Threadleaf coreopsis

Threadleaf coreopsis: how do you recognise it?

Habit

A dense, airy clump of upright stems, about 50 cm tall and 45 cm wide.

Leaves

Thread-fine and needle-like, in whorls around the stem.

Flower

Countless small, star-shaped flowers about 3 cm across, from June to September.

Colour

Golden yellow to pale yellow, depending on the variety.

Roots

A shallow rootstock with short underground runners; the clump widens slowly.

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

Why grow it?

• Flowers all summer, from June to September, with a second flush after a trim.
• Tolerates drought and heat: ideal for a sunny, dry border or a gravel garden.
• The fine, needle-like leaves give an airy texture, even when it is not in flower.
• Bees and butterflies find nectar and pollen in it all summer.
• Long-lived and low-maintenance, without becoming invasive.

Threadleaf coreopsis: where does it grow best?

• Full sun: in shade it flops open and flowers less.
• Well-drained sandy or loamy soil; acid, neutral or chalky.
• Dry to normally moist. It dislikes wet soil, especially in winter.
• At the front or middle of a sunny border, in a gravel garden or in a large pot.
• Allow 40–45 cm between plants.

Light

Sun

Soil type

Sand or loam

Acidity

Not fussy

Moisture

Dry or normal

Size

0.5 m tall, 0.45 m wide

Hardiness

Hardy (to -35 °C)

Goes well with

• Sage: Violet-blue spikes as a contrast to the yellow stars.
• Catmint: Soft blue for the same dry, sunny spot.
• Ornamental grasses: Fine stems that add to the airy texture.
• Speedwell: Blue spikes that flower at the same time.
• Yarrow: Flat flower heads beside the little stars, and also drought-tolerant.

Threadleaf coreopsis: when and how to plant it?

Plant in March–May and September.

1. Plant in March–May or in September.
2. Dig a hole slightly larger than the pot; on heavy soil, mix in coarse sand or gravel.
3. Set the plant at the same depth as in the pot and firm the soil.
4. Space plants 40–45 cm apart.
5. Water well straight away and in dry spells for the first weeks.
6. Do not feed; a gravel mulch keeps the base dry.

Care

Watering

In dry spells in the first year; after that rarely needed, except in pots.

Feeding

Do not feed: on rich soil it flops and flowers less.

Trimming

After the first flush of flowers, lightly trim the whole clump with shears: a second flowering follows.

Deadheading

There are too many flowers to remove one by one; trimming works better.

Dividing

Every three to four years in spring, when the centre goes bare.

Tip: After the first flush, lightly trim the whole clump with shears: a few weeks later it flowers again into September. Do not feed it, and it stays compact.

Threadleaf coreopsis: when to prune it?

Pruning months: March and July.

When: Trim lightly in July after the first flush of flowers, and cut the old stems down in March.

How:

• In July, cut the whole clump back by about a third, to just below the faded flowers.
• After a few weeks a new flush of flowers follows, lasting into September.
• Leave the stems over winter and cut them down to just above the ground in March.

Caution: It emerges late in spring: do not dig it up by mistake if you still see nothing in April.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In March–April. Take pieces from the edge, each with a few shoots and roots, and replant at once.

Cuttings

In April–May, take 5–8 cm cuttings from young shoots and root them in sandy compost.

Threadleaf coreopsis: how does it get through the winter?

Hardy to −35 °C.

• Very hardy, to about −35 °C: no protection is needed.
• Wet soil in winter is more dangerous than frost; make sure drainage is good.
• Leave the old stems until March.
• In a pot: keep it sheltered and make sure water drains away well.

Diseases and pests

• Slugs: In spring they eat the young shoots as soon as they appear. Pick them off in the evening.
• Rot: In heavy, wet soil the clump rots in winter. Plant in a drier spot or a raised bed.
• Flopping: Soil too rich or too little sun. Do not feed and move it to a sunnier spot.
• Bare centre: Older clumps go bare in the middle. Divide them in spring.

Through the year

• March: Cut down old stems. Divide and plant.
• April: Plant. Be patient: it emerges late. Watch for slugs.
• May: Plant. Take cuttings.
• June: Flowering begins.
• July: After the first flush, trim lightly.
• August: Second flush. Water pots in dry spells.
• September: Flowering. Planting is still possible.
• November: Leave the stems standing for winter.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Butterflies

Nectar for butterflies.

Did you know?

• The name Coreopsis comes from Greek and means roughly ‘bug-like’: the flat seeds look like small insects. That is why it is also called tickseed in English.
• The species name verticillata means ‘whorled’ and refers to the leaves, which grow in whorls around the stem.