BC Conservation Data Centre: Species Summary
Polygonum austiniae
Austin's knotweed
| Scientific Name: | Polygonum austiniae Greene | ||||||||||
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| Scientific Name Synonyms: |
Polygonum douglasii ssp. austiniae
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| English Name: | Austin's knotweed | ||||||||||
| Classification / Taxonomy | |||||||||||
| Scientific Name - Concept Reference: | Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR. | ||||||||||
| Classification Level: | Species | ||||||||||
| Taxonomy Comments: | Formerly tracked as P. douglasii ssp. austiniae. Elevated to full species in Oct. 2006. | ||||||||||
| Species Group: | Vascular Plant | ||||||||||
| Species Code: | POLYAUS | ||||||||||
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| Conservation Status / Legal Designation | |||||||||||
| Global Status: | G5T4 (Dec 2025) | ||||||||||
| Provincial Status: | S2 (Apr 2019) | ||||||||||
| BC List: | Red | ||||||||||
| Provincial FRPA list: | |||||||||||
| Provincial Wildlife Act: | |||||||||||
| COSEWIC Status: | |||||||||||
| SARA Schedule: | |||||||||||
| General Status Canada: | 3 - Sensitive (2010) | ||||||||||
| Ecology & Life History | |||||||||||
| General Description: | Austin's Knotweed is a sparsely hairy annual with erect stems that are 3-10 cm high and branched near their bases. The alternate, narrowly egg-shaped to elliptic leaves are 5-15 mm long and 1/2-1/3 as wide. The lower leaves have short petioles, while the upper leaves are sessile and smaller. There are small membranous sheaths, or stipules, surrounding the stem at the point of leaf attachment. Groups of 1-4 tiny, nodding flowers occur in the axils of all but the lowest leaves. Each flower has 5-8 stamens and 5 petal-like tepals that are 2-3 mm long and green with white or pink margins. The shiny black achenes are 3-sided and mostly 2-2.5 mm long. | ||||||||||
| Technical Description: | |||||||||||
| Diagnostic Characteristics: | There are many similar-appearing annual species of POLYGONUM. The typical P. DOUGLASII has leaves that are less than 1/3 as wide as they are long and achenes that are ca. 3 mm long. Many other species of POLYGONUM have erect flowers. A technical key and hand lens may be required for positive determination. | ||||||||||
| Similar Species: | |||||||||||
| Habitats: (Type / Subtype / Dependence) |
Forest / Conifer Forest - Dry / Facultative - occasional use
Rock/Sparsely Vegetated Rock / Rock/Sparsely Vegetated Rock / Facultative - frequent use |
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| Provincial Phenology: (1st half of month/ 2nd half of month) |
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| Elevation (m) (min / max): | Provincial: | ||||||||||
| Known Pests: | |||||||||||
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| Dispersal: | |||||||||||
| Provincial Inventory | |||||||||||
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| Ownership of occurrences (Known locations): | |||||||||||
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| Economic Attributes | |||||||||||
| Distribution | |||||||||||
| Endemic: | N | ||||||||||
| Disjunct, more common elsewhere: | |||||||||||
| Peripheral, major distribution elsewhere: | |||||||||||
| Authors / Contributors | |||||||||||
| Global Information Author: | MZB | ||||||||||
| Last Updated: | Dec 23, 1996 | ||||||||||
| Provincial Information Author: | |||||||||||
| Last Updated: | |||||||||||
| Last Literature Search: | |||||||||||
| References and Related Literature | |||||||||||
Douglas, G.W., D. Meidinger, and J. Penny. 2002. Rare Native Vascular Plants of British Columbia, 2nd ed. B.C. Conserv. Data Centre, Terrestrial Inf. Branch, Victoria. 358pp. |
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Douglas, G.W., D. Meidinger, and J. Pojar, eds. 1999. Illustrated Flora of British Columbia, Vol. 4, Dicotyledons (Orobanchaceae through Rubiaceae). B.C. Minist. Environ., Lands and Parks, and B.C. Minist. For., Victoria. 427pp. |
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Flora of North America Editorial Committee (FNA). 2005. Flora of North America north of Mexico. Vol. 5. Magnoliophyta: Caryophyllidae: Caryophyllales, Polygonales, and Plumbaginales. Oxford Univ. Press, New York. vii + 656 pp. |
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Poole, J. M. and B. L. Heidel. 1993a. Sensitive plant surveys in the Big Belt and Elkhorn Mountains, Helena National Forest, Montana. Unpublished report to the Helena National Forest. Montana Natural Heritage Program. Helena, MT. 129 pp. plus printouts, maps. |
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Vanderhorst, J. and B. L. Heidel. 1995. Sensitive plant survey in the Tobacco Root Mountains, Madison County, Montana. Unpublished report to the Beaverhead and Deerlodge National Forests. Montana Natural Heritage Program. Helena, MT. 66 pp. plus appendices. |
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Please visit the website Conservation Status Ranks for definitions of the data fields used in this summary report.
Suggested Citation:
B.C. Conservation Data Centre. 1996. Species Summary: Polygonum austiniae. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 14, 2026).