Common knotweed vs Red-knotgrass

Polygonum plebeium compared with Polygonum patulum

Taxonomic Classification

Rank	Common knotweed	Red-knotgrass
Kingdom same	Plantae (Plants)	Plantae (Plants)
Phylum same	Magnoliophyta (Flowering Plants)	Magnoliophyta (Flowering Plants)
Class same	Magnoliopsida (Dicots)	Magnoliopsida (Dicots)
Order same	Caryophyllales (Caryophyllales)	Caryophyllales (Caryophyllales)
Family same	Polygonaceae	Polygonaceae
Genus same	Polygonum	Polygonum
Species	Polygonum plebeium	Polygonum patulum

Evolutionary Relationship

Common knotweed and Red-knotgrass share a common ancestor at the Genus level: Polygonum.

Conservation Status

Common knotweed

NE — Not Evaluated

Red-knotgrass

NE — Not Evaluated

Physical Characteristics

Attribute	Common knotweed	Red-knotgrass
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Common knotweed

Habitat

Typically found in diverse terrestrial habitats from tropical forests to temperate regions.

Range

Widely distributed across Africa (Madagascar), Asia (Japan, Taiwan), Europe (5 countries), and North America (United States).

Red-knotgrass

Habitat

Typically found in diverse terrestrial habitats from tropical forests to temperate regions.

Range

Widely distributed across Europe (16 countries), North America (Canada, United States), Oceania and the Pacific (Australia), and South America (Colombia).

Common knotweed

Common Knotweed (<em>Polygonum plebeium</em>) is a low-growing annual herb in the family Polygonaceae, widely distributed across Africa, Asia, Europe, and North America. Its native range includes Madagascar in Africa, Japan and Taiwan in Asia, five European countries, and the United States in North America. The species typically inhabits diverse terrestrial environments including roadsides, cultivated fields, waste ground, and disturbed habitats, often thriving in compacted or trampled soils. It is a small, mat-forming plant with tiny pink or white flowers and narrow leaves, well adapted to anthropogenic landscapes. Its conservation status has not been formally evaluated by the IUCN. The broad distributional range and generalist habitat preferences of this species suggest resilience to moderate levels of disturbance, though its ecological role in native plant communities is less well characterized compared to its weedy occurrences in disturbed sites. Biological traits of this species remain poorly documented in the scientific literature.

Shared Countries

Both species can be found in 6 countries:

🇧🇪 Belgium 🇫🇷 France 🇳🇱 Netherlands 🇸🇪 Sweden 🇬🇧 United Kingdom 🇺🇸 United States