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Polygonum douglasii - Greene.

Common Name Knotweed, Douglas' knotweed, Austin knotweed, Engelmann's knotweed, Johnston's knotweed, Large kno
Family Polygonaceae
USDA hardiness Coming soon
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].
Habitats Rocky slopes and dry soils all over N. America[43, 60].
Range N. America - Northwest Territory to British Columbia, south to Vermont, New Mexico and Oklahoma.
Edibility Rating    (2 of 5)
Other Uses    (0 of 5)
Weed Potential No
Medicinal Rating    (0 of 5)
Care (info)
Well drained soil Moist Soil Semi-shade Full sun
Polygonum douglasii Knotweed, Douglas


USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York. Vol. 1
Polygonum douglasii Knotweed, Douglas
Patrick J. Alexander @ USDA-NRCS PLANTS Database

 

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Summary


Physical Characteristics

 icon of manicon of flower
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.

UK Hardiness Map US Hardiness Map

Synonyms

Plant 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].

References   More on Edible Uses

Medicinal Uses

Plants For A Future can not take any responsibility for any adverse effects from the use of plants. Always seek advice from a professional before using a plant medicinally.


None known

References   More on Medicinal Uses

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Other Uses

None known

Special Uses

References   More on Other Uses

Cultivation details

We have very little information on this species and do not know if it is hardy in Britain, though judging by its native range it should succeed outdoors in most parts of the country. The following notes are based on the general needs of the genus. Succeeds in an ordinary garden soil[1] but prefers a moisture retentive not too fertile soil in sun or part shade[200]. Repays generous treatment[1]. Plants seem to be immune to the predations of rabbits[233].

References   Carbon Farming Information and Carbon Sequestration Information

Temperature Converter

Type a value in the Celsius field to convert the value to Fahrenheit:

Fahrenheit:

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Plant Propagation

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.

Other Names

If available other names are mentioned here

Native Range

NORTHERN AMERICA: Canada (Yukon, Québec, Ontario, Saskatchewan, Alberta, Manitoba, British Columbia, Michigan, New Hampshire, New York, Vermont), United States (Iowa, Minnesota, Nebraska, South Dakota, Colorado, Idaho, Montana, Oregon, Washington, Wyoming, Virginia, New Mexico, Arizona, California, Nevada, Utah)

Weed Potential

Right plant wrong place. We are currently updating this section. Please note that a plant may be invasive in one area but may not in your area so it’s worth checking.

Conservation Status

IUCN Red List of Threatened Plants Status :

Related Plants
Latin NameCommon NameHabitHeightHardinessGrowthSoilShadeMoistureEdibleMedicinalOther
Polygonum alaskanumAlaska Wild RhubarbPerennial1.8 -  LMHSNM21 
Polygonum alpinumAlpine Knotweed, Alaska wild rhubarbPerennial1.0 4-8  LMHSNM21 
Polygonum amphibiumWillow Grass, Water knotweed, Longroot smartweed, Water smartweedPerennial0.3 4-8  LMHSNWeWa121
Polygonum arenastrumSmall-Leaved Knotweed, Oval-leaf knotweedAnnual0.3 4-8  LMHSNM231
Polygonum aviculareKnotweed, Prostrate knotweedAnnual0.3 4-8  LMHSNM231
Polygonum barbatumJoint WeedPerennial0.8 -  LMHSNM11 
Polygonum bistortaBistort, Meadow bistort, SnakeweedPerennial0.5 4-7 FLMHSNMWe332
Polygonum bistortoidesAmerican BistortPerennial0.5 4-8  LMHSNM31 
Polygonum bungeanumBunge's smartweedAnnual0.8 0-0  LMHSNM10 
Polygonum coccineumWater SmartweedPerennial0.5 4-8  LMHSNWeWa10 
Polygonum conspicuum Perennial0.6 -  LMHSNM10 
Polygonum convolvulusBlack BindweedAnnual1.2 0-0  LMHSNM100
Polygonum divaricatum Perennial1.0 -  LMHSNDM10 
Polygonum dumetorumClimbing false buckwheatAnnual1.8 0-0  LMHSNM11 
Polygonum equisetiforme Perennial1.0 7-10  LMHNDM102
Polygonum fugax Perennial0.0 -  LMHSNM30 
Polygonum hydropiperSmartweed, Marshpepper knotweedAnnual0.8 0-0  LMHNWeWa221
Polygonum japonicumJapanese Knotweed, Mexican Bamboo, Japanese KnotweedPerennial3.0 4-10 FLMHSNM333
Polygonum lapathifoliumCurlytop KnotweedAnnual0.8 4-8  LMHSNMWe111
Polygonum limosum Perennial1.8 -  LMHSNM10 
Polygonum longisetumOriental lady's thumbAnnual0.5 0-0  LMHSNMWe10 
Polygonum maackianum Annual0.8 -  LMHSNMWe10 
Polygonum manshurienseAsian BistortPerennial0.8 -  LMHSNMwe01 
Polygonum microcephalum Perennial0.5 -  LMHSNM10 
Polygonum minusPygmy smartweedAnnual0.3 0-0  LMHSNMWe10 
Polygonum molle Perennial2.5 6-9 FLMHSNM212
Polygonum multiflorumHe Shou Wu, Tuber fleeceflowerPerennial Climber4.5 6-9  LMHSNM23 
Polygonum nepalenseNepalese smartweedAnnual0.3 0-0  LMHSNMWe111
Polygonum orientalePrince's Feather, Kiss me over the garden gateAnnual1.5 0-0  LMHSNM220
12

Growth: S = slow M = medium F = fast. Soil: L = light (sandy) M = medium H = heavy (clay). pH: A = acid N = neutral B = basic (alkaline). Shade: F = full shade S = semi-shade N = no shade. Moisture: D = dry M = Moist We = wet Wa = water.

 

Expert comment

Author

Greene.

Botanical References

4360235

Links / References

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