How To Grow Glorious Gladioli

Plant gladioli for glorious colour in the border or as a cut flower

Gladioli have been out of fashion for several years due to their reputation as being blousy and vulgar, but they are now starting to make a comeback as their true potential is being realised. They make an excellent long-lasting cut flower, can add height and inject a shot of colour into the herbaceous border and the smaller species types are restrained and dainty. They are a genus of half-hardy perennial bulbous flowering plants, being part of the lily family, sometimes called the Sword Lily. They originate mainly from South Africa, which has approximately 250 of the 260 known species. The remaining 10 species come from tropical Africa, Asia and areas around the Mediterranean. In the wild in South Africa they are pollinated by sunbirds, bees and moths. In the UK they are an important food source for many moth and butterfly species including the Large Yellow Underwing. They are often associated with a 40th wedding anniversary. They range in size from 20cm (8”) to 180cm (6’) and come in every colour from the pure white of ‘White Prosperity’ to the darkest chocolate/ burgundy of ‘Espresso’; with frilly petals, bi-colours or picottee edged. There is a colour to match any garden scheme.

Most of the varieties on sale in garden centres are the result of years of hybridisation but you can find the small dainty magenta Gladiolus communis ssp. byzantinus and the shorter Nanus varieties. One variety grown in a pot makes a good filler in the herbaceous border injecting a shot of colour and height, once they have gone over just lift and replace with another fresher pot. Grown for a cut flower they can be grown in rows along the edge of the vegetable plot as they do not take up very much space. When buying corms make sure they are firm and without any mould.

Position

They need a sunny, sheltered site with well-drained, moisture retentive free draining soil. If you have sandy free draining soil then incorporate some organic matter in the form of good quality peat-free compost, home-made garden compost or well-rotted farmyard manure. If you have heavy clay soil incorporate horticultural grit or compost with a large texture to improve the drainage. They need plenty of water but will rot if they are left sitting in wet soil.

Planting

Wait until the soil has warmed up in March/April and plant about 15cm (6”) deep and 15cm (6”) apart. If they are for cut flowers stagger the plantings, a week apart from March to May should give you a continuous supply of cut flowers throughout the summer. Plant in pots in a good quality peat-free compost if they are to be sunk into the herbaceous border. Plant all at once if you want a glorious burst of colour. Corms planted in February/March should flower in mid-June and planted in May should flower in late September.

Aftercare

As soon as the flower spike appears tie each flower to a cane with soft garden twine. When they start to flower, feed fortnightly with a high potash fertilizer such as Tomorite or home-made comfrey juice, keep this up through the flowering season and for 3 weeks after the flower spike has died back, this will feed the corm for next year. Make sure they are kept well watered throughout the summer.

Storing for next year

Once the foliage has died back lift and put somewhere to dry out. Once they are fully dry break off the stems and separate the corms, discarding the main corm if it is shrunken. Dust with a sulphur powder to deter any pests and disease. The small corms may take several years to bulk up enough to produce a decent flower spike. If they produce a small weak flower spike the following year just cut it off so the plant puts all its energy into building a good corm. Keep the corms dry and frost free over the winter. If you live in an area which has mild frost free winters you may get away with leaving them in the ground and just mulching.

Pests and diseases

They are usually pest and disease free.

Yellowing leaves and stunted growth could be a sign of a virus, in which case they will have to dug up and destroyed, either on the bonfire or in the grey waste bin. Don’t put them on the compost heap as this will only incubate the virus which could spread to other plants when you use the compost.

Yellow streaks on the leaves and distorted flowers can be a sign that the corm has been attacked by thrips when it has been stored over winter. When storing dust with sulphur powder.

Recommended varieties:

The Nanus varieties are slightly hardier than the large flower hybrids, and if left in the ground will spread to form a large clump.
Nanus ‘Nymph’  -  white with magenta markings
Ramosus ‘Robinetta’  -  red with a cream stripe
Colvillii ‘The Bride’  -  white with a yellow/green veins
Gladiolus communis ssp. byzantinus  -  magenta, small and dainty
Espresso  -  chocolate/burgundy
Zorro  -  wine red
Green Star  -  lime