Common Fieldcap vs Common knotweed

Agrocybe pediades compared with Polygonum plebeium

Key Differences

• Common Fieldcap is Least Concern while Common knotweed is Not Evaluated.

Taxonomic Classification

Rank	Common Fieldcap	Common knotweed
Kingdom	Fungi (Fungi)	Plantae (Plants)
Phylum	Basidiomycota (Club Fungi)	Magnoliophyta (Flowering Plants)
Class	Agaricomycetes (Mushrooms)	Magnoliopsida (Dicots)
Order	Agaricales (Gilled Mushrooms)	Caryophyllales (Caryophyllales)
Family	Strophariaceae	Polygonaceae
Genus	Agrocybe	Polygonum
Species	Agrocybe pediades	Polygonum plebeium

Conservation Status

Common Fieldcap

LC — Least Concern

Common knotweed

NE — Not Evaluated

Physical Characteristics

Attribute	Common Fieldcap	Common knotweed
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Common Fieldcap

Habitat

Typically found in forest floors, decomposing wood, and soil ecosystems.

Range

Found across Europe (5 countries) and North America (United States).

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).

Common Fieldcap

The Common Fieldcap (<em>Agrocybe pediades</em>) is a saprotrophic fungus belonging to the genus Agrocybe within the family Strophariaceae. It typically produces small, tan to pale brown cap-shaped fruiting bodies and is often found growing in clusters or scattered on lawns, grassy areas, forest floors, decomposing wood, and soil-rich ecosystems. The species typically inhabits forest floors, decomposing wood, and soil ecosystems, obtaining nutrients by breaking down dead organic matter. Its geographic range includes several European countries — Belgium, Denmark, Norway, Portugal, and Sweden — as well as the United States in North America. <em>Agrocybe pediades</em> is assessed as Least Concern on the IUCN Red List, reflecting its broad distribution and apparent stability. Biological traits of this species, including specific data on fruiting body size, lifespan, and ecological preferences, remain poorly documented in the scientific literature. Like other members of its genus, it typically fruits during warmer months and often appears after rainfall in nutrient-rich grassland and woodland habitats.

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 3 countries:

🇧🇪 Belgium 🇸🇪 Sweden 🇺🇸 United States