- A mower only shaves the top off a dock, so the quickest fix is to dig out the upper 12 to 15 cm (5 to 6 in) of its root.
- Dock seed stays alive in the soil for many years, so one plant left to seed leaves you fighting its offspring for years.
- Reseed the hole, keep the grass thick and remove any regrowth, and fewer docks find a gap to start in.
A Mower Only Takes the Top Off a Dock, and the Root Below Is What Pays It Back
You know the plant. One big, broad, wavy-edged leaf rosette sits in the lawn. You mow it flat, it grows back, and by summer it has sent up a tall stem that turns rusty red-brown. That is a dock, and mowing alone will not shift it. If it is one of many weeds in the grass, reclaiming a lawn overrun by weeds covers the wider job.
Here is the fix in short. Push a narrow spade straight down beside the plant, and lever out the top 12 to 15 cm (5 to 6 in) of the root. Shake the soil back into the hole and press it flat. Sprinkle grass seed over it in autumn or spring, and remove any regrowth when it appears. Roots deeper than that are unlikely to regrow, so you do not need to chase the whole thing.
Below: why the plant is so stubborn, how to dig it out without leaving a stump, what to do when there are dozens, and how to keep a fresh crop away.
What You Are Looking At and Why It Keeps Returning
Broad-leaved dock has large, oval leaves with slightly wavy edges, about 30 cm (12 in) long and 15 cm (6 in) wide. Curled dock looks similar, but its leaves are slimmer, often no more than 8 cm (3 in) wide, with edges that ripple more. You do not need to tell them apart. Both, and any hybrids between them, are controlled in exactly the same way.
The leaves are the small part. A broad-leaved dock sends a branching taproot down to 1.2 m (4 ft). Cut the leaves and the root stays alive underneath, ready to push up a fresh rosette. Mowing a dock is like snipping the top off a dandelion: the plant loses a few leaves and keeps everything it needs.
Seed is the second problem. In summer the plant raises a flower stem as tall as 1.2 m (4 ft), and the reddish-brown fruits that follow can stand through the winter. A single plant makes large numbers of seed, and that seed stays alive for many years. Gardeners’ World puts it at up to 60 years. Wind, water and animals carry it about, and a bag of manure can bring it in. So a lawn that had no docks last year can have them this year, and a lawn that loses every dock this month still holds a bank of seed.
Seed needs somewhere to land, and docks prefer bare soil and freshly dug ground. They also grow in lawns, where thin turf, worn patches and a very short cut give them a gap. Weeds in general are quick to colonise bare ground where grass growth is patchy, which is why weeds that take over a resting lawn arrive so fast. Once a dock has a taproot, it copes with heavy competition from the grass around it, so catch it young.
Seedlings come up in spring or early autumn. That window is the one to watch in a lawn. A young dock makes a taproot almost straight away, and a small one is far easier to lift than a big one. The earlier you spot it, the less spade work you do.
How to Dig Out a Dock So It Stays Out
Tools first. The best one is a spade with a narrow, deep blade, which cuts a tight cone around the root and leaves the surrounding grass alone. For small plants a hand fork or a long-bladed weeding tool made for dandelions does the same job. A wide, flat spade tears up far more turf than the dock deserves.
Loosen the soil on each side of the plant first, so the root comes out cleanly.
1. Push the narrow spade down close beside the plant, then work around it so the blade runs alongside the root.
2. Slide the spade under the root.
3. Lever back and lift. Aim to bring up the top 12 to 15 cm (5 to 6 in) of root in one piece. Roots deeper than that are unlikely to regenerate, so a long white tail left behind is not a disaster.
4. Shake the soil from the root back into the hole and press it down with your boot.
5. Scatter grass seed on top. Autumn and spring are the two good times to reseed or patch a lawn.
6. Check the spot now and then. If a green shoot appears, dig it out or cut it back.
Dig young plants whenever you can. A small dock has not had time to build a deep root or set seed. Early spring is a good time to catch them, and so is early autumn, when the new seedlings appear.
Some docks sit in awkward places, such as tight against a path or in a hedge base. Take out as much root as you can reach. When the plant sends up new leaves, remove those, and repeat. Each round weakens it.
What goes wrong most often? Gardeners dig the plant out in pieces. Docks regrow from sections of root, so every chopped fragment can become a new plant. Dig it in one clean lift, and if a piece breaks off, search the soil and take it out.
What to Do When There Are Dozens
A lawn with many docks needs patience, not a bigger spade.
**Cut often.** Mowing a dock once does little. Mowing it over and over cuts away each new leaf, and plants need leaves in the light to make their food, so the plant is starved a little more with every cut. Cutting regularly weakens docks and eventually kills them. It takes several years, but it limits soil disturbance, which is better for soil health. Keep the mower going at a sensible height. A very short cut weakens the grass and gives docks bare patches to settle in.
**Hoe off seedlings.** Small plants without a taproot yet come out with a hoe or a quick pull. Choose a warm, dry or windy day, so exposed roots dry out and die before they can settle again.
**Deadhead in summer.** If you spot a rusty stem rising in the grass, cut it off before the seed ripens. This stops self-seeding and limits the spread. Remember that one plant can shed seed that lives for decades.
**Never dig over or rotavate.** It feels like a way to clear the lot in an afternoon, but the machine chops the roots into pieces, and every piece can regrow. One dock becomes many.
**Smother docks that are off the lawn.** On a bed edge or an empty patch, cover the plants with cardboard and then about 20 cm (8 in) of bark or other organic matter. Heavy biodegradable mulch matting works too. Weed fabric, black polythene or old carpet will also do it, as long as the edges are weighed down or buried so no light gets in. Leave it for a year or more. When you lift the cover, expect new seedlings from the old seed, and pull them as they come.
**Skip the burners and the home-made sprays.** Organic weedkillers and flame weeders scorch the leaves and weaken the plant, but they do not kill the root. You can control docks without any weedkiller, and the effort goes into the root, where it counts.
Where the Roots and Seed Should Go
Put the dug-out roots and any seed heads anywhere except the compost heap. A home heap often does not get hot enough to kill them, so roots can survive in the heap, and a fragment of root can regrow. Use your garden waste collection or take them to a recycling centre. If you want to deal with them at home, push them into a stout black plastic sack, such as an old compost bag, fold the top over to keep out the light and leave it for at least a year.
How to Stop Docks Coming Back
Once the lawn is clear, the job is to leave no gaps.
Keep the grass thick. A routine of spring and summer care and an autumn tidy gives dense, healthy turf, which makes it harder for weeds to get started. Raise the cutting height in summer so the grass stays strong. Patch any bare spot with seed or turf in spring or autumn, before a dock gets there first, and see how to stop weeds taking over bare patches for the method.
For a bad patch, cut out the turf with a sharp spade, pull out every weed root, loosen the soil lightly with a fork, rake it level, tread it down and lay fresh turf. Do that before a dock sets seed, not after.
Watch for seedlings in early autumn and spring and hoe or pull them while they are small. Cut off flower stems in summer. Check the lawn edges and any manure or soil you bring in. Seed arrives that way.
Finally, decide where you want docks. They are not all villains. More than 80 insects feed on broad-leaved dock, and the seeds are winter food for birds such as dunnocks and house sparrows. A dock in a wild corner away from the lawn does no harm, and leaving one there means you can stop worrying about every plant. The leaves contain oxalic acid and are toxic to dogs, so keep a dog that chews plants away from the wild patch.
If the lawn is more dock than grass, treat it as a rebuild: lift the turf in sections, clear the roots, reseed or re-lay, and follow with the regular cut. For a very large infestation, call in a gardener.
