Broad-leaved dock

How to recognise it

Habit

Perennial, 50–120 cm tall, with a rosette of large leaves and upright, branched flower stems that turn reddish brown in summer.

Leaf

Oblong-oval, up to 25–30 cm, with a heart-shaped base and a blunt tip; edge slightly wavy, veins often red, underside rough-hairy on the veins. Smaller and narrower higher up.

Flower

Small greenish flowers in whorls along long, loose spikes, June to September. Wind-pollinated.

Fruit/Seed

Three-sided nutlet surrounded by three valves with long teeth on the edge; usually one valve carries a small wart. Rusty brown when ripe.

Roots

Thick, yellow, branched taproot that can go more than a metre deep; the top part regrows after being cut.

Confusion with

Curled dock has narrower leaves with a strongly crinkled edge and valves without teeth. Common sorrel is smaller and slimmer, with arrow-shaped, sour-tasting leaves.

Flowering: June–September · Pruning: June–August

Why grow it?

• Food plant of the green dock beetle, a shiny green little beetle, and of the dock bug.
• Caterpillars of the blood-vein, a moth with a pink line across its wings, feed on docks.
• In autumn and winter finches and sparrows eat the seeds from the standing spikes.
• The tall, rusty-brown spikes give structure to a wild corner, even in winter.
• An indicator of fertile ground: where dock is plentiful, the soil is rich in nitrogen.

Broad-leaved dock: where does it grow best?

• In the wild: pastures, hay meadows, field edges, ditch banks, road verges, manure heaps and waste ground.
• Fertile, moist to wet soil, often compacted or disturbed; it prefers clay and loam to poor sand.
• Sun to partial shade.
• In the garden: at most a plant or two in a wild corner, behind the compost heap or along a ditch; not in the vegetable garden or lawn.

Goes well with

• Common nettle: Together they make a wild corner on rich soil, with the nettle as food plant of the peacock and red admiral.
• Common comfrey: Bell flowers for bumblebees, on the same moist, rich soil.
• Meadowsweet: Fragrant plumes on the wet side of the wild corner.
• Purple loosestrife: Purple spikes on wet, fertile soil, loved by bees.

Broad-leaved dock: when and how to plant it?

1. You hardly ever need to plant it: its seed is already in most garden soil and comes up as soon as the ground is bare.
2. If you want it in a wild corner, keep a self-sown seedling in a place where it is not in the way.
3. You can sow in spring or autumn on bare, moist soil; the seed germinates easily.
4. Give a plant at least 60 cm of space, well away from vegetable beds, lawns and fields with cattle or horses.
5. Do not let it seed: cut the flower stems before the seed ripens and you will avoid hundreds of seedlings.
6. Never dig up plants from the wild: it is not needed anyway, as it turns up everywhere by itself.

Care

Water

Not needed; the deep taproot draws water from far down.

Feeding

Never: it already grows too lushly on fertile soil. Manure and compost only make it stronger.

Seeding

Cut flower stems before the seeds turn rusty brown. Seed stays viable in the soil for decades.

Digging out

Lift unwanted plants with a dock fork or narrow spade, preferably after rain; take at least the top 10–15 cm of the root.

Bare patches

In grass and pasture a dense, closed sward helps: seedlings then get no chance. Reseed bare patches straight away.

Tip: Dig out dock after a good downpour: the soil is soft then and the taproot comes out in one piece far more easily.

Pruning and mowing

Pruning months: June–August.

When: From June to August, as soon as the flower stems bloom and before the seeds ripen.

How:

• Cut or mow the flower stems at the base; the leaf rosette can stay.
• If you want to leave spikes for the birds, choose one plant in a place where falling seed does no harm.
• Mowing alone does not kill the plant: the rosette regrows every time.
• Put stems carrying seed in the green waste bin; a cold compost heap does not kill the seed.

Caution: Even cut green stems can still ripen their seed: do not put them on the compost heap.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

The main route: each plant produces an enormous amount of seed every year, which travels with hay, manure, water and soil.

Root pieces

The top part of the taproot regrows after damage; pieces from deeper down do so much less.

Broad-leaved dock: how does it get through the winter?

Hardy to −30 °C.

• The leaves mostly die back; in mild winters a small rosette stays green.
• The rusty-brown seed spikes stay standing, feeding birds and giving the garden structure.
• Fully hardy: the taproot survives hard frost with ease.

Diseases and pests

• Dock beetle: The green beetle and its larvae riddle the leaves with holes. No problem: it is a natural control.
• Rust: Red to brown spots on the leaves. Harmless; leave it.
• Self-seeding: One plant produces thousands of seeds. Always cut flower stems before they ripen.
• Hard to dig out: The root snaps easily. Dig after rain, when the soil is soft, and ease the root out carefully.
• Oxalic acid: The leaves contain oxalic acid. Do not let rabbits, guinea pigs or livestock eat large amounts.

Through the year

• March: Dig out young rosettes in the vegetable garden, preferably after rain.
• April: New leaves. Look for dock beetles and their yellow eggs.
• May: Flower stems appear. Dig out where it is not wanted.
• June: Flowering. Cut flower stems before they set seed.
• July: Cut flower stems, or let one plant seed for the birds.
• August: Cut the last flower stems. The seeds turn rusty brown.
• September: Reseed bare patches in lawn or pasture with grass.
• November: Leave the rusty-brown spikes on the chosen plant.
• December: Finches feed on the seed.

Did you know?

• Dock seed can survive in the soil for decades and germinates as soon as the ground is disturbed.
• The green dock beetle can strip a plant almost bare and is being studied as a natural control for dock in grassland.
• An old folk custom says you should rub a dock leaf on a nettle sting. It has never been proven, but the cool leaf conveniently grows right next to the nettles.