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Bulbs are some of the most recognised plants in our gardens having been grown for many hundreds of years. Who can resist the first Daffodils as they herald the start of another year and brightly coloured Tulips that link spring to summer? The waxy flowers and exotic scent of summer Lilies and the bold spikes of Gladiolus make these perfect for the summer cutting garden as well as borders and containers.
‘Bulb’ tends to be a generic word used to cover bulbs, corms, rhizomes and tubers so let’s look at each one.
Bulb - made of modified leaves. If you were to cut a Daffodil bulb or an onion in half, you would see the layers of leaves and an embryonic flower bud in the centre. Examples of bulbs are Allium (onion family), Daffodils (Narcissus), Tulips and Lilies.
Corm - made from a swollen stem base. If you were to cut a Crocus corm in half you would see the swollen stem base in the middle of the bulb. This part contains the embryonic flower. Examples of corms are Crocus, Gladiolus and Anemone blanda.
Tuber - made from a fleshy, swollen underground stem (rhizome). Examples of tubers include Dahlias, some Begonias and potatoes.
Bulbs and corms can almost always be treated in the same way but tubers may need a bit more care when growing them.
Summer Flowering Bulbs
These flower in summer and early autumn and are on sale in your local garden centre from February onwards, for planting from late spring onwards. Tubers, such as Dahlias and Non Stop Begonias may have peat packed around them to help stop them drying out. Many summer flowering bulbs are not fully hardy in colder parts of the country and require ‘lifting’ in late autumn if they are to be kept for the following year.
Spring Flowering Bulbs
These flower from late winter to late spring, with a few Crocus and Colchicums flowering in autumn. They can be found in your local garden centre from the end of August onwards, for planting from September onwards. They are fully hardy and can be left in the garden from year to year.
Bulbs and Corms such as Crocus, Lilies, Gladiolus, Tulips and Daffodils can be planted directly into the ground, where they are to flower or into large containers to use on patios or place into borders to fill gaps with extra colour.
What will I need?
Trowel or border spade
Bone meal or another fast acting fertilizer
Garden line (if you want straight rows!)
Where shall I plant?
Most bulbs are best grown in a sunny site and well prepared soil that drains well to stop the bulbs rotting. However, Daffodils, Scilla and Anemone blanda also do well in part shade and can be planted under trees and shrubs for early colour.
Bulbs should be planted at three times their depth (click to download our handy guide below), so dig a deep hole and add some grit if your soil does not drain well. Add a handful of bone meal and mix it in. Gently push the bulbs into the soil so that they are firm. Make sure that they are the correct way up – you will be able to see dried roots at the base. The pointed end is usually the top of the bulb. It is difficult to tell with Anemone corms, but they will right themselves as long as they are not planted too deeply! Gently fill in the soil over the bulbs, making sure that you fill in around each bulb, without compacting the soil too much. Mark the area with a label and some coarse grit.
Once the bulbs begin to shoot through the soil surface, put more grit around them or use another method to control slugs, which may eat the new shoots.
As they grow away, taller varieties such as Gladioli and Lilies may require staking with bamboo canes to prevent the flower stems from snapping.
Remove the spent flower heads as they form to prevent the bulb from setting seed. This means that the plants energy will go back into the bulb for the following season.
Let the leaves die back naturally for at least six weeks after flowering before removing them completely.
In areas where bulbs are planted into grass for naturalising, the seed heads can be left on to increase the numbers and the grass left long until the leaves have died back completely.
Tubers such as Dahlias and Non Stop Begonias are best started off in a cold green house or on a sunny window sill. Tubers are more prone to rotting in cold, wet soil so if they are started inside, they will have a better chance to grow away more strongly once planted out.
What will I need?
Peat or multipurpose compost
Seed trays or shallow pots
Half fill a seed tray or shallow pot with compost or peat. Remove the tubers from the packet and place them on top of the soil. Cover with a thin layer of peat and add more as the shoots appear. Only water the tubers when the compost looks dry – overwatering can cause them to rot.
Once the tubers are shooting away, they can be planted out in to their flowering positions or into containers.
Guard young growth against slugs and snails – they are particularly fond of Dahlias!
Once the plants have established, feed once a week with a suitable liquid feed such as Notcutt’s Pour and Feed.
Tubers grown in containers will not need to be lifted through the winter – stop watering in late autumn and move the pot to a cold greenhouse until the following spring.
Tender bulbs and tubers should be lifted in the autumn once we have had the first frosts to blacken the leaves.
Prune off the leaves to reduce the height of the plants by half and lift them from the soil using a garden fork. Gently ease the plants up by digging down a forks depth – Dahlia tubers especially will be deeper than you think!
Label the plants with the variety and colour and store in a dry, frost free place through winter where they can continue to die back completely.
Planting in Containers
Many spring and summer bulbs are suitable for container planting. Use a good quality compost, such as John Innes No 2 and make sure that the container has plenty of drainage ‘crocks’ at the base to prevent the bulbs becoming too wet and rotting. Once the bulbs are growing away, feed each week with a liquid fertilizer and stake the flowering stems of taller varieties to prevent them snapping under the weight of the flowers.
In areas where squirrels are a problem, cover bulbs with wire netting until they have rooted, to prevent them being dug up. Remove the netting as the bulbs grow away to prevent the leaves being damaged. Mice and voles are also fond of bulbs, so keep an eye open for digging especially in containers and set traps for the offenders.