Persicaria decipiens aka Slender Knotweed

Persicaria decipiens is an annual plant in the knotweed family, Polygonaceae. It lives for one year. Its native range spans the Old World's tropical and subtropical zones to Australasia. Kew places it in a subtropical climate zone. It is not native to Britain or Ireland. Older sources may use the name Polygonum salicifolium for it. People gather it from the wild for local food and folk remedies.

This thin plant has weak stems and a low, loose form. Its listed height is about 1.6 feet [0.5 metres]. The stems can grow to 3.9 feet [1.2 metres] long. They may stand upright or trail across the ground. Trailing stems may root at nodes, the joints that touch soil. So stem length does not show how tall it stands. The evidence gives no flower colour or fruit shape for this species.

Wet ground forms a clear part of its habitat. It grows along river banks, in swamps, and sometimes in water. Some records place it in dark, damp clay near water. In gardens, it grows in plain soil but likes soil that stays moist. The soil need not be rich. Sun or part shade suits it. New plants are easy to grow from seed. The source says the seeds sprout with little trouble. Move young plants into their own pots when large enough to handle. Let them grow more before you plant them out.

Take care when choosing a garden site, as this plant spreads. It has become a weed beyond its native range. Reports come from places with temperate climates and from the tropics. Seeds float, so flowing water can take them to new sites. They can also mix with crop seed or animal feed. Animals may eat the seeds, then pass them in dung. These routes help it spread beyond wild or planted groups. One source says rabbits seem to leave the plants alone.

People eat the leaves raw or cooked. They also chop and boil young leaves and shoots. They may serve these with rice or another staple food. Cooked leaves feel coarse and turn slimy. They have little appeal, so have more use when other foods run short. Ash from burnt plants also serves in place of salt. Folk remedies use ash for sore throats and tonsillitis, or swollen tonsils. Other records note leaf mixes used to purge the bowels or treat skin. These are folk uses, not proof that they help health. The evidence gives no toxicity rating for this species.