Nigel Cattlin / Common knotgrass (Polygonum aviculare) growing as arable weed. England, UK. August.

Nick Upton / Knotgrass (Polygonum aviculare) flowering in damp grassland, Cornwall, UK, September.

Konstantin Mikhailov / {Polygonum aviculare} flowering, Lake Baikal, Siberia, Russia

Nigel Cattlin / Prostrate knotgrass (Polygonum aviculare) plants growing in a young Sugar beet (Beta vulgaris) crop, England, UK. June

Paul Harcourt Davies / Alpine bistort ( (Polygonum aviculare). Col di Rodlea, Campitello di Fassa, Dolomites, Trentino, Italy. June.

Paul Harcourt Davies / Alpine bistort ( (Polygonum aviculare). Col di Rodlea, Campitello di Fassa, Dolomites, Trentino, Italy. July.

Linda Pitkin / Knotgrass (Polygonum aviculare) Ranscombe Farm Nature Reserve, Kent, England, July.

Nigel Cattlin / Severe infestation of several broad-leaved weed species in a young wheat crop, Cambridgeshire, England, UK,