Perennial cornflower

Perennial cornflower: how do you recognise it?

Habit

Broad clump 40–50 cm tall and up to 60 cm wide, spreading by runners.

Leaves

Lance-shaped, up to 15 cm long, grey-green and woolly underneath; the leaf base runs down the stem as a narrow wing.

Flower

Single flower heads about 5 cm across, with deeply cut, spidery outer florets around a centre of small tubular florets, from May to July.

Colour

Cornflower blue with a reddish-purple centre; varieties also in white, pink and purple.

Roots

Creeping rhizomes and runners, with which it spreads quickly in rich soil.

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

Why grow it?

• Early flowers, from May to July, with a repeat flush if you cut it back in June.
• Bees, bumblebees and butterflies love the flowers.
• An unusual flower shape: ragged blue rays around a purple centre.
• Easy and tough: grows in almost any soil, in sun or part shade, and tolerates drought.
• Fully hardy and low-maintenance.

Perennial cornflower: where does it grow best?

• Sun or part shade; in sun it stays more compact and flowers more freely.
• Sand, loam or clay, acid to chalky. Ordinary garden soil is fine; in rich soil it spreads more and flops sooner.
• Dry to normally moist and well drained; it dislikes wet feet in winter.
• Plant 40–50 cm apart; give it room or put it where spreading does no harm.

Light

Sun and partial shade

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Dry or normal

Size

0.5 m tall, 0.6 m wide

Hardiness

Hardy (to -35 °C)

Goes well with

• Oriental poppy: Red or orange beside blue in May–June, and it is also cut back after flowering.
• Columbine: Flowers at the same time, in sun or part shade.
• Lady’s mantle: Lime-green sprays as a soft edging beside the blue.
• Hardy geranium: Fills the gap once the perennial cornflower has been cut back after flowering.

Perennial cornflower: when and how to plant it?

Plant in March–April and September–October.

1. Plant in March–April or September–October.
2. Loosen the soil; on poor soil mix in some compost, on rich soil there is no need.
3. Set the plant at the same depth as it was in its pot and firm the soil.
4. Leave 40–50 cm between plants.
5. Water well straight away, then in dry spells for the first few weeks.

Care

Water

In dry spells after planting; after that only in long dry periods.

Feeding

Not needed, or a thin layer of compost in March. Too much feed gives floppy stems and more spreading.

Cutting back

In June, after the first flush, cut the whole plant back to just above the ground for fresh leaves and a repeat flush.

Support

In rich soil or shade the stems flop open; a low plant support in April helps.

Runners

Every spring, slice off runners outside its space with a spade.

Tip: Put it where it may spread a little, for example among sturdy perennials, and cut it back in June after flowering: in July you will have fresh leaves instead of a tatty, grey clump.

Perennial cornflower: when to prune it?

Pruning months: March and June.

When: In June, after the first flush, cut the whole plant back to just above the ground. In March, clear away dead leaves.

How:

• Cut all stems and leaves back to 5 cm above the ground.
• Then water and add some compost: within a few weeks fresh leaves appear, often followed by a smaller repeat flush in late summer.
• In between, cut off faded flowers if you do not want seedlings: it self-sows readily.
• In March, clear away old, dead leaves.

Caution: Do not wait too long to cut it back: after flowering the clump flops open and the leaves often get powdery mildew.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In March–April or September–October: lift a clump or slice off a piece from the edge and replant it elsewhere straight away. Dividing every 3–4 years keeps the plant young.

Self-sown seedlings

It often self-sows. Move the seedlings in spring; varieties do not always come true from seed.

Perennial cornflower: how does it get through the winter?

Hardy to −35 °C.

• Fully hardy, to about −35 °C: no protection needed.
• The leaves largely die down in winter; it shoots again in March.
• In a pot: stand it against a wall and make sure water drains away freely.

Diseases and pests

• Powdery mildew: White powder on the leaves, especially after flowering and in dry weather. Cut the plant back: the new leaves are healthy. Water in dry spells.
• Flopping stems: In rich soil or too much shade the stems flop open. Use a low support, do not feed and cut back after flowering.
• Spreading: Runners and seedlings pop up everywhere. Slice off runners and cut off faded flowers.
• Slugs: Eat the young shoots in spring. Pick them off in the evening.

Through the year

• March: Clear dead leaves. Plant or divide.
• April: Plant. Put in a low support. Slice off runners.
• May: Flowering starts. Bees and butterflies on the flowers.
• June: After the first flush, cut back to just above the ground. Water and add compost.
• July: Fresh leaves. Water in dry weather.
• August: Sometimes a repeat flush. Cut off faded flowers.
• September: Plant or divide.
• October: Plant.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Butterflies

Nectar for butterflies.

Did you know?

• What look like ragged petals are in fact enlarged, sterile tubular florets around the edge of the flower head. They lure insects to the small, fertile florets in the centre.
• It is related to the annual cornflower; hence its English name, perennial cornflower.
• ‘Montana’ means ‘of the mountains’: in the wild it grows in mountain meadows in central and southern Europe.