The habitats where knotgrass~(Polygonum aviculare) grows:

Arable
Brownfield
Coastal floodplain grazing marsh
Coastal vegetated shingle
Gateways and tracks
Hard cliff and cliff slope
Lowland fen
Only East Anglia
Open habitat arable weed fertile loam and clay
Open habitat arable weed less fertile acid
Open habitat arable weed light lime rich
Pond ditch and canal
Salt marsh