Greater burdock

How to recognise it

Growth habit

Biennial: in the first year a large leaf rosette, in the second a much-branched flowering stem of 1–2 m.

Leaf

Very large, up to 50 cm, heart-shaped with a wavy edge; green above, grey and felted beneath. The stalks of the lower leaves are solid, not hollow.

Flower

Globular heads of 3–4 cm with purple tubular florets, on long stalks in a loose, flat-topped cluster, surrounded by green bracts with hooked tips. From July to September.

Fruit/seed

Elongated, grey-brown seeds with a short pappus that stay inside the bur: the whole head hooks on and so spreads the seeds.

Roots

A long, thick taproot that goes deep into the ground.

Confusion with

Lesser burdock (Arctium minus) has smaller heads of 1.5–2.5 cm on short stalks, more in clusters along the stem, and hollow leaf stalks. Butterbur also has huge leaves that are grey beneath, but it grows in wet places and flowers in early spring, before the leaves appear.

Flowering: July–September · Pruning: March and September

Why grow it?

• A rich nectar source in July–September for bumblebees, bees, hoverflies and butterflies.
• Goldfinches and other finches pick the seeds from the faded heads in autumn and winter.
• An imposing structural plant for a wild corner, with huge leaves that give shade and shelter to small animals.
• In Japan the root is a cultivated vegetable, gobo, and it was once eaten in Europe too.
• A wonderful example of seed dispersal by animals, to show children.

Greater burdock: where does it grow best?

• In the wild: rough ground, verges, river and ditch banks, woodland edges, farmyards and waste ground.
• Sun to part shade.
• Normal, deep and fertile soil; it likes nitrogen-rich spots.
• Give it room: a plant in flower is soon 1 m across. A wild corner, a rough strip or the edge of an orchard is ideal.

Goes well with

• Wild teasel: Another bold biennial structural plant, whose seeds goldfinches eat.
• Common nettle: For a wild corner, with food plants for peacock and red admiral caterpillars.
• Hemp-agrimony: Pink flower clusters in late summer, on the same rich soil.
• Tansy: Yellow buttons in late summer for a rough strip.

Greater burdock: when and how to plant it?

1. Buy seed of wild origin from a native plant nursery or collect a few ripe burs from a garden.
2. Sow where it is to grow, as the taproot resents being moved. Sow in September–October or March–April.
3. Place the seeds in twos or threes 1 cm deep, 80–100 cm apart, and thin later to one plant.
4. Water until the seedlings are growing well; after that it is no longer needed.
5. Do not plant it beside a path where dogs walk, as the burs get into their coats.
6. Never dig up plants from the wild.

Care

Water

Only for young plants; the deep taproot finds its own water.

Feeding

Not needed; it already likes rich soil.

Letting it seed

Leave a few heads for the goldfinches; cut off the rest if you do not want seedlings.

Clearing up

After setting seed the plant dies. Dig out the taproot or let it rot down in the soil.

Spreading

Pull up seedlings in spring while the taproot is still small.

Tip: If you want burdock for the birds but not in your dog’s coat, put it at the back of a wild corner, behind a low hedge or a pile of branches, where your animals do not brush past.

Pruning and mowing

Pruning months: March and September.

When: In September, cut off the burs if you do not want them; in March, remove the dead stems.

How:

• Cut off faded heads before they turn brown and clingy if you want neither seedlings nor burs in your dog’s coat.
• Leave a few stems with burs for the birds.
• In March, cut the dead stems off at the base.
• Do not remove the large first-year leaves: the rosette needs them to flower the following year.

Caution: Wear gloves and old clothes: the burs hook into everything.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Collect ripe, brown burs in September–October, pick out the seed wearing gloves and sow in place in autumn or spring.

Self-seeding

If burs drop nearby, seedlings come up of their own accord.

Greater burdock: how does it get through the winter?

Hardy to −30 °C.

• First-year plants die back; the taproot overwinters and sprouts again in spring.
• Second-year plants die after setting seed, but the dry stems with burs remain standing.
• Goldfinches and other finches come for the seeds in winter.
• Fully hardy, to about −30 °C.

Diseases and pests

• Burs in fur: Dogs, cats and horses come home with burs in their coats. Cut off the heads or plant it away from paths.
• Too many seedlings: On rich soil it self-seeds heavily. Pull up seedlings while young.
• Aphids: Colonies on stems and leaves; ladybirds and hoverfly larvae deal with them.
• Powdery mildew: White powder on the large leaves in late summer; harmless for a plant that dies anyway.

Through the year

• March: Cut off dead stems. Sow in place.
• April: Rosettes sprout again. Thin seedlings.
• May: On second-year plants the flowering stems shoot up.
• July: Flowering begins: bumblebees and butterflies.
• August: Full flower.
• September: Cut off burs if you do not want seedlings. Collect and sow seed.
• October: The burs ripen; goldfinches come for the seeds.
• December: Dry stems with burs stay standing for the birds.

Did you know?

• The hook-and-loop fastener was devised in the 1940s by the Swiss engineer George de Mestral, after he examined under a microscope the hooks of burs he had picked up on a walk with his dog.
• In Japan the root is grown as a vegetable called gobo.
• The genus name Arctium probably comes from the Greek arktos, bear, after the rough, bristly heads.