Douglas's knotweed
Polygonaceae (Buckwheat family)
Introduction to Vascular Plants
Introduction
Polygonum douglasii is a native wetland species that is found across much of Canada (AB, BC, MB, ON, QC, SK) and the US (AZ, CA, CO, IA, ID, MD, ME, MI, MN, MT, ND, NE, NH, NM, NV, NY, OR, SD, UT, VT, WA, WY) (USDA 2010).
In the Illustrated Flora of British Columbia, several subspecies of P. douglasii were recognized. However, the nomenclature for this species has changed. The BC Conservation Data Centre, which determines the official list of BC plants, says: "In 2007, we decided to follow Flora North America (FNA) volume 5 which treats P. douglasii in the narrow sense and elevated the following subspecies as distinct species: ssp. austiniae, ssp. majus, ssp.nuttallii, ssp. engelmannii and ssp. spergulariiforme. This differs from how Kartesz (1999) treats P. douglasii ssp. douglasii in that FNA attributes P. douglasii ssp. johnstonii to P. sawatchense ssp. oblivium. Kartesz 1999 maintains subspecies johnstonii in P. douglasii." (Marta Donovan, personal communication, 2010). |
Species Information
General:
Annual herb from a small taproot; stems ascending to erect, numerous, simple to freely branched, 10-40 cm tall.
Leaves:
Basal leaves lacking; stem leaves alternate, linear to narrowly oblong, egg-shaped or elliptic, the blades 1-8 cm long, unstalked or nearly so, sometimes reduced to bracts above; stipules short-sheathing, 5-12 mm long, clear, becoming ragged.
Flowers:
Inflorescence of few flowers in elongate axillary racemes; perianths 1.5-5 mm long, greenish with white or pinkish margins, 5-lobed nearly to the base.
Fruits:
Achenes, lanceolate to egg-shaped, sometimes 3-angled, black, smooth and shiny, 2-4 mm long.
Ecology
The table below shows the species-specific information calculated from
original data (BEC database) provided by the BC Ministry of Forests and Range.
(Updated August, 2013)
| Site Information |
Value / Class |
||
|
Avg |
Min |
Max |
|
| Elevation
(metres) |
1120 | 304 | 2013 |
| Slope
Gradient (%) |
39 | 0 | 360 |
|
Aspect (degrees) |
197 | 0 | 360 |
| Soil
Moisture Regime (SMR) [0 - very xeric; 4 - mesic; 8 - hydric] |
1 | 0 | 6 |
| Modal
Nutrient Regime
Class |
B | ||
| #
of field plots species was recorded in: |
308 | ||
| Modal
BEC Zone Class |
IDF | ||
|
All BEC Zones (# of stations/zone) species was recorded in |
AT(7), BG(46), CWH(1), ESSF(50), ICH(25), IDF(73), MS(57), PP(31), SBPS(1), SBS(10) | ||
|
Source:
Klinkenberg 2013
|
|||
Habitat and Range
Moist to dry rocky slopes and disturbed sites in the lowland and montane zones; frequent in SC BC and on Vancouver Island, rare elsewhere in BC; E to PQ and S to NY, UT, NM and CA.Status Information
Synonyms
Synonyms and Alternate Names:
Polygonum douglasii var. austiniae (Greene) M.E. Jones