How to grow gladioli

We could all do with growing more gladioli, because these upright flowers light up a border. They’re great for cutting and you can plant the corms in succession, a handful a few weeks apart, and fill awkward gaps left by oriental poppies, for instance, because the showier hybrids are able to produce flowers within weeks. Some are far better in pots, some will happily overwinter in most gardens and others are best treated rather like dahlias. They can be grown in groups and, although they were considered bad taste for many a year, gladioli are definitely on the rise.

When to plant gladioli bulbs

Gladioli are usually planted  in spring (March or April) but guard against planting showy, frost-tender gladioli varieties too early. Mid-May is perfect.

If your garden’s wet, put a layer of coarse grit in the bottom of the hole to improve drainage. Plant them to a depth of six inches if possible (15cm).

You can succession plant corms every two to three weeks, up until the end of June.

Pay a little more for bigger bulbs.

Do you need to stake gladioli?

Outdoor gladioli always need staking and the best method is to plant the corms and place the stakes by or round the corms before you cover the corms up. Use cane toppers and there are some attractive options, or wine corks.

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After flowering

Once the flowers have faded, remove the stems.

Should you lift gladioli?

Hardiness varies greatly, because gladioli are found growing naturally in South Africa, tropical Africa, the Mediterranean and Europe. One reddish purple species, Gladiolus illyricus, is native to the New Forest in Hampshire. It’s found on roughly forty sites, but it’s right on the edge of its range. There are 260 South African species and they flower best when they get moisture during their growing season. Some species have been used to breed showy garden forms, so generally you will need water garden your gladioli in dry summers. The Mediterranean species are hardier generally, but if it’s big and showy it’s likely to be tender in most areas of the UK.

Overwintering gladioli in the ground

Whether you lift your gladioli or not will depend on where your garden is. Sarah Raven, who gardens at Perch Hill in East Sussex, grows and sells a lot. She is able to leave her gladioli in the ground, as long as she mulches them with a three-inch layer of garden compost in late autumn. However, if your garden is very wet, very cold or both you could run the risk of losing them over winter. Rather like dahlia tubers, the decision is yours.

Overwintering gladioli in pots

Stop watering when the leaves turn yellow in late autumn and cut the foliage down to about 10cm (4in). You can either keep them in the pot, or dig the corms out of the compost and place them in trays somewhere cool, frost-free and dry. If you have a mesh bag hang the corms up to allow air to circulate round them. If you’re buying new ones, order early them early in the year.

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Starting gladioli corms off in pots

Pots can be planted in March or April and it’s often better to stick to one or two varieties.

Use a good quality peat-free compost and good-sized pots that are at least fifteen inches across. (40cm)

Stake as you plant the corms and do use cane toppers.

Keep the pots in a cold, bright place that’s frost free, and bright.

Water them little and often to start with and then move them outside in late May, into a sheltered position in full sun.

When the flower spike emerges, feed them every couple of weeks with a liquid tomato fertiliser.

Make sure you continue to water your pots of gladioli throughout the growing season, as they will dry out more quickly than those in the ground. Stop watering when the leaves yellow, then lift and store.

Good gladioli varieties for growing in a pot

‘Glamourglad Waris’ - from Parkers
A shorter, daintier gladioli with grape-purple flowers finely edged petals and centres in white. Very upright and pristine. 60cm/ 2ft

‘Vulcano’
A new form of the shorter and more delicate G. nanus with deep-pink flowers shaded in white. The lower petal has a purple blotch. 35cm/ 1ft.

‘Verax’
This butterfly variety that produces white flowers with lilac-purple throats. Flowers July to September. 60-80cm / 2ft or slightly more.

'The Bride'
Pretty, delicate white gladioli with ethereal flowers in May. A florist’s favourite. 50cm / 18in.

‘Nymph’
Exquisite white flowers delicately ‘diamoned’ in vivid-pink as if someone had drawn on the petals. 50cm/ 18in.

G. papilio 'Ruby'
Velvet-textured crimson flowers on tall arching stems and far more subtle in form because the smaller flowers are almost bell-shaped. Hardy enough to grow outside, as it did at Hadpsen House in Somerset, but it flowers better in a pot. Avon Bulbs has a deep-purple seedling aptly named ‘Thunder’. 90cm/ 36 in

Gladioli varieties that do better in the ground

Gladiolus communis subsp. Byzantinus
This magenta-flowered Mediterranean species, which performs in May or June, grows in olive groves in the wild. It’s hardy and can be left in the ground in well-drained, sheltered positions. It’s colonised parts of Cornwall and the Scilly Isles and it’s known as 'Whistling Jack'. It often graces show garden at the Chelsea Flower Show, because it’s reliable. The subsp. byzantinus bit of the name is a must, because ordinary G. byzantinus can have dull-pink flowers.

'Belle de Nuit'
Velvety, rich purple-black with large flowers. A dramatic addition with oranges or bright pinks and also good with silvery foliage. 100cm/3ft.

‘Black Velvet’
Huge velvety blooms in deep purple. 100cm/3ft.

‘Plum Tart’
Silky flowers in a warm cherry-red. 100cm/3ft.

‘Velvet Eyes’
An orchid-like arrangement of purple, grey and cherry-red and this one fades to denim-blue shades. 90cm/3ft.

‘Evergreen’
'Evergreen' is the brightest budgerigar-green with a dense spike of open flowers. Good with sultry shades. 90cm/3ft.

‘Green Star’
Ruffled lime-green flowers that soften to lime-yellow as they age. A lot of flower all at once. 120cm/4ft.

‘Sapporo’
A Neapolitan combination of peach, lime green and raspberry. A little anaemic for garden use, but great to cut. 120cm/ 4ft.

'Tarantella’
A frilly apple-white and green, for a cool position in semi-shape. 110cm/43in.

‘Purple Flora’
The best purple gladioli, from the moment the grass-green buds split. Each purple petal is faintly lined in white. 120cm/4ft.

‘Flevo Laguna’
Acid-green flowers flushed with faded purple, have made this elegant gladiolus highly popular with flower ladies and gardeners alike. 60cm/ 2ft or more.

Buying your gladioli

Pay a little more for bigger bulbs, and go for single varieties, rather than mixtures. Suppliers include Sarah Raven, Peter Nyssen, Parkers and Pheasant Acre.

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