BULBS

What Are Bulbs?

When we talk about bulbs in horticulture, we are commonly talking about plants that grow from bulbs below the soil. Botanically speaking, a bulb is a part of a plant that functions as a food storage organ during the period of dormancy. The leaf bases on a bulb are also sometimes known as scales. Roots emerge from a basal plate on the underside of the bulb, and new above-ground growth emerges later from the top side.

A number of common and familiar garden plants belong to this category. Common bulbs can flower throughout much of the year, but perhaps most gardeners are most familiar with the spring-flowering bulbs – such as daffodils and tulips, for example. Spring flowering bulbs are sometimes described as spring ephemerals – they flower over a relatively brief period before the foliage and flowers die back down and the nutrients etc. returned into the bulb where they are stored until the following year.

Bulbs cycle through various stages of growth. First, during the vegetative stage, the bulb grows to maturity – reaching flowering size. When the plant reaches flowering size, it will enter the next phase – which is all about reproduction. The plant will flower, perpetuating the life cycle.

Environmental conditions are needed to precipitate the change from one stage of growth to the next. For some bulbs, a change in temperature is key. With spring bulbs, for example, the shift from chilly winter temperatures to spring warming triggers their progression.

After spring flowering bulbs have finished flowering, there is another stage, known as the foliage period. During this period the plant captures energy and nutrients, and as the foliage dies back, these are stored up in the bulb for next year’s growth cycle.

In gardening, we will often divide bulbs (referring to those cultivated for their flowers) according to the time of year when they are in flower.

You will find:

  • Late winter and spring-flowering bulbs.
  • Summer flowering bulbs
  • Autumn flowering bulbs

There are bulbs for naturalising in lawns and elsewhere in the garden, and bulbs to grow in containers.

Popular Bulbs Grown In The UK

Popular bulbs grown in the UK include members of the allium family grown in the vegetable garden. But commonly, bulbs are flowering plants prized for their blooms. Here are some of the best known and best-loved flowering bulbs grown in Britain:

When And How To Plant Bulbs

Bulbs are planted in autumn, spring and summer. When bulbs are planted, of course, depends on when in the year they flower. `Spring flowering bulbs are usually planted in the autumn, as are hardy summer-flowering varieties.

When exactly you should plant spring or summer flowering bulbs depends on which specific bulbs you are planting. Ideally, those that bloom early in spring (crocus, daffodils or hyacinth for example) should be sown before the end of September. Hardy summer flowering bulbs should be planted out in September too. Though for both of these categories it is not usually too late to do so in October if you do not quite get round to it that month. Tulips, however, which bloom a little later than the spring-flowering bulbs mentioned above, should not be planted out until November.

Other summer flowering bulbs and autumn flowering bulbs are sown in spring or early summer. Some spring-flowering bulbs are best planted after flowering, but whilst still in leaf.

Planting bulbs the right way up usually means a much better chance of success. The roots should of course be at the bottom, and shoots at the top. With some bulbs, the basal plate is easy to see, and sometimes, the bulb is pointier at the top. But with others, it is not so clear. If you can’t tell which way is up, it is best to plant the bulb on its side. It should still grow fine.

It is also important, when planting your bulbs, to make sure there are no large clods or stones that will get in the way as shoots try to emerge. And should also ensure that there is good contact all around between the bulb and the soil/ growing medium, without any air pockets.

If you want to create naturalistic planting that looks as though the bulbs have naturally emerged, one trick is to drop the bulbs from waist height. Let them fall as they may, then resist the urge to space them more artistically and plant each one exactly where it has fallen. If you have a lot of bulbs to plant, a bulb planter is a tool that may come in handy.

Bulbs can of course be grown in containers as well as in the ground. But make sure that the container and potting medium that you have chosen are appropriate for the plant or plants you are growing.

Water when you plant your bulbs, and consistently over time. Remember that when growing in containers, plants will generally need to be watered more often.

What Conditions Do They Prefer?

crocus plants covered in snow during winter

There are a wide range of different bulbs, and the conditions that they prefer can differ widely. For example, daffodils and tulips both prefer a sunnier and more free-draining setting. Some plants like crocus and bluebells will flourish in dry shade. Some bulbs, of course, are tender and best grown in containers. Some bulbs have to be lifted for storage over the winter months, and may rot if left in place.

When choosing which bulbs are right for your garden, it is not just a good idea to think about the needs of the individual types you are considering and the conditions where you live. It is also a good idea to think about the impact bulbs can have on the garden scheme as a whole.

Certain bulbs can look best when planted in naturalistic drifts in lawns or a bed or border. When it comes to options like daffodils and tulips, it is often the case that the more plants you have together, the better they will look and the more effective the scheme will be.

What Conditions Should You Avoid?

Whichever bulbs you are growing, and whether you are growing them in containers or in the ground, water is important. All bulbs require adequate water while they are in growth, and for the foliage period of six weeks post-flowering. The soil or growing medium around the bulbs should feel moist, but not be wet to the touch.

Many bulbs, when sown naturalistically in the soil, will not require fertilization. A good quality organic mulch should be sufficient to provide the nutrients they need. However, many bulbs planted in containers may suffer from a lack of potassium during the flowering period. You should consider feeding bulbs in containers with a high potassium organic liquid plant feed from early spring through to six weeks after flowering.

Avoid removing or cutting back dead foliage until at least six weeks after flowering, or the bulbs may not have the nutrients they require to flower the following year. If the bulbs are to be lifted for winter storage, this should also be done only after this six week period has elapsed.

Frequently Asked Questions

How Deep Should You Plant Bulbs?

Generally speaking, spring bulbs should be planted around 2-3 times their own depth. Though this is just a general rule of thumb and guidelines for individual types may differ.

How Should You Store Them?

If you are lifting bulbs, and not simply leaving them in place in the garden over the dormant season, then remember to wait to do so until the foliage period has elapsed and the foliage has entirely died down.

Next, carefully lift the bulbs and clean them. Trim back the roots and remove any outer, flaking layers. Make sure you check the bulbs over carefully and only keep and store bulbs that are healthy and in good condition.

Put the bulbs on a flat surface at home and leave them out to dry for a day or so. This can help in preventing fungal rots from taking hold while the bulbs are in storage.

You should store bulbs in paper bags, or nets, that allow for sufficient airflow. These should then be placed for storage in a dry and cool location. Labelling them can help you identify them in future.

Which Way Up Should You Plant Your Bulbs?

Bulbs should be planted with the basal plate (from which roots form) at the base. If the basal plate is not obvious then you may be able to identify it as a slightly rougher area. Some bulbs will have a more pointed end or tip, which will go upwards. Though this is not always easy to identify with some bulb types.

If you cannot identify the basal plate or growing tip, plant the bulb on its side. And do not worry too much. Even if you get in wrong, many bulbs will still manage to find their way to grow up and out of the ground towards the sun.

How Does A Bulb Planter Work?

A bulb planter is a tool that can be used to make it easier if you are planting a large number of bulbs in your garden. Though they are not strictly necessary, they can make it much quicker to achieve the same results. There are several different types of bulb planter. The simplest are handheld manual tools. Usually, these have depth measurements to help you plant bulbs at the right depth, and can be used to core out plugs of soil to the right depth for the bulbs you are planting.

Some bulb planters require you to stoop or kneel down, and manually force the tool into the ground. Some also have a plunger that allows you to release the plug of soil into the hole once you have planted the bulb.

Others have full-length shafts that allow you to stand to make things easier on your back and knees. A foot rest on these models will usually allow you to easily press the tool into the soil. These can also often have a mechanism that releases the plug of soil back into the hole after planting.

There are also drill powered bulb planters. These bulb planters require electricity hook up, or battery power. They attach to a standard drill and core out holes, usually to around a 2-inch diameter, that can be up to around 9 inches deep. These powered bulb planters could be a good option where manual hole digging will be too challenging or time consuming for the gardener. Though with this type, the soil will have to be replaced manually above each bulb.

What Should You Do With Bulbs In Pots After Flowering?

After bulbs in pots have flowered, you can deadhead the flowering stalks – cut them right back to the base, This will stop the plant from expending energy on seed production when this is not required for propagation. Energy is therefore conserved for next year’s flowering.

However, the foliage should not be removed. You should not cut back foliage for at least six weeks after the flowering period is at an end. Ideally, you should only remove foliage once it is dry and straw-like, once the nutrients have had the chance to be stored in the bulb. Do not tie or knot the leaves and continue to water and feed your plants over at least this six week period.

When Is The Latest You Can Plant Bulbs?

While, as mentioned above, bulbs for spring flowering are usually planted in the early to mid-autumn, you can continue to plant many bulbs until the ground is frozen. Often, you will still be able to plant spring-flowering bulbs after the first frost where you live. Bulbs will perform best in spring if they have a month or so to establish themselves before a hard freeze, but there is some flexibility and planting them a little late can often be better than not doing so at all.

Most bulbs that flower in spring require a chilling period of 12-15 weeks. They must experience temperatures between 1 and 7 degrees C. during this time. The time from the end of this chilling period to the reproductive flowering phase varies by species. As long as the proper chilling has occurred (either naturally or by artificial means) flowers will usually form in 2-3 weeks.

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