Water Smartweed
Polygonum coccineum

Family: Polygonaceae

What it is like

Polygonum coccineum is a PERENNIAL growing to 0.5 m (1ft 8in). See above for USDA hardiness. It is hardy to UK zone 5. The species is hermaphrodite (has both male and female organs) and is pollinated by Insects. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers wet soil and can grow in water.

Height (m): 0.5

Where it is found

Ponds and damp ground by streams, lakes etc.

Western N. America - Quebec to California.

Conservation Status:

Countries/locations it is found in

How it is used

Food

Rating: 1

Young shoots - cooked. Used in the spring. Seed - raw or cooked. It is rather small and fiddly to utilize.

Seed: includes nuts, cereals, peas and beans.

Medicine

Rating: 0

Other

Rating:

How it is grown

A water plant, succeeding in shallow water or a bog garden. Tolerates most soils but repays generous treatment. The stems of this plant root at the nodes wherever they come into contact with the soil. Plants seem to be immune to the predations of rabbits.

Propagating it: Seed - sow spring in a cold frame. Germination is usually free and easy. When they are large enough to handle, prick the seedlings out into individual pots and plant them out in the summer if they have reached sufficient size. If not, overwinter them in a cold frame and plant them out the following spring after the last expected frosts. Division in spring or autumn. Very easy, larger divisions can be planted out direct into their permanent positions. We have found that it is better to pot up the smaller divisions and grow them on in light shade in a cold frame until they are well established before planting them out in late spring or early summer.

Best place to grow: Pond; Bog Garden;

Habit: Perennial

Hardiness: 4-8

Growth:

Soil: Light (sandy), medium, heavy (clay)

Shade: Semi-shade, no shade

Moisture: Wet, water

Things to keep in mind

Although no specific mention has been made for this species, there have been reports that some members of this genus can cause photosensitivity in susceptible people. Many species also contain oxalic acid (the distinctive lemony flavour of sorrel) - whilst not toxic this substance can bind up other minerals making them unavailable to the body and leading to mineral deficiency. Having said that, a number of common foods such as sorrel and rhubarb contain oxalic acid and the leaves of most members of this genus are nutritious and beneficial to eat in moderate quantities. Cooking the leaves will reduce their content of oxalic acid. People with a tendency to rheumatism, arthritis, gout, kidney stones or hyperacidity should take especial caution if including this plant in their diet since it can aggravate their condition.

Its other names

Local names

Synonyms

P. muehlenbergii. (Meisn.)Wats. Persicaria muehlenbergii. (Meisn.)Small.