Common cornflag

Common cornflag: how do you recognise it?

Habit

Upright plant, 60–70 cm tall, with narrow fans of sword-shaped leaves.

Leaves

Narrow and sword-shaped, fresh green; die back after flowering.

Flower

A spike of ten or more flowers in one row, all facing one way, in June and July.

Colour

Magenta-pink with paler streaks on the lower petals; there is also a white form.

Corm

Small, flat corm with a fibrous skin; each year a new corm forms on top of the old one, surrounded by cormlets.

Flowering: June–July · Plants: March–April and September–October

Why grow it?

• A gladiolus that is hardy: no need to lift the corms every year.
• A vivid magenta-pink in early summer, among the perennials.
• Graceful, airy spikes that suit a naturalistic border or gravel garden.
• A lovely cut flower; cut the spikes when the lowest flower opens.
• Bees visit the flowers.

Common cornflag: where does it grow best?

• Full sun, in a warm spot.
• Well-drained soil: sand, loam or clay, neutral to chalky. Improve heavy clay with coarse sand.
• Dry to moist; in wet winters the corms rot.
• Plant in small groups among perennials, about 10 cm apart.

Light

Sun

Soil type

Sand, loam or clay

Acidity

Neutral or chalky

Moisture

Dry or normal

Size

0.7 m tall, 0.15 m wide

Hardiness

Hardy (to -15 °C)

Goes well with

• Catmint: Lavender-blue flowers at its feet, also for sun and dry soil.
• Lavender: The same sunny, dry spot; flowers at the same time.
• Ornamental onion: Purple globes in June next to the magenta spikes.
• Ornamental grasses: Fine stems between which the pink spikes stand out well.

Common cornflag: when and how to plant it?

Plant in March–April and September–October.

1. Plant in September–October or in March–April.
2. Loosen the soil and, in heavy ground, mix in some coarse sand.
3. Plant the corms 10 cm deep, flat side down and pointed end up.
4. Space them 10 cm apart, in groups of ten or more.
5. Water after spring planting; in autumn this is usually not needed.

Care

Water

Only during long dry spells in spring, while the flower stems are growing.

Feeding

A little compost in March; too much feed gives floppy stems.

Support

Usually not needed; among other plants the stems support each other.

Spent flowers

Cut off the spikes if you do not want seedlings; leave the leaves until they turn yellow.

Space

Divide crowded groups every few years.

Tip: Plant it among low perennials in a sunny border and leave it be: more spikes appear every year. On wet clay, plant it in a raised bed instead.

Common cornflag: when to prune it?

When: Common cornflag is not pruned; you only cut off spent spikes and dead leaves.

How:

• After flowering in July, cut off the spent spikes, unless you want it to self-seed.
• Let the leaves yellow and only cut them off once they are brown, usually in August.
• When cutting for the vase, leave as many leaves on the plant as possible.

Pruning calendar and basic rules

Propagation

Cormlets

In August–September, lift a group, separate the small cormlets and replant them straight away. They flower after one to two years.

Seed

It self-seeds freely. You can also sow ripe seed in a pot; seedlings flower after two to three years.

Division

Lift large groups in autumn and spread them over several spots.

Common cornflag: how does it get through the winter?

Hardy to −15 °C: protect young plants.

• Hardy to about −15 °C: in most of Belgium it can simply stay in the ground.
• In cold or wet spots, cover the corms with a layer of leaf mould or straw.
• Wet soil is more dangerous than frost: in clay that stays wet, the corms rot.
• In a pot: keep the pot frost-free in winter or against a wall, and keep the compost dry.

Diseases and pests

• Thrips: Silvery grey streaks on leaves and flowers in a hot, dry summer. Cut off affected parts and hose the plant down with water.
• Corm rot: The corms rot in wet soil. Plant in a well-drained spot.
• Slugs: Eat the young shoots. Pick them off in the evening.
• Too many seedlings: In an open border it can self-seed heavily. Cut off the spikes after flowering.

Through the year

• March: Plant corms. Scatter compost.
• April: Last chance for spring planting.
• May: Flower stems are growing. Water in dry spells.
• June: Flowering. Cut for the vase.
• July: Flowering. Cut off spent spikes.
• August: Leaves die back; cut them off then. Divide groups.
• September: Plant or divide corms.
• October: Plant. Mulch in cold spots.

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 gladiolus means ‘little sword’ in Latin and refers to the sword-shaped leaves.
• Each year a new corm grows on top of the old one, which shrivels away.
• Because the flowers open from the bottom up, a spike stays in flower for a long time, even in a vase.