How to store summer-flowering bulbs over winter

Winter may seem a long way off, especially as the weather remains relatively warm for the time of year, with late-blooming favourites such as dahlias still in flower.

But you’ll need to be ready to lift summer-flowering bulbs, tubers, rhizomes and corms including dahlias and cannas once the cooler weather hits.

The most popular summer-flowering bulbs, some of which are still flowering now, need to be lifted after the first proper frost when their leaves have blackened, perhaps around early November depending on the weather, says Ian Clark, marketing manager for Taylors Bulbs.“Alternatively you can lay a good mulch on top rather than taking them out completely. That’s what I do with mine. I’d just use clippings from other plants, but you can buy a proper mulch at garden centres.“It’s also geographical. In the south you’re going to get away with leaving the tubers in more so than further north, just because of the winter temperatures.”

“If you’ve got bark to use as a mulch, that’s great as it’s probably going to give you more thermal protection,” says David Turner, marketing manager for seed and plant supplier Fothergill’s.Gladioli

There are numerous types of gladioli – the tall, showy, large-flowering ones which aren’t hardy and the dwarf, more compact perennials, Gladiolus nanus.“They are smaller, wilder looking types. Common ones include ‘Las Vegas’, ‘Carine’ and ‘Mirella’ and these dwarf types tend to be shorter, say 60-80cm, whereas a common gladioli would be around 110cm tall,” says Clark.You might grow dwarf varieties in a herbaceous border with other hardy perennials, but the taller gladioli won’t survive the winter so you’ll need to lift them and store them as you would dahlias, replanting them next May or June, once the risk of frost has passed, he advises.Cannas

These tropical-looking plants are often placed as a centrepiece of large pots and if you move the pots to a south-facing brick wall, in a sheltered spot out of winter wet and frost, they may survive winter, says Turner, although you may have to give them extra insulation with horticultural fleece during the coldest spells.“You are protecting them in quite a small space in a container. In general terms it’s easier to keep that amount of soil warmer,” he says, adding that pots can also be moved either indoors or into a potting shed where there is still light.

Taylors Bulbs advises gardeners to lift canna rhizomes when frost blackens the foliage as they are not frost-hardy, and to store in a frost-free place until planting time in late spring.

“You can divide them to make new plants just by chopping through them with a knife or a spade, to position in different places,” says Clark.

“If you have a greenhouse you can pot them up in a three-litre pot to get them started in spring and plant them out after risk of frost has passed. Shorter ones like ‘Louis Cottin’ are good for pots.”Avoid rubbing the rhizomes too hard because you can damage the skin, says Turner.“Whilst you want to get as much of the soil off as possible, treat them a bit more delicately than others.”Begonias

Begonia tubers – the solid, swollen, rounded underground stems that store food and energy – will need protecting from freezing temperatures if they are to return in subsequent years.“Lift them after they’ve finished flowering and before the first frost, and snap the stem off. It will just separate from the tuber,” says Clark.“Begonias are great to start off in pots in a frost-free greenhouse before you plant them out into the garden to get a head start,” he explains. “Then plant them out once all risk of frost has passed.”

“If possible, when you’re working with a fork to loosen the soil, try to lift the thing as a whole,” says TurnerLilies

The easiest of the summer bulbs (unless you have an invasion of lily beetle) are lilies, which don’t need lifting and should come back year after year.How to store bulbs“You need to store bulbs in a cool, dry, dark, frost-free place and in an ideal world you’d store them in trays that have air holes in, so you have circulating air,” says Turner.Shake the soil off them before storing and make sure none show signs of mould.“I would avoid using cardboard because if there’s moisture in the air the cardboard with absorb it and you want to keep them as dry as possible. People use paper bags to keep them in with the tops open, or just use stacking trays with vents,” says Turner.

Some surface mould may appear over the winter, but you can gently brush that off, Clark suggests.“A bit of surface mould can be brushed off but you don’t want them starting to rot. Also, if you leave them in the ground and they freeze, the tubers will go black and mushy.”