Horseradish
Armoracia rusticana
A coarse perennial crucifer forming a clump of long, glossy, dock-like leaves with wavy toothed edges, rising from a thick pale taproot. The root is what is wanted: grated raw it gives a fierce mustard heat that fades within about an hour, so sauces are best made just before eating. Sprays of small white four-petalled flowers appear in early summer, but British plants rarely set seed and spread instead from broken root fragments.
An established naturalised alien, originally from south-east Europe and western Asia. Found on roadsides, railway embankments, field margins, waste ground and riverbanks through lowland Britain and Ireland, favouring deep, moist, disturbed soil in full sun, and often persisting for decades around old gardens and allotment sites.
The root is eaten as a condiment rather than a vegetable, and quantity is the limit: large amounts of raw root irritate the mouth and stomach. The volatile oil released by grating is a strong irritant, so work in a ventilated space and keep it away from the eyes; prolonged handling can redden or blister the skin. Digging the root needs the landowner's permission, since uprooting any wild plant without it is an offence under the Wildlife and Countryside Act 1981.
Always use more than one reference to confirm a plant. You are responsible for what you choose to forage.
Leaf clump
Basal leaves reach 30-60 cm, oblong to spoon-shaped, dark glossy green with wavy, bluntly toothed margins, each on a long stout stalk. From a distance the clump reads as a dock, but the leaves are broader, more crinkled and coarser in texture, with a thick pale midrib.
Root
A thick, branching, yellowish-white taproot running 30 cm or more down, tough and fibrous rather than crisp. Scraped or snapped it smells sharply of mustard within seconds. No heat means it is not horseradish, whatever the leaves suggested.
Flowers
Loose branched sprays of small white four-petalled flowers on stems up to about a metre, from May into July. Seed pods are usually absent or empty in Britain, which is why colonies stay put and thicken rather than appearing in new places.
Growth habit
Forms dense, long-lived colonies from root fragments, so plants are almost always in patches rather than as scattered singles. Any piece of root left in the ground when digging will regrow, which matters if you are harvesting on someone else's land.
Updated 2026-08-08T06:52:58.111Z · Part of the shared Foragers Log catalogue · Herb