Perennial sow-thistle

How to recognise it

Habit

Upright perennial, 60–150 cm, with hollow, sparsely branched stems carrying a loose cluster of flower heads at the top. Damaged stems ooze white milky sap. Often forms patches thanks to its creeping roots.

Leaf

Long and lance-shaped, shallowly to deeply lobed, glossy green, with a margin full of fine, soft prickles. The stem leaves clasp the stem with two rounded lobes.

Flower

Golden-yellow heads of 3–5 cm made up of ray florets only, from July to October. The bracts and flower stalks are often covered in yellow glandular hairs. The heads are mainly open in the morning.

Fruit/Seed

Brown, wrinkled seeds with a soft white parachute of hairs that drifts far on the wind.

Roots

Long, horizontal, brittle roots that send up new shoots in many places. Every piece of root can grow into a new plant.

Confusion with

Smooth and prickly sow-thistle are annuals without creeping roots and with smaller, pale yellow heads of 2–2.5 cm. Dandelion has no leafy stem. Creeping thistle has purple heads and hard spines.

Flowering: July–October · Pruning: March and August–September

Why grow it?

• Flowers late, from July to October, when few other large yellow flowers are left: pollen and nectar for wild bees, bumblebees and hoverflies.
• The fluffy seeds are eaten in late summer by goldfinches and other finches.
• In summer the stems are often covered in aphids: a feast for ladybirds, hoverfly larvae and tits.
• The leaves feed the caterpillars of several moths.
• Young leaves were once eaten as a vegetable, raw or cooked; they taste rather bitter.
• An honest indicator: where it grows in masses, the soil is rich and often disturbed.

Perennial sow-thistle: where does it grow best?

• In the wild in arable fields, waste ground, verges, dykes, ditch banks, rough grassland and, on the coast, along the edge of salt marshes.
• Full sun to light shade.
• Rich, moist to fairly dry soil: clay, loam or sandy loam; it tolerates a little salt.
• In the garden: only where its creeping roots do no harm, such as a wild corner or a rough strip that you mow all round.

Goes well with

• Tansy: Yellow buttons in the same sunny rough patch and in the same late summer.
• Chicory: Sky-blue flower heads beside the golden yellow, also on rich verges.
• Wild teasel: Even more seed for goldfinches in autumn and winter.
• Wild carrot: White umbels for hoverflies on the same verge.
• Meadowsweet: In a damp spot: creamy, fragrant plumes in summer.

Perennial sow-thistle: when and how to plant it?

1. Usually you need do nothing: perennial sow-thistle appears by itself on open, rich soil, from seed or root fragments.
2. If you want it in a wild corner on purpose, sow seed of native origin in September–October or in March–April, where it is to grow, on bare soil.
3. Sow thinly, press the seed in and cover it with no more than a very thin layer of soil. Keep the soil moist until germination.
4. Give the plants 40–50 cm of space and choose a spot you can mow all round, so the roots do not creep into your borders.
5. Never move soil containing root fragments to a vegetable bed or border: every piece can sprout.
6. Never dig up plants in the wild; buy seed from a supplier of native plants.

Care

Water

Not needed: the deep roots find enough water.

Feeding

Not needed. On rich soil it already grows vigorously; fertiliser only makes it stronger.

Spreading

The creeping roots spread further every year. Pull or cut new shoots as soon as they have a few leaves: in time the roots become exhausted.

Vegetable garden

Weed with a garden fork and lift the roots as whole as possible. Do not rotavate or dig: you would chop the roots into pieces that all sprout.

Letting it seed

In a wild corner, let a few plants ripen for the goldfinches and cut the rest before the fluff is released.

Tip: To get rid of it in the vegetable garden, never rotavate; instead dig out the shoots as soon as they appear. Persistence pays: in time the roots become exhausted.

Pruning and mowing

Pruning months: March and August–September.

When: In August–September, cut off the faded stems before the seed ripens; the last stems in March.

How:

• Cut the flowering stems when most heads have faded, before the fluff is released, if you do not want seedlings.
• Leave a few stems for the birds and cut them only in March.
• Leave hollow stems standing in winter: small insects shelter inside.
• Mow a rough verge or corner once a year, in September, and remove the cuttings.

Caution: Do not rotavate or dig where perennial sow-thistle grows: every piece of root becomes a new plant.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Ripens from August and blows away with its fluff. Sow in autumn or spring where it is to grow, on bare soil.

Root pieces

A piece of root a few centimetres long sprouts easily in spring. This is also how the plant spreads when soil is dug or rotavated.

Perennial sow-thistle: how does it get through the winter?

Hardy to −30 °C.

• The parts above ground die back in autumn; the plant overwinters with its roots in the soil.
• A few dead stems left standing give small insects a place to shelter.
• Fully hardy, even in severe winters.
• In April–May new shoots come up from the roots, often in a line along the horizontal roots.

Diseases and pests

• Spreading: In a vegetable bed or border it can quickly take over a large area. Remove the shoots every time and do not rotavate.
• Self-seeding: The fluff travels far. Cut the flowering stems before the seed ripens.
• Aphids: In summer the tips are often covered in aphids. Leave them for the ladybirds; the plant hardly suffers.
• Powdery mildew: White powder on the leaves in dry late summers. Harmless; cut out badly affected stems.

Through the year

• March: Cut old stems. In the vegetable garden, dig out the first shoots.
• April: New shoots appear from the roots. You can still sow.
• May: Shoots grow fast; in the vegetable garden remove them every week.
• June: The flowering stems shoot up.
• July: Flowering begins; in the morning wild bees and hoverflies visit the heads.
• August: Full flower. Cut faded stems if you do not want seed.
• September: Flowers and ripening seed; goldfinches come to feed. Mow the wild corner. Sowing possible.
• October: Last flower heads. Leave a few stems standing.
• November: The plant dies back above ground and rests in the soil.

Did you know?

• Sow-thistles are not true thistles: they are related to dandelion and lettuce, with white milky sap and soft prickles instead of hard spines.
• The flower heads open in the morning and often close again during the afternoon; on a grey day they sometimes stay shut.
• The name sow-thistle refers to female pigs: according to tradition, pigs were very fond of the plant.