Gladiolus

Gladiolus: how do you recognise it?

Habit

Upright plant up to 1.2 m tall and barely 20 cm wide, with a stiff, unbranched flower stem.

Leaves

Stiff, narrow, sword-shaped leaves in a flat fan, fresh green to grey-green.

Flower

Large, funnel-shaped flowers on a long spike, all facing one way. They open from the bottom up, from July to September.

Colour

White, cream, yellow, orange, salmon, pink, red and purple, often bicoloured or with a blotch or edge in another colour.

Corm

A flat, round corm with a brown, fibrous tunic. Each year a new corm grows on top and the old one shrivels; small cormlets form at the base.

Flowering: July–September · Plants: April–June

Why grow it?

• One of the best cut flowers from your own garden: long, straight stems with a spike full of flowers.
• Plant a small batch every two weeks and you will have flowers from July into autumn.
• Bright colour in late summer, when the border starts to look tired.
• Bees visit the open flowers.
• Little work: plant in spring, water in dry spells and lift in October.
• Takes up little room: a row in the vegetable plot or a few gaps in the border will do.

Gladiolus: where does it grow best?

• Full sun: in shade the stems turn weak and it flowers poorly.
• Any well-drained soil: sand, loam or clay, neutral to chalky. In heavy clay, put a layer of sand under the corms.
• Normally moist soil; it must not dry out, especially while the spikes are forming.
• A spot sheltered from wind, or else canes or netting for support.
• Plant a corm every 10–15 cm, in groups in the border or in rows 30 cm apart in the cutting garden.

Light

Sun

Soil type

Sand, loam or clay

Acidity

Neutral or chalky

Moisture

Normal

Size

1.2 m tall, 0.2 m wide

Hardiness

Frost tender: lift the bulbs or tubers before the frost and store them frost-free

Goes well with

• Dahlia: The same routine, planting in spring and lifting in autumn, and together a generous cutting garden.
• Cosmos: Airy flowers and fine foliage beside the stiff spikes.
• Zinnia: Bright colours in the same sun, also good for cutting.
• Ornamental grasses: They hide the stiff, rather bare base of the gladioli in the border.

Gladiolus: when and how to plant it?

Plant in April–June.

1. Plant from April to June, once the soil has warmed up a little. A small batch every two weeks gives flowers until autumn.
2. Loosen the soil and mix in some compost; no fresh manure.
3. Set the corms pointed end up, 10–15 cm deep: the deeper they are, the better the stem stands.
4. Space them 10–15 cm apart.
5. Water in if the soil is dry.
6. For tall varieties, put in canes or stretch netting over the bed straight away, before the stems grow tall.

Care

Watering

In dry spells a good can of water once a week, especially once the flower spike is forming.

Feeding

Some organic fertiliser for flowering plants when the shoots are about 20 cm tall.

Earthing up

Draw some soil up around the base of the stems: they will stand up better.

Support

Tie tall spikes loosely to a cane or let them grow through netting.

Cutting

Cut the spike when the bottom one or two flowers show colour and leave at least four leaves on the plant, so the corm can recharge.

Tip: Cut gladioli in the morning, when the bottom flower has just opened: the rest of the buds will open by themselves in the vase. Every few days, remove the faded flowers at the bottom and trim a little off the stem.

Gladiolus: when to prune it?

When: No pruning is needed. Cut off faded spikes in summer and only remove the leaves in October, when you lift the corms.

How:

• Cut the faded spike just above the top leaf, so the plant does not set seed.
• Leave the leaves as long as they are green; they feed the new corm.
• When lifting, cut the stems back to 1–2 cm above the corm.

Caution: When cutting for the vase, always leave a few leaves on the plant, or the new corm stays small and flowers poorly next year.

Pruning calendar and basic rules

Propagation

Cormlets

When you lift the corms in October you will find small cormlets at the base. Store them dry and frost-free, plant them in a row in the vegetable plot in April and lift them again every autumn. After two to three years they are big enough to flower.

New corms

Each year one, sometimes two, new corms form on top of the old one. Break them apart after drying and plant them separately in spring.

Gladiolus: how does it get through the winter?

Hardy to 0 °C: protect in harsh winters.

• Not hardy: the corms cannot survive frost in the ground.
• Lift them in October, about six weeks after flowering or when the leaves turn yellow, and certainly before hard frost.
• Let them dry for two to three weeks in an airy, frost-free place. Snap off the old corm and the roots and store them in a paper bag or tray at 5–10 °C.
• Check the corms during winter and throw away any that are soft or mouldy.

Diseases and pests

• Thrips: Silvery streaks and flecks on leaves and flowers, and distorted blooms. The insects overwinter on the corms: lift in good time, store the corms cool and dry and do not plant affected ones.
• Corm rot: Brown, sunken patches on the corm, and plants that yellow and die. Throw away affected corms and do not plant in the same spot every year.
• Falling spikes: After rain or wind, heavy spikes flop over. Planting deeper, earthing up and staking all help.
• Slugs: They eat young shoots and flower buds. Pick them off in the evening or lay down a board for them to hide under.

Through the year

• February: Check stored corms; throw away any that are soft or mouldy.
• April: Plant the first batch of corms, 10–15 cm deep.
• May: Plant a new batch every two weeks. Watch out for slugs.
• June: Plant the last batch. Put in canes and earth up.
• July: First flowers. Cut when the bottom flowers show colour. Water in dry spells.
• August: Full flower. Remove faded spikes.
• September: Cut the last flowers.
• October: Lift the corms and let them dry in an airy, frost-free place.
• November: Remove the old corm and roots. Store at 5–10 °C.
• December: Rest. Keep the corms dry and frost-free.

Edible and useful

Not edible. All parts of gladiolus are poisonous, especially the corms: they can cause vomiting, drooling and diarrhoea, in children as well as in dogs, cats and horses. Gladioli that you lift in autumn, such as the large-flowered garden gladiolus and acidanthera, are stored frost-free until spring, often in the cellar or garage where the potatoes and onions are kept too: their flat corms with a brown papery skin can then be mistaken for shallots or onions. So store them separately, in a labelled box or bag, out of reach of children and pets. Do not leave corms lying where dogs could find them, and wear gloves when lifting, cleaning and planting them. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• The name comes from the Latin gladius, sword, after the shape of the leaves; it is also called sword lily.
• A gladiolus makes a brand-new corm on top of the old one every year, and the old one then shrivels. So what you lift in autumn is not the corm you planted in spring.
• Europe has wild gladioli too, such as the rare marsh gladiolus, but they are much smaller and more delicate than garden varieties.