Curled dock

How to recognise it

Habit

Perennial with a rosette of large leaves and, in summer, an upright, often reddish flowering stem of 50–100 cm, sometimes up to 150 cm.

Leaf

Long and narrowly lance-shaped, 15–30 cm, with a strongly waved, crisped edge. The base is tapered or rounded, never heart-shaped. Hairless, fresh green.

Flower

Small green flowers in whorls, packed into a narrow, upright spike, from June to October. Wind-pollinated.

Fruit/Seed

Three-angled nutlet, enclosed by three heart-shaped, untoothed valves that each carry a small swelling, often one larger than the other two. Rusty brown when ripe.

Roots

Thick, yellow taproot that goes deep. Mainly the top part of the root regrows if you cut the plant off.

Confusion with

Broad-leaved dock has much broader leaves with a heart-shaped base and toothed fruit valves. Common sorrel and sheep’s sorrel are smaller, taste sour and have arrow-shaped leaf bases.

Flowering: June–October · Pruning: March, July and September

Why grow it?

• Food plant for the caterpillars of moths such as the blood-vein and several noctuids, and for the green dock beetle, a small, shiny green beetle.
• The seeds stay on the plant all winter and feed finches, sparrows and other seed-eaters.
• The rusty brown seed spikes are a striking sight in autumn and winter and look good in dried arrangements.
• Small insects and spiders shelter in the dead stems and seed heads in winter.
• The young leaves were once eaten cooked, like spinach; because of the oxalic acid, always in moderation.
• An honest indicator: where curled dock thrives, the soil is rich, disturbed or trampled.

Curled dock: where does it grow best?

• In the wild: verges, pastures, field edges, ditch banks, waste ground, building sites and the strandline along the coast.
• Full sun to light half shade.
• Rich, often disturbed or trampled soil: clay, loam or sand, from moist to fairly dry.
• In the garden it belongs in a rough corner or a wild verge, not in the vegetable patch or a poor wildflower meadow.

Goes well with

• Common nettle: Together a rough corner full of food plants for caterpillars.
• Wild teasel: Another tall seed plant for birds that stands all winter.
• Tansy: Yellow buttons beside the brown dock spikes, both tough plants of a rough verge.
• Wild carrot: White umbels in the same sunny, rough verge.

Curled dock: when and how to plant it?

1. Usually you do not need to plant it: curled dock turns up by itself, from seed carried by birds, wind, water or imported soil.
2. If you want a few plants for insects and birds, buy seed from a nursery or seed supplier specialising in native plants. Never dig plants up from the wild.
3. Sow in March–April or in September on an open spot and barely cover the seed: it germinates in the light.
4. Choose a permanent spot straight away, because the taproot makes moving it later difficult. One or two plants 50 cm from other plants are enough.
5. Water only until the seedlings are well established; after that it looks after itself.

Care

Water

Not needed: the taproot draws water from deep in the soil.

Feeding

Never. On rich soil it already grows more than enough.

Letting it seed

If you do not want it to self-seed, cut the spikes as soon as they start to turn brown. Leave one or two at most for the birds.

Spreading

Dig out unwanted plants with a dock lifter or narrow spade when the soil is moist, removing the top part of the root as well.

Seedlings

Weed out young seedlings straight away: the taproot is still small and they pull up roots and all.

Tip: Learn to tell curled dock from broad-leaved dock and sorrel, and dig out unwanted plants while they are young: a seedling comes up roots and all, a two-year-old plant does not.

Pruning and mowing

Pruning months: March, July and September.

When: In July, cut the first flowering stems if you want to limit self-seeding, the rest in September. Stems you leave for the birds are cut in March.

How:

• Cut the flowering stems just above the leaf rosette before the seeds ripen; the rosette itself stays.
• Leave one or two stems standing through winter for the birds and cut them in March.
• Do not put spikes with ripe seed on the compost heap: the seeds often survive there.
• Mowing alone will not get rid of it: the plant quickly regrows from the root.

Caution: The seed stays viable in the soil for years, even decades: letting it seed for just one year means years of work.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Self-seeds freely. To sow it yourself: in March–April or in September on bare soil, barely covered.

Root pieces

The top part of the taproot regrows. So it also spreads when soil is dug or rotavated: do not dig pieces of root back in.

Curled dock: how does it get through the winter?

Hardy to −30 °C.

• The large leaves mostly die back, but in mild winters young leaves often stay green in the heart of the rosette.
• The rusty brown seed spikes stand until spring and feed seed-eating birds.
• Fully hardy: the taproot survives severe frost down to about −30 °C without any trouble.

Diseases and pests

• Green dock beetle: The shiny green beetles and their larvae chew holes in the leaves in spring. Harmless: they belong with the plant.
• Rust: Small orange-brown spots on the leaves. No action needed.
• Self-seeding: One plant produces thousands of seeds. Cut the spikes before they ripen.
• Deep root: Pulling it up rarely works. Dig it out when the soil is moist and remove the root crown completely; repeat if new leaves appear.
• Oxalic acid: The leaves contain oxalic acid. Keep large amounts away from grazing animals, for example in hay.

Through the year

• March: Cut the stems you left for the birds. Weed out seedlings. Sow.
• April: New rosettes grow. Dig out unwanted plants while the soil is moist.
• May: Dock beetles on the leaves. The flowering stems shoot up.
• June: Flowering begins. The wind spreads the pollen.
• July: Full flower. Cut the flowering stems to limit self-seeding.
• August: The fruits turn rusty brown.
• September: Cut the last spikes or leave one or two for the birds. Sow.
• October: Late flowers. Ripe seeds drop.
• November: Birds feed on the seeds.
• December: Rest. The brown spikes decorate the rough corner.

Did you know?

• The species name ‘crispus’ means curled and refers to the wavy leaf edge, just like the English name curled dock.
• Each fruit has three valves with corky swellings. Thanks to these the seeds float, so the plant also spreads along streams and rivers.
• Like sorrel and rhubarb, curled dock owes its sour taste to oxalic acid.