How to look after summer-flowering bulbs in pots

Bulb experts from Holland share top tips for maintaining your summer pots through the hotter months and beyond...

Your summer-flowering bulbs should be well on the way to blooming now, bringing a riot of colour to the garden and adding fragrance and form to patio planting.

Lilies, dahlias, cannas and begonias can look amazing as stand-alone specimens in pots, while some can be successfully combined with other garden plants. Most summer bulbs are sun-lovers so are ideal for patio pots as they enjoy a good amount of heat in a sunny spot.

How to help them thrive throught the summer

A team of experts from The Joy Of Plants (thejoyofplants.co.uk), an initiative from The Flower Council of Holland, have come up with tips to look after some of its favourite bulbs: the Zantedeschia (calla), hybrid potted lilies and the star of Bethlehem (ornithogalum)...

Place in sun or shade

The temperature does need to remain above at least 5-8 degrees C, but that won’t pose a problem in the summer.

Don’t let the soil dry out

Water regularly, particularly when the plants are placed in pots or containers. The bulbs and tubers will survive through a slightly drier period, which is handy when you go on holiday for a week.

Feed them

Feed them once a fortnight to ensure lavish flowering.

What to do with them over winter

Bring summer-flowering potted bulbs indoors after flowering, in October or November, to give them a hibernation period whereby the plant remains dry and the foliage dies back. The bulbs and tubers will then produce plenty of new flowers during the next growing season. You can plant them outside again from April onwards to flower again in the summer.

How to look after different types of bulbs

Tuberous begonias

These like to be sheltered from wind, in partial shade, as the foliage can scorch in bright sunlight. They’ll also need to be fed regularly with a high-potash fertiliser and make sure you deadhead them as they fade, to keep the plant going.

If you want them to last through to the next season, store them in a frost-free place over winter. Once they’ve finished flowering, gradually stop watering them and they will die down. Cut stems down and lay the pots on their sides in a cool airy place, or take the tubers out and store them in dry compost until spring, when they should come back to life again.

Dahlias

Plant them in late spring outside in John Innes No. 3 compost in containers at least 30cm in diameter. Encourage bushy growth by pinching the tops out when the shoots reach 10-12cm and deadhead as they fade to encourage a long succession of flowers. Dahlias will be knocked back by the first frost, so once the top growth has gone, you can remove tubers from the pots, dry them and store them in a frost-free place until spring.

Lilies in pots

Again, planted in spring, many will be ready to flower in July and benefit from an occasional liquid feed with a high-potash fertiliser. Once blooms have faded, cut them off, but leave the stems and continue to water and feed to build up the bulbs’ strength for next year. The stems will die back naturally in late summer or autumn and the bulbs can be left in the same pots for a few years. After this time, replant them in fresh compost or in the border.