Knotweed, Douglas' knotweed, Austin knotweed, Engelmann's knotweed, Johnston's knotweed, Large kno

Polygonum douglasii

Physical Characteristics

Polygonum douglasii is a ANNUAL growing to 0.3 m (1ft). 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 dry or moist soil.

Distribution

N. America - Northwest Territory to British Columbia, south to Vermont, New Mexico and Oklahoma.

Habitats

Cultivated Beds;

Edible Uses

Edible Parts: Leaves Seed Edible Uses: Leaves - raw or cooked. Seed - dried then ground into a powder and mixed with cornmeal or other cereals for making bread etc[46, 61, 105, 161, 257]. The seed is rather small and fiddly to utilize, it is enclosed in a dry papery hull[207].

Medicinal Uses

None known

Known Hazards

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[238].