be avoided or tackled by placing a cactus in the right spot and caring for it correctly. Read on for a more in-depth discussion of the different things that can cause problems with these plants and their subsequent solutions. 1) Overwatering Or Poor Drainage “I grew up in California amongst vineyards, orchards and cactuses,” says Alley Marie Jordan, a garden historian. “Instead of a hedge like most UK houses have, we marked our garden with cactus walls and palm trees. “In California, you have to search for shade and water access, whereas in the UK you plant for good drainage and look for sun!” Since cacti are adapted to very dry environments, some of the most common problems relate to overwatering or poor drainage. It is important to make sure you do not overwater a cactus because this can damage the plant roots, cause growth to be stunted, lead to blistering and rot can set in. These plants require free-draining conditions and as well as making sure that you do not overwater, you also need to make sure that drainage is excellent at all times. “This can be achieved by generously mixing horticultural grit with compost and ensuring drainage holes are present and not likely to clog up,” shares Master Horticulturist Peter Lickorish. Excess water must always be able to drain away freely, otherwise, when left in standing water or boggy conditions, the roots can often rot. When thinking about how much water plants need, you should always consider the native environment of the plants you are watering, as Daniel Jackson, the Owner of Ottershaw Cacti, explains: “Their native environments are often very dry, such as the bright and hot lands of South Africa and Mexico, not the naturally soggy lands of Surrey!” The amount and frequency of rainfall in their native range will help you understand how much water they will require and the frequency with which they should be watered. “Only water after the soil has dried out and reduce this in the winter months,” says Darren Evans, the Plant Manager at Pugh’s Cacti. 2) Underwatering However, do not think that because cacti come from desert environments, they do not need to be watered at all. Of course, cacti can be very drought tolerant, but they do need some water. Under-watering cacti can lead to shrivelling and the growth of the plant may slow considerably or the new growth might be misshapen. “Increase watering as the weather warms in spring and only reduce watering in the Autumn,” advises David Ennals, Owner of Coach House Cacti. 3) A Lack Of Light If cacti do not get enough light, they can also end up being weak and misshapen. Indoors, cacti will generally need a bright spot, but one out of direct light. Outdoors, hardy cacti will typically need a sunny spot that is as warm and sheltered as possible. “We often get asked ‘why does my plant look like this?’ and it’s usually due to insufficient light levels on a window sill inside the house,” Tom Adkin & Giulia Consolandi from Piccolo Plants Nursery share. “Look into the natural environment that the plant would grow in and you will soon find the perfect spot for it.” 4) Excessive Brightness Cacti generally need a bright location when grown indoors but can encounter problems in intense direct sun. Too much sun is one potential cause of a problem known as cactus corky scab. This problem causes brown spots to arise on the skin of the plant, which gradually form into calluses or scabs shrunken into the surface. Move the plant out of intense sunlight and the problem may resolve itself. 5) High Humidity Cactus corky scab can also be caused by high humidity, so it is important to work out whether too much bright sunlight or too high a humidity level is to blame. Reducing humidity within your home might allow you to solve this problem when growing cacti as houseplants in our humid climate. “For this reason, some combinations of houseplants just do not work well, such as cacti and most orchids, because the humidity cannot be at the right level to please both,” says Peter. 6) Cold & Wet Winter Conditions “After the growing season, cacti are usually ready for a rest, so, during the winter months, require time to recover and get through the colder months,” says Darren. “Because of this, make sure indoor-grown cacti are not kept by a radiator or heater throughout the winter. “As a general rule, keep your cacti at around 10°C from November to February.” For hardy cacti that are grown outside in the garden, cold temperatures can cause dieback on the plants and create patches of discolouration on their skin. However, the main problem for gardeners who have cacti outside over the winter months is not the cold, but the wet. Even cacti that can withstand colder temperatures will often need to be protected or brought indoors due to the high levels of precipitation in the winter months. Growing under a porch may be the solution. “Balancing moisture and temperature is important,” shares Peter. “Remember that cold air can hold less moisture, so the relative humidity increases. This could be a real problem for overwintering cacti, so remember to select somewhere dry and keep humidity low through ventilation. “However, avoid draughts. In a greenhouse, opening up the doors and vents on a warm winter day can help remove residual moisture. In a larger greenhouse, low vents or louvres could be opened slightly to circulate air, but keep cacti on shelving away from draughts.” 7) Sap-Sucking Pests This final category of problem is a little different to all of the above because this is a problem that can arise regardless of where you place a cactus and the care you provide. A number of sap-sucking insects can potentially take an interest in cacti and can cause a serious problem in larger numbers. These can include scale insects, red spider mites and mealybugs, all of which can be common problems when growing indoors or under cover in a greenhouse or polytunnel. The key thing is to remain vigilant and nip any pest problems on houseplants in the bud before they get out of hand. Treatments based on oils and soaps, sold for houseplants, can work well. These key problems and issues listed above are not uncommon when growing cacti, but are largely easily avoided. As long as you place cacti in the right environment and provide the right environmental conditions, you should still find that even though issues can arise, these plants are incredibly forgiving and relatively easy to grow.
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Himalayan Balsam Is Highly Invasive And Spreading Fast: How To Halt Its Spread
IN THIS GUIDE About Himalayan Balsam Identifying Himalayan Balsam Is Himalayan Balsam Invasive? How Do These Plants Disperse Their Seeds? How To Control Himalayan Balsam Plant Disposal Composting Himalayan Balsam References Himalayan Balsam is very robust and pretty, but it is just as undesirable. Of montane origin, this tough annual rapidly grows to overhead height. It bears a profusion of unusual and undeniably lovely bright pink flowers that are set off by light green foliage on a well-branched form. Unfortunately, it is an aggressive alien species that is highly invasive throughout Europe. About Himalayan Balsam Himalayan Balsam, formally known as Impatiens glandulifera, is a very pretty and unusual flowering plant originating in the Kashmiri Himalayas north of Pakistan and India.1 Unfortunately, it is an aggressive species that can outcompete native ones and becomes invasive in temperate, tundra and similar climatic zones. Though it is an annual, it is vigorous and propagates exceptionally efficiently, as its nectar draws swarms of bees which, in turn, cross-pollinate the flowers very effectively. It also produces equally copious amounts of seeds, which are dispersed by seedpod explosions (ballochory). A large number of seeds are then scattered around each mature plant, so it is little wonder that Himalayan Balsam steadily colonises good-sized swaths of the ground by forming monoculture thickets. This species itself does not need much sunlight, but because of its own height and its survival strategy of forming dense thickets, it starves other shorter native species of much-needed sunlight, gradually eliminating them. It is also indifferent to the soil, growing in poor as well as rich soils, and light as well as heavy soils, with about equal facility. Identifying Himalayan Balsam It is not for nothing that Himalayan Balsam is often called ‘Policeman’s Helmet’, as the flower’s shape really does bring to mind a bobby’s hat, except for the fact that its colour varies from pale pink through to white. This uncommon flower is somewhat like a flared tube with two flaps. The flowers are borne on racemes and occur in profusion in the summer and autumn on a tall, well-branched shrub that reaches up to 2-3m tall. The flowers emit a strong, sickly-sweet scent. If you see such a flowering plant and further notice that it has light, bright green leaves that are elongated and lanceolate with visible veining and are borne on stems that have a reddish tone, it is very likely Himalayan Balsam. You would encounter Himalayan Balsam on riverbanks, alongside watercourses, near rubbish tips and in waste ground. It also grows on forest and woodland edges, in fields and meadows and around ditches. Is Himalayan Balsam Invasive? Yes. In fact, it has been flagged by the United Kingdom’s Department for Environment, Food & Rural Affairs and the Animal and Plant Health Agency since 2nd August 2017 as a non-native invasive plant species in England and Wales.2 It also appears in the EU Regulation on Invasive Alien Species which remains applicable to the United Kingdom.3 Efforts to halt its spread are underway in several regions of the country and it is often referred to as a weed. “The classification of Himalayan Balsam as an invasive non-native plant species means it must not be planted in the wild and if identified on a homeowner’s land it must be stopped from spreading to neighbouring land,” shares Master Horticulturist Colin Skelly.4 How Do These Plants Disperse Their Seeds? They disperse their seeds by a rather dramatic method of seed capsule explosion called ballochory.5 The pretty flowers develop into seedpods or capsules in autumn. Over time, as moisture from a capsule evaporates, it keeps deforming and eventually explodes noisily, scattering its seeds nearby and even up to 7m metres away. Drying capsules can also explode if they are physically disturbed, sometimes merely touched, by wildlife. Unfortunately, these cunning colonisers also have a secondary method of seed dispersal! As mentioned, Himalayan Balsam plants are fond of growing by riverbanks and watercourses. When such riverine members’ seedpods explode, many seeds fall into the waterway and the flowing water then carries the seeds far and wide. The seeds that are subsequently deposited on the ground then grow into new plants a great distance from the original. This method of seed dispersal is known as hydrochory.6 How To Control Himalayan Balsam From a professional and scientific standpoint, Himalayan Balsam is best controlled systemically by reducing the nutrient-richness of riparian areas and the ground around those waterways that have been invaded by this invasive plant. Doing so affords native species a better chance to compete. Some local plants are able to gut it out in poorer soils a little better than Himalayan Balsam, whereas the latter positively flourish in rich soils near waterways. In the United Kingdom, various regional conservation organisations schedule balsam bashing events, usually in June.7 A group of volunteers walks through areas known to be colonised by the plant, uprooting, cutting and otherwise destroying its stands. Out in the open, strimming is also used and it too is an effective method of control. It is possibly the most efficient method to deal with dense thickets before the plants have started to set seed. Plants should be cut off at the base of the stem. As an individual gardener, your best bets are to uproot the plants and use particular kinds of weedkillers. Both the RHS and the Centre for Ecology & Hydrology recommend uprooting and cutting as the primary methods of effective control.8 The downside to cutting any part of the plant is that if this is done above the first node on the stem, especially before June, nothing will be achieved, as the plant’s strong roots will ensure its survival. All that will happen is that the plant will become bushy. Pulling up these plants, preferably as early as possible in the season, is a better method of control than cutting it. If you pull them up after they have started forming seed capsules, watch out for inadvertent seed dispersal! Lay the uprooted plants on plastic sheets. I. glandulifera can also be controlled by chemical means. Use contact weedkillers on them before they form seed capsules, remembering that the earlier this is done, the better. Recent botanical research has uncovered a very effective and targeted biological control for Himalayan Balsam, a rust fungus named Puccinia komarovii var. glanduliferae.9 This is a Himalayan rust fungus that infects and kills Himalayan Balsam with near-total specificity. It has been discovered and even tested and was subsequently found to attack a few other Balsam impatiens, though it does not affect Western ornamental impatiens, the popular bedding plants. Research is ongoing to identify and isolate a strain of this rust fungus that will be specific exclusively to I. glandulifera. Plant Disposal Burning I. glandulifera is an effective method of halting its spread and destroying it, but burning plants and plant material is subject to somewhat differing regulations in England and Wales, Scotland, and Northern Ireland. Generally, you are required to notify appropriate local authorities in advance of burning plant material, ensure that the burning does not cause pollution or nuisance and that only white smoke, not black, is produced. I’d suggest that before burning any plant material, you acquaint yourself with the local rules and regulations by paying a visit to the website of your district council or environmental office. Composting Himalayan Balsam You might be able to compost your Himalayan Balsam depending on the stage of the plant’s lifecycle. As it is an annual, there is nothing to fear from its roots and you can just let them dry out in the sun. The concern is that its seedpods and seeds may get into the compost heap. The tough seeds may well germinate in the compost or wait until the compost is used, as seeds are viable for around 18-24 months. Either way, a compost of this kind would facilitate the spread of this invasive plant. Keeping these facts in mind, you may compost Himalayan Balsam at any stage of its lifecycle up until the time that buds have started to flower. If any flowers of a plant have withered, do not compost them. You never know if you will be adding seedpods and seeds to your compost. You can search for seedpods and remove them or compost only the foliage, but that would hardly be worth the time and effort. Considering how aggressive and invasive the plant is and the problems that are being faced in trying to limit its spread, I’d suggest that you play it safe and avoid composting Himalayan Balsam. Also, be aware that many localities prohibit the dumping of this and other similar plants into rubbish skips. References 1. Himalayan balsam. (n.d.). The Wildlife Trusts. Retrieved March 17, 2023, from https://www.wildlifetrusts.org/wildlife-explorer/wildflowers/himalayan-balsam 2. Himalayan balsam. (n.d.-b). Public Information on Invasive Species in Wales. Retrieved March 17, 2023, from https://www.gov.wales/sites/default/files/publications/2022-03/himalayan-balsam-public-information-controlling-invasive-species-wales.pdf 3. Invasive alien species. (n.d.). European Commission: Environment. Retrieved March 17, 2023, from https://environment.ec.europa.eu/topics/nature-and-biodiversity/invasive-alien-species_en 4. How to stop invasive non-native plants from spreading. (2022, February 2). GOV.UK. Retrieved June 13, 2023, from https://www.gov.uk/guidance/prevent-the-spread-of-harmful-invasive-and-non-native-plants#:~:text=Types%20of%20invasive%20non%2Dnative%20plants,-The%20most%20commonly&text=Giant%20hogweed,New%20Zealand%20pygmyweed 5. Seed dispersal: 5 ways trees spread seeds. (2019, August 23). Woodland Trust. Retrieved March 17, 2023, from https://www.woodlandtrust.org.uk/blog/2019/08/seed-dispersal/ 6. Craft, C. (2016). Hydrochory. Science Direct, 3–22. https://doi.org/10.1016/b978-0-12-407232-9.00001-4 7. The Big Balsam Bash 2022. (2022, April 14). Groundwork. Retrieved March 17, 2023, from https://www.groundwork.org.uk/bigbalsambash2022/ 8. Himalayan Balsam. (n.d.). Peak District: Gov. Retrieved March 17, 2023, from https://www.peakdistrict.gov.uk/__data/assets/pdf_file/0019/48016/himalayan_balsam_control.pdf 9. Tanner, R., Ellison, C., Kassai-Jáger, G., Varia, S., Djeddour, S., Singh, M., Csiszár, Á., Csontos, P., Kiss, L., & Evans, H. C. (2015). Puccinia komarovii var. glanduliferae var. nov.: a fungal agent for the biological control of Himalayan balsam (Impatiens glandulifera). European Journal of Plant Pathology, 141(2), 247–266. https://doi.org/10.1007/s10658-014-0539-x
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Tackling Aphids On An Acer Tree - Why Organic Solutions Are Always The Best
IN THIS GUIDE Are Aphids A Problem For Acers? Pest Management In An Organic Garden How To Deal With Aphid Infestations Acers, when grown in the right spots, are typically trouble-free trees to grow. However, on occasion, small pest problems can arise. One pest species that you may spot on your Acers is aphids. Are Aphids A Problem For Acers? Aphids are small sap-sucking insects that usually will not be a major issue for Acers. Even if you do see some aphids on your Acer, they will not usually become a big problem, nor dramatically affect the growth or health of the plant. However, they are attracted to these trees and, if you have a major infestation, this can lead to poor or distorted growth. Growing on the honeydew that aphids excrete, you may also begin to see sooty moulds developing. Pest Management In An Organic Garden One thing that it is important to remember in any organic garden is that we need some pests. Aphids, like many other pest species, are important elements in the food chain and are eaten by a range of different wildlife in your space. Without aphids, other beneficial wildlife would suffer and biodiversity in your garden will be lower, which can cause a range of knock-on problems. If you try to eradicate aphids entirely by using pesticides, you can end up with an environment depleted of their natural predators, which is when the aphid population can get out of control. How To Deal With Aphid Infestations To tackle aphids that are present on your Acers, one of the best things to do is to think about how you can make sure your garden is as rich in wildlife as possible. Planting companion plants which attract aphid predators like ladybirds, lacewings and hoverflies around an Acer is the most important step to make sure aphids don’t get out of control. Coriander, yarrow, cosmos and nasturtium are all said to help attract ladybirds naturally. Less Is More If you can, it is best to tolerate aphids on trees like Acers. If your garden has a healthy ecosystem, by late summer, predators should have restored natural balance and kept their numbers in check. Less is often more when it comes to controlling aphids in an organic garden. However, if there are excessive numbers of aphids before natural predation comes into play, you can simply squash these by hand or use a hose to knock them off the Acer that they are damaging. “Aphids are usually a minor problem with Acers,” says Agustin Coello-Vera, the Chairman of The Maple Society. “If needed, you can often control aphids by wiping or spraying the leaves of the plant with a mild solution of water and a few drops of dish soap.” This is a technique mirrored by RHS Master Horticulturist Dan Ori: “Spraying the aphids directly with a solution of non-biological dish soap should block the breathing pores on the backs of the aphids. “The concentration I use is a sixth of a teaspoon of standard concentration non-biological washing-up liquid to 500ml of water; I apply this early in the morning or evening and I would normally rinse off with water after a few hours if the plant is not in direct sunlight, you may need to repeat this over multiple days to bring aphid levels down to a tolerable level.” See this video for a demonstration of the process from Dan himself: Just remember, you should then take steps to prevent a reoccurrence by attracting beneficial predatory insects and other wildlife to your garden.
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Your Chrysanthemum Might Be A Late Bloomer - Check These Reasons For Not Flowering
IN THIS GUIDE 1) Late-Bloomers 2) Lack Of Sun 3) Waterlogged Soil 4) Excess Nitrogen 5) Pests And Diseases Chrysanthemums are cheery flowering plants that work well in beds and borders, while late-flowering types flower in the winter months and can be grown as houseplants indoors. But what if your chrysanthemums fail to bloom? There are a range of reasons why chrysanthemums may fail to flower, but the most common reasons for an absence of blooms are: It is the wrong blooming season for the variety you are growing. Your plant is receiving too little sun. The roots of your Chrysanthemum are growing in overly wet or waterlogged conditions. There is excess nitrogen in the plant’s soil. Pests or diseases may have impacted your plants. Read on for a little more information to help you work out the reasons for this problem. 1) Late-Bloomers Remember, there are different types and cultivars of chrysanthemums and some bloom later than others, as Master Horticulturist Colin Skelly explains: “There are early, mid and late-flowering Chrysanthemums, flowering at different times from August through to November. “I like to grow a range if I can so that I can replace one pot for another as the season progresses from late summer to late autumn. ‘Remember to label your plants and note when it is due to flower.” Make sure you know which type or types you are growing, so you know precisely when you should expect it to bloom. Most hardy garden chrysanthemums will bloom in September and October, but more tender types will flower later, usually over the winter months. 2) Lack Of Sun Often, a problem with non-flowering is due to environmental conditions, such as excessive shade. Chrysanthemums are sun-loving plants, which should ideally be grown in full sun. If they do not get enough sun, they may not flower as well or they may fail to flower entirely. 3) Waterlogged Soil Another environmental problem which can lead to chrysanthemums failing to bloom is excessive water. These plants require relatively free draining conditions, so while they do need the soil or growing medium to remain moist, it is important not to overwater. Make sure that excess water can drain away freely and that waterlogging does not occur. 4) Excess Nitrogen If you have fed your chrysanthemums with a nitrogen-rich fertiliser or plant feed, this can sometimes encourage foliage growth at the expense of flowers. Always avoid synthetic nitrogen feeds and choose organic options. You should feed chrysanthemums with an organic liquid plant feed from late spring, but stop feeding as soon as the flower buds start to open. 5) Pests And Diseases Sometimes, especially where overwatering has occurred, chrysanthemums can develop fungal diseases, such as root rot and mould. White rust is one of the common fungal infections you may encounter. This causes discolouration and problems with the leaves, but where a plant is badly affected, its growth may be stunted and fail to flower. Pests like slugs and snails, aphids, leaf miners and eelworms may also have weakened your plant and stunted its growth, reducing flowering. You can reduce the chances of pest or disease problems by making sure you provide the appropriate growing conditions and care for your plants.
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Sap-Sucking Mealybugs Distort Plant Growth - Here Are Treatment And Prevention Tips
IN THIS GUIDE What Are Mealybugs? Mealybug Life Cycle Mealybug Causes Identifying Mealybugs Quarantining Plants How To Get Rid Of Mealybugs Treatment For Commonly Affected Plants Ongoing Prevention References Mealybugs are small sap-sucking insects that, if given a chance, can damage and severely weaken a wide range of plants. Even though they are difficult to control, there are some measures that can help prevent and limit their spread and destruction. What Are Mealybugs? Mealybugs are a type of soft-bodied insect that are similar and closely related to scale insects. Growing to 4mm long they appear pink or white and are easy to spot as adults, resembling the shape of a woodlouse. Several species of mealybugs are present here in the United Kingdom, with perhaps the most common being in the genera Pseudococcus and Planococcus.1 The glasshouse mealybug, as its name suggests, attacks indoor plants; the root mealybug attacks the roots of houseplants and other ornamentals; the phormium mealybug, which can survive lower temperatures, preys on phormiums and cordylines. “It is easy to think of mealybugs as being so encircled by their own waxy coating that they cannot move, but they can,” says Horticultural Consultant Peter Lickorish. “Their ability to move between plants is what makes the quarantining so important. It’s not just the mealybugs that are mobile. They can carry viruses between plants and their sap-sucking generally weakens and distorts plant growth. “They love the underside of the leaves because that’s where vessels carrying the sugary sap are located. When buying a plant, always have a look underneath the leaves as it’s surprising how many pests live under there.” Mealybugs tend to be most problematic on houseplants and plants grown in a greenhouse or conservatory as they love warm and humid conditions. However, some species can affect outdoor plants, such as phormiums, citrus and hibiscus. Generally pink or grey in colour, they produce a white wax substance that covers their bodies and resembles cotton fluff. “Keep an eye out for the dreaded mealybug, a common pest of the cactus and succulent,” warns Darren Evans, Plant Manager at Pugh’s Cacti. Mealybugs tend to live in small clusters hidden away in the leaf joins and under the leaves, sucking the sap from the plant, which, in turn, is excreted as a sticky substance called honeydew that can attract a sooty black mould. Mealybug Life Cycle The mealybug lifecycle differs slightly according to the species, but generally, new generations are hatched from eggs, although a few bears live offspring. In warm conditions, the female mealybug can lay her eggs all year round, yet this may become less frequent in colder weather. The female can lay anything between 150-600 yellow or orange eggs at a time before she dies, which are protected by a white wax-like coating.2 After 7-10 days, the eggs hatch, producing nymphs which after a month or two of feeding, turn into adult mealybugs.3 The speed of their development increases with warmer weather, or in warm greenhouse conditions. The female mealybug then continues the life cycle, whereas in some species, the male pupates into a winged insect, which dies within days. In a warm indoor climate, up to eight generations can be produced each year, which is why prevention is key wherever possible.4 Mealybug Causes A mealybug infestation can seemingly come out of nowhere, as one day a plant can look healthy and free of pests and disease and the next it is covered with the tell-tale white cotton substance or black sooty mould. The most common cause of mealybugs is bringing home an infected new plant, especially an indoor variety, which is why it is often recommended to quarantine new plants before adding them to a collection. However, mealybugs can also be contracted by placing plants outside during the summer months and by using infected soil. Identifying Mealybugs Mealybugs are quite easy to spot when an infestation has occurred as the white or grey adults are around half a centimetre and their white waxy substance is fairly obvious. However, spotting their eggs is not so easy, as they are small and hatch quickly – producing nymphs. Once the temperature warms up outside in spring (or year-round indoors or in a heated greenhouse) it is advisable to check plants frequently for signs of mealybugs, as once a large infestation is present it is a challenge to eradicate. When checking plants, pay careful attention to the leaf axils and the underneath of the foliage, as this is where they are likely to be found. Quarantining Plants Since mealybugs are often introduced through a new plant, it is advisable to quarantine any new plants whether purchased or received as a gift, before adding them to a greenhouse or a group of others indoors. Even though this may be inconvenient, I’d recommend isolating new specimens away from other plants for at least a month and to inspect thoroughly before placing them with others. How To Get Rid Of Mealybugs Once present, mealybugs can be difficult to eradicate. However, there are some ways to reduce their number and prevent re-infestation. That being said, it is sometimes easier to count one’s losses with a heavily infested plant and start again. Wash Them Away Perhaps the first control method to try is washing them off the plant. This can be done by using a hose spray adapter or a spray pump with water. Spraying the plant will hopefully dislodge the adults, any nymphs and their eggs, but can spread them elsewhere, so it is best performed outside one plant at a time. Predatory Insects Biological controls, including the use of predatory insects such as ladybirds and parasitic wasps, can be used effectively in enclosed spaces where mealybugs are present. The ladybirds can seek out and devour mealybugs and their eggs with surprising effect. “The genus of ladybird used for control is normally Cryptolaemus, so not the spotted ladybirds widely seen in the UK,” shares Peter. “It is worth mentioning that their larvae look alarmingly like mealybugs, so be careful if you’re spraying off mealybugs and using predators!” However, their use is limited to the warmer summer months where temperatures support their use. Insecticidal Soap Insecticidal soaps tend to be derived from plant oils or petroleum and act as a contact insecticide against mealybugs. Frequent application is often required for this process to prove effective, as the effect is short-lived. Plant invigorators are now available, which combine a mixture of natural pesticides to target the mealybugs and nutrients to stimulate plant growth which may have been reduced. Rubbing Alcohol Rubbing alcohol of 75% or isopropyl alcohol is another substance that can be used in the fight against mealybugs. To apply, soak one end of a cotton bud in the alcohol and use it to paint the insects and any eggs found on the plant, avoiding any unaffected foliage where possible. Allow your plant to dry for several hours and then wash off any dead mealybugs under water. Even though the alcohol is strong, it evaporates within minutes so the plant is not harmed. However, it is advisable to try this method on a small area first, before treating an entire collection. I would not personally recommend this method. Chemical Pesticide More persistent contact insecticides are available when other methods have failed. These can include sprays with cypermethrin, lambda-cyhalothrin and deltamethrin as the active ingredient and are authorised for use against mealybugs. Treatment For Commonly Affected Plants Cacti & Succulents Cacti and succulents are unfortunately often targeted by mealybugs. Introducing ladybirds as a biological control along with applying rubbing alcohol can prove effective, as well as changing their soil and washing their pots clean. Orchids Mealybugs can infest and damage orchids with surprising speed, leading to a lack of buds and their prized flowers. As with other houseplants, a strategy of using rubbing alcohol, plant oils and repotting can help treat and prevent mealybugs. Jade Plant The jade plant is a popular house plant grown here in the UK and is often affected by mealybugs. Jade plants can be very sensitive to fatty acids and plant oils, causing damage to the foliage and are thus not recommended for use against mealybugs. Instead, spraying the foliage with water and removing the insects by hand is the preferred option, with the targeted use of alcohol on a cotton bud a last resort. Hibiscus Unfortunately, all varieties of hibiscus whether grown indoors or outdoors can be targeted by mealybugs. For more tender varieties grown inside, a combination of introducing predatory insects and applying rubbing alcohol can prove successful. However, for hardier plants grown outdoors, plant oils or contact insecticides may need to be used, but not when the plant is in bloom. Ongoing Prevention Since mealybugs can be quite difficult to treat once established, prevention in the first place is most definitely the best line of defence. Even though quarantining any new plants is a hassle and not always easy if space is an issue, it is key in preventing any existing plant collections from succumbing to mealybugs. Regular plant checks are also an important part of preventing mealybugs as if identified, the plants can be isolated and treated, helping prevent contagion to the rest of the collection. Mealybugs are most attracted to new, soft green growth. In certain circumstances I would advise slightly reducing feeding and watering where possible, leading to a swifter hardening of new growth and better resistance to infestation. For certain houseplants, but only those that can handle it, lowering the nighttime temperature can also help prevent mealybugs, which prefer a warm and humid environment. References 1. Canna Research. (n.d.). Mealybugs – Pests & Diseases. Canna UK. Retrieved March 21, 2023, from https://www.canna-uk.com/mealybugs-pests-diseases 2. Mahr, S. (n.d.-e). Mealybugs. Wisconsin Horticulture. Retrieved March 21, 2023, from https://hort.extension.wisc.edu/articles/mealybugs-2/ 3. Mealybugs. (2021, April 28). Oklahoma State University. Retrieved March 21, 2023, from https://extension.okstate.edu/programs/digital-diagnostics/insects-and-arthropods/mealybugs/ 4. Johnson, P. (n.d.). Mealybugs on Orchids. American Orchid Society. Retrieved March 21, 2023, from https://www.aos.org/orchids/orchid-pests-diseases/mealybugs.aspx
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Bindweed Can Very Quickly Get Out Of Control - Why Weedkiller Is Not The Solution
IN THIS GUIDE What Is Bindweed? Why Is Bindweed A Problem? Why Weedkiller Is Not The Solution Manual Removal Preventing Spread Creating Competition & Ground Cover References Bindweed is a pernicious weed which many gardeners find a major problem. This is a weed which can very quickly get out of control, and unfortunately, in an organic garden, there are no quick and easy solutions. Organic growing does take a bit more work in certain circumstances, but it is always the best policy for those who care about wildlife, people and the planet. In this article, we will talk about bindweed, and help you understand how to keep it under control in an organic garden. What Is Bindweed? Bindweed is the name given to two problematic garden weeds. The first is ‘Hedge Bindweed’, also known as ‘Bellbind’ – Calystegia sepium. The second is ‘Field Bindweed’ – Convolvulus arvensis. Both of these plants are trumpet-flowered perennials, which can actually look rather attractive in the right setting. Bellbind is, as the name hedge bindweed suggests, a typical hedgerow plant. It climbs over and can smother hedgerow plants and even smaller trees. It has strong stems, heart-shaped leaves and large white trumpet-shaped flowers. Field bindweed resembles the above, but has weaker stems, and smaller flowers which are also trumpet-shaped and can be white or pink. These plants can be beneficial in a garden. The flowers provide pollen for bees and other pollinators and are a source of food for Lepidoptera species such as convolvulus hawk moths. Unfortunately, however, both can be a bane for gardeners, since they twine around other plants, smothering them and affecting their growth, or even killing them. So, while they may be welcome if not excessively growing in your garden, they are commonly a major issue where they grow more prolifically. Why Is Bindweed A Problem? Bindweed (of both types) is a problem because it can thrive in a range of settings, quickly taking over cultivated areas. Since these plants spread from the tiniest fragments of underground stem, which can penetrate extremely deeply (5m or more) into the ground, they can be extremely difficult to eradicate from growing areas. Established colonies can also spread out 2m or more in a single year of growth. Bellbind rarely produces seeds, but field bindweed produces seeds freely, and both can be viable for several years in the soil. Bindweed may not be an issue when it is within a wilder scheme, and where it is not adversely impacting the plant life around it. However, it can be a problem where it is growing particularly prolifically, or, of course, where it has made its way into cultivated beds and is impacting crops or prized ornamental plants. Why Weedkiller Is Not The Solution Topical application of weedkillers such as those containing glyphosate is effective against these weeds, but in an organic garden, weedkiller is not the solution. Keeping your garden organic and creating thriving, abundant, biodiverse and resilient ecosystems is always the best policy. Remember, non-selective weedkiller won’t just kill the weeds, but also any other plants with which it comes into contact. Since bindweed tangles around other plants, isolating the plants for chemical treatment can be challenging, especially with larger-scale colonies. Manual Removal While it is a large amount of work, manual removal of the above-ground portions of the plants, and ideally as much of the root system as possible, is really the only solution when it comes to containing bindweed or eradicating it from a particular bed or growing area. This can be achieved with a fork, working carefully over an area of soil and carefully removing as much of the root as you can. It is best to work quickly, soon after new growth appears in the spring, and then to keep your eyes open and repeat this procedure whenever new growth emerges. It is unlikely that you will entirely eradicate bindweed from a given area over just one season, but manual removal of this kind should keep it in check and prevent its further spread. If bindweed has infiltrated a bed with existing plants that you do not wish to disturb, then you should use a hoe to sever the tops off the plants at ground level. This is not a one-and-done job though, and you will need to repeat this process every 10-14 days through the whole of the growing season. This should weaken the plants and stop them from regenerating as effectively from their roots. Preventing Spread If you have been successful in eradicating bindweed from a garden bed or border through the cultural control mentioned above, you should note that new colonies can still establish from seed or root growth from adjacent areas or adjacent properties. New seedlings should of course be removed immediately from areas where they may become a problem. Wherever possible, it is also a good idea to consider installing a physical barrier 45cm deep into the soil along the edge of an area to prevent bindweed roots from creeping under a fence or other boundary. If bindweed is a persistent problem in kitchen garden beds, you might also consider creating bed edges which descend into the soil as well as rising above it to reduce the chances of bindweed making its way into those beds. Preventing spread also means being careful about the compost and other materials you bring onto your property, and the material in which plants you buy have been grown, as Master Horticulturist Colin Skelly shares: “This is how bindweed made its way into my garden – in a load of green waste compost. “It is in a densely grown bed of perennials with plenty of competition for light, nutrients and water, but it invariably finds a gap and begins to climb and smother other plants. “The only option is to locate the root source and try to take as much root up as possible, which is not easy as the white root breaks easily and will regrow to form new plants. “Determination and rigour will pay dividends but eradication is very difficult once it is established.” If you decide to tolerate areas of bindweed in certain parts of your organic garden for the sake of local wildlife, it is best to keep it contained, especially by making sure it does not set seed and become a bigger issue for other gardeners in your area. Creating Competition & Ground Cover Bindweed is a vigorous plant which can outcompete many others, but there are plants which can compete with it effectively. Where there is enough competition for nutrients and water, resources will be scarcer for the bindweed and it will not grow as prolifically if it grows at all. So, while it will not keep bindweed out of your garden altogether, keeping the soil well covered, with living roots of plants you want in the soil at all times, can help reduce the incidence of bindweed issues and other weed problems. Plant densely in perennial schemes, creating polycultures of plants which aid one another and work well as a holistic ecosystem. Layer plants in the space and make sure that there is good ground cover. A ground cover of chickweed, for example, has been used to suppress field bindweed in vineyards.1 A sequence of autumn and spring-sown green manure or cover crops in agricultural settings was also found to give good results against field bindweed. These give clues that can inform organic practice in domestic gardens too. Use living mulches of chickweed or other prolific low-growing plants between other plants in perennial planting schemes, or crop plants in a kitchen garden or vegetable beds. In areas of annual food cultivation, use green manures or cover crops to fill in any gaps in the planting throughout the year. These strategies might not keep bindweed out of your garden altogether, but they might play a role in making sure it does not get entirely out of hand. References 1. Chickweed : Board of Pesticides Control. (n.d.). Maine DACF. Retrieved March 9, 2023, from https://www.maine.gov/dacf/php/gotpests/weeds/chickweed.htm
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These Mistakes Might Cause Your Phormium Leaves To Turn Brown Or Yellow
IN THIS GUIDE 1) Overwatering 2) Nutrient Deficiencies 3) Restricted Roots 4) Leaf Spot 5) Frost Damage 6) Leaf-Yellow Disease References Phormiums are generally relatively easy plants to grow, whether grown in the ground or in containers. However, you may notice that the leaves are either turning brown or yellow, which is a common sign that the plants are not happy. There can be a number of common problems that lead to these issues. Some common problems that cause brown leaves are: Overwatering or waterlogged soil Nutrient deficiencies The phormium needs repotting Phormium leaf spot And yellow leaves may be caused by: Frost damage Leaf-yellow bacterial infection We explore these problems and what you can do about them below. 1) Overwatering Leaves turning brown can be a sign that the plant has received too much water. These are relatively drought-tolerant plants, but they cannot tolerate waterlogged soil. Make sure that water can drain away freely and take care not to water too much. Only water when the top few centimetres of the soil or growing medium is dry. 2) Nutrient Deficiencies Leaves turning brown around the edges can also be a sign that the phormium is not receiving enough nitrogen. Make sure that the soil is nutrient-rich and, if growing your phormium in a container, feed the plant with a seaweed feed or a compost tea to ensure that it gets the nutrients that it needs. 3) Restricted Roots The plant may also develop brown leaves as a sign of stress because it needs dividing or repotting. Simply repot into a bigger pot with sufficient compost for the plant. 4) Leaf Spot Unfortunately, brown leaves can also be a sign of a fungal infection, leaf spot, which is caused by a fungal pathogen. If this is the issue, the brown will be in patches on the leaves, and these may have a greyish hue or purplish edges. If you spot this issue, cut off the affected leaves as soon as possible to prevent the spread of this infection. 5) Frost Damage Yellow leaves can sometimes be caused by frost damage. These plants can cope with winter temperatures down to around -5-10°C in a sheltered spot, but they are not suitable for areas where there are long cold spells in winter. Leaves can also tear and tatter in strong winds, so a sheltered position is important, especially in areas where more extreme weather conditions might be expected. “Phormium makes fantastic coastal plants, but after a rough winter, they can look a little worse for wear,” shares Horticultural Consultant Colin Skelly. “You can prune out the worst of the torn leaves from the base but don’t exceed a third or you’ll hinder the ability of the plant to regenerate.” Phormium leaves that have been damaged by frost can discolour and become soft and mushy. Although the plant may wilt significantly and can even look dead, it will often come back if you care for it well. If your plant has been frost damaged, cut off the dead foliage with a sharp pair of gardening scissors or secateurs. Give it a feed, and give it some time, and new growth may well emerge. 6) Leaf-Yellow Disease Another problem that causes yellow leaves is leaf-yellow disease, which is caused by a bacterial pathogen called Phytoplasma.1 If infected, the plant can become stunted, and the bacteria can kill off the rhizome. The leaves will tend to turn yellow-orange in colour and will wilt until eventually, the plant will likely die. Remove infected plants carefully to prevent the spread of this problem in your garden. Though the issues above can arise, it is still the case that phormiums tend to be relatively low-maintenance and easy plants for UK gardens. They don’t usually have a range of issues and can be a good choice for busy gardeners. References 1. Marcone, C. (2011). Candidatus Phytoplasma asteris (yellow disease phytoplasmas). CABI Compendium. https://doi.org/10.1079/cabicompendium.7642
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Red Spider Mites Identification And Treatment: 'Prevention Is Easier Than The Cure'
IN THIS GUIDE What Are Spider Mites? Susceptible Plants How To Know If Your Plants Are Affected Treatment Measures 1) Non-Pesticidal Control Measures 2) Biological Control Measures 3) Pesticidal Control Measures References Red spider mites can be a real problem for gardeners. Even though they are tiny, they can multiply rapidly and do some considerable damage to plants, especially those grown undercover. However, having red spider mites on your plants isn’t necessarily the end of them, as there are some ways to help prevent them in the first place and control them if they are present. What Are Spider Mites? Tetranychus urticae, or the red spider mite as they are more commonly known, are a type of arachnid.1 Being less than 1mm in size, they are very hard to see and often can only be identified with the use of a magnifying glass, so it is very common to only realise that they are present after the damage has been done, or when there is a serious infestation. Red spider mites feed off the sap of plants and like warm, dry conditions. They are most commonly found in the greenhouse or on houseplants, or occasionally outdoors during the warmer months. Strangely enough, the red spider mite is not red all of the time. They actually start off either light green or yellow and only turn red in the autumn as the temperatures drop and the daylight hours diminish.2 Under magnification, two darker markings can be seen towards the head, giving them their other name – two-spotted spider mite. Susceptible Plants Red spider mites aren’t fussy when it comes to feeding. They like to feast on fruit, vegetables and ornamental plants, including tomatoes, peppers, cucumbers, strawberries, pelargoniums and poinsettias, amongst many others. Preferring a minimum temperature of 10-12°C, red spider mites usually appear in spring and adore warm and dry conditions, which is why indoor plants are so often targeted. However, if the temperature rises above 25°C, this is when they can really multiply, potentially doubling their population within only days. Due to their liking of a warm environment, red spider mites become less of a threat as the temperatures drop in autumn. However, if growing under artificial lights or in a heated greenhouse, they can be a constant and year-round threat. “With spider mites, prevention is certainly easier than cure, so good ventilation and watering can make all the difference in discouraging colonies from taking hold,” shares Horticulturist Consultant Dan Ori. “When buying or receiving new plants, give them a good check all over before you bring them into your home or garden. You may not spot a few mites, but you should be able to spot a pot riddled with them.” How To Know If Your Plants Are Affected Being so small, red spider mites are often hard to spot, especially due to the fact that they tend to feed and hide underneath the leaves. Often, the first sign of red spider mites being present is a pale mottling to the upper side of the foliage. Under the leaves, the young green or yellow mites can be seen, along with a shed of their white skin. As an infestation takes hold, silk webbing can be seen on the plant and the foliage can lose its green colour and drop prematurely, potentially leading to the demise of the plant. Treatment Measures With red spider mites, it is far easier to control a small number than a large infestation. Hence, it is wise to check any indoor or greenhouse plants from spring onwards as the temperatures begin to warm up. I’d recommend, when considering control methods, starting with the least potentially harmful option, before moving on to a pesticidal approach. Once even a small red spider mite infestation is present it can be difficult to bring under control, to the point where some gardeners count their losses and dispose of the infected plants immediately. However, there are some measures that can help prevent an infestation in the first place and control one if present. 1) Non-Pesticidal Control Measures Plants grown inside in hot, dry and overcrowded environments tend to be more prone to attracting red spider mites. This risk can be reduced by making sure there is adequate airflow around the plants and by increasing humidity. In a greenhouse, this can be achieved by damping down the floor, which will increase humidity levels and also reduce the temperatures, and opening the windows and doors to increase air circulation. With houseplants, a misting or spray bottle containing water can be used to increase humidity levels or you can move them to a more humid environment, such as a kitchen or bathroom. If possible, infested plants should be moved outdoors as soon as red spider mites are spotted. This will not only potentially help reduce the infestation and prevent it from spreading but hinder the red spider mites from overwintering inside a greenhouse or indoors. Cleaning out and disinfecting greenhouses at the end of the season is always recommended, but especially so with red spider mite present, as this will help prevent any pests from harbouring in nooks or crannies or under staging during the colder months. 2) Biological Control Measures If the cultural measures above do not reduce infestations to an acceptable level, then biological measures can be considered. Biological measures can include introducing predators to the affected plants. Biological measures do not work for every problem, but can prove very effective and have the added bonus of not being detrimental to the plants and not leaving harmful residues or damaging other living creatures. There are now a number of biological controls available online, which are approved for use against red spider mites and include the rove beetle (Atheta coriaria), a predatory midge (Feltiella acarisuga) and other predatory mites (Phytoseiulus persimilis).3 Biological controls can take time to work and so it is best to apply them as soon as red spider mites are spotted and before an infestation can take hold. Using predators usually requires certain temperatures and conditions for their application to prove most effective, so it is well worth adhering to their instructions to maximise their potential effect. Biological controls cannot be used at the same tide as pesticides, as the pesticides can interfere with the biological process. However, it is possible to use certain plant oils and fatty acids up until the conditions are right for a biological control application to be used effectively.4 3) Pesticidal Control Measures Pesticidal measures can include the use of organic sprays, plant invigorators, fumigants and insecticides. Organic sprays, such as those containing plant oils or fatty acids can be effective at controlling red spider mites. However, these measures often have a short window of action and may need to be reapplied frequently as per their instructions. Plant invigorators are not considered to be an organic method and combine both plant nutrients to stimulate growth, along with fatty acids to control red spider mites. Fumigants can also be used in greenhouses and glasshouses and can prove to be effective against red spider mites. Organic fumigants are now available and can be used with the plants left in situ, thankfully removing the tedious process of emptying all of the plants before application. As a last resort and when other control measures have failed, using a contact or systemic insecticide may be worth consideration. However, not all insecticides can be used safely on edible plants, so it is certainly worth checking before use, depending on what the red spider mites are feeding on. I would, however, not recommend using insecticides on plants that are in flower, to prevent any harm to pollinators. References 1. Tetranychus urticae. (2018, January 1). Science Direct. https://doi.org/10.1016/b978-0-12-802441-6.00014-0 2. Cranshaw, W., & Sclar, D. (2016, May 19). Spider Mites. Colorado State University. Retrieved March 23, 2023, from https://extension.colostate.edu/topic-areas/insects/spider-mites-5-507/ 3. Biological control of spider mites. (n.d.). Biobest. Retrieved March 23, 2023, from https://www.biobestgroup.com/en/biobest/pests-and-diseases/spider-mites-4967/ 4. Takeda, N., Takata, A., Arai, Y., Sasaya, K., Noyama, S., Wakisaka, S., Ghazy, N. A., Voigt, D., & Suzuki, T. (2020). A vegetable oil–based biopesticide with ovicidal activity against the two‐spotted spider mite, Tetranychus urticae Koch. Engineering in Life Sciences, 20(11), 525–534. https://doi.org/10.1002/elsc.202000042
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