Summer-flowering bulbs add a punch of colour to your garden from late spring right the way into autumn. They are often tall, showy plants that have rich colours and make great cut flowers.
Summer bulbs illuminate borders and create wonderful container garden displays. And like all bulbs, they are also very easy to grow. Simply put them in the ground and leave them to it!
Technically, many of the plants listed below grow from corms or tubers, not bulbs. The main difference is that bulbs are fleshy and have different layers, like onions. Corms and tubers are solid and the same all the way through.
Here are my top tips for planting summer bulbs, tubers and corms. It includes lilies, irises, dahlias, gladioli and begonias.
How to grow lilies
Exotic lilies add something special to the garden and thrive in pots and borders. They need a sunny spot and rich soil that doesn’t get waterlogged. Plant the bulbs as soon as you buy them because they die if they become dehydrated.
Lily bulbs need planting very deeply, up to three times the height of the bulb itself. If you want to grow them in pots, choose tall, deep containers and plant closer together than normal.
The best flower displays come when the plant’s stem and flowers grow in full sun, but the bulbs are kept cool and shaded. Plant them deeply and add a mulch, or grow ground-cover plants around them.
Lilies are hungry plants and will need regular feeding. Add a high-potassium fertiliser like tomato feed every two weeks. Continue feeding after they have finished flowering to swell the bulbs for next year’s display.
Stake tall lilies to stop the stems snapping in the wind. Tie them to garden canes with soft twine and loosen the ties when needed.
Deadhead blooms as they fade to prevent the plant from setting seed. Remove the flower at its base where it joins the stem.
How to grow irises
The iris family has a huge range of colours, shapes and growing habits. Some plants love damp soil and will even grow in water margins. Some thrive in borders and others are happiest in dry, sunny spots.
Always check that the plants you are buying will suit the position you want to grow them in.
Plant irises in spring once the frosts have finished. Irises are technically rhizomes, which is a clump of fleshy root. This means they should be planted near the soil surface, rather than deep underground like traditional bulbs.
Place the rhizomes of sun-loving varieties just on the surface and cover the little roots with a soil. Position the crowns of moisture-lovers just below the ground.
Irises do not like to be crowded, so follow the spacing directions on the packet and avoid surrounding them with dense planting.
Snip off dead flower heads with secateurs and remove the entire flower stem once the display is over.
Irises need to be left exposed to sunlight after flowering – this is how they develop flowers for the following year. Leave them in situ and either remove the leaves when they wilt or leave in place for frost protection.
How to grow dahlias
Dahlias are highly productive plants that make great cut flowers. They like any rich soil with good drainage, so dig plenty of compost into the planting hole. You can also add a layer of grit on heavy soils to aid drainage.
Dahlias are frost-tender plants so don’t plant them into the garden until all risk of frost has passed. Most people start dahlias off in pots indoors. Plant them up in March or early April in pots of general purpose compost.
Place the pots in a brightly lit spot and keep the soil moist. Plant outside when the frosts have passed and the plants have become a bit bushy.
Alternatively, you can plant dahlias directly in the ground. This is less work, but bear in mind that they will flower a little later and you will need to watch for frosts. Cover with cloches or fleece to protect the foliage on frosty nights.
You can also plant dahlias in containers. Use large, deep pots and general purpose compost. Add a slow-release fertiliser and plant as normal.
Plant the dahlias in a deep hole and water well. After a couple of weeks, add a scattering of fish, blood and bone meal. Then begin adding general purpose fertiliser to the watering every two weeks. Water heavily in dry periods.
Pinch out the growing tips back to a pair of leaves once the plants are around 40cm high. This makes the plant bushy and encourages vigorous flowering.
If you want large flowers, remove all but three to five flowering stems. It seems brutal but it will work. For smaller flowers, keep seven to ten flowering stems. You can also remove smaller flowering buds on the stem to make the plant focus on the primary bud.
How to grow gladioli
Gladioli are coming back into fashion as of late. New varieties have appeared with smaller or pastel-toned flowers that fit better with our gardens.
Gladioli corms prefer light, sandy soils in full sun. You can add plenty of coarse grit if you have heavy soil, and line the bottom of the planting hole with a layer of grit too. You can also enrich the soil with a low-nitrogen fertiliser, but make sure it is well mixed in or it could burn the corms.
Plant the corms deeply (10-15cm) and leave plenty of space between them. Plant even more deeply on loose, sandy soils to stop plants being uprooted by the wind.
Keep well-watered, especially once the foliage appears. Apply a layer of mulch around plants in dry weather. Unless they are supported by surrounding plants, tall gladioli varieties will need staking.
If you are growing gladioli for cutting, plant a few corms every couple of weeks for a continuous supply. Cut the stems when the bottom flower bud is opening and the rest of the buds are showing colour.
How to grow begonias
Begonias are rich, colourful plants that are perfect for pots and hanging baskets. They are happy in sun or partial shade in moist, well-drained soil.
Plant begonias in containers filled with general purpose compost. They should be planted with the indentation on the top – this is where the tuber will sprout. Nestle the tubers just onto the surface without covering them with soil.
Alternatively, plant begonias in borders by loosening the soil with a fork and nestling the tuber into place as above. Water well and keep the soil slightly damp but not soggy.
Begonia tubers are tender and should not be planted until the frosts have passed. You can always start the tubers off indoors in pots. Follow the planting instructions above and keep in a warm, brightly lit spot.
When the weather has warmed up, harden off the plants by moving them outside during the day and bringing them back in at night for a week or so. Then plant the tubers outside.
Feed the plants every two weeks with high-potassium fertiliser like tomato feed. Water well during dry weather but try not to soak the leaves.
How to lift and store summer bulbs
Many summer bulbs, including dahlias, gladioli and begonias, are damaged by frost and should be stored indoors over winter.
Wait until all the leaves have died down at the end of summer. Lift the bulbs out of the soil with a garden fork, taking care not to damage them.
Remove any dead or dying leaves and cut back the leaves or stems to within one inch of the bulb. Leave the bulbs out in the sun to dry out. Then brush all the soil off them.
Store the bulbs in mesh bags in the shed or garage. They need air circulation to stop rot setting in. Keep checking the bulbs and remove any that start to rot. Replant them again in spring.