Planteværn Online > Skadevoldere - Weed biology<br> <sub>Agro-region: Denmark</sub> - Knotgrass
Crop Protection Online    
5.12 2022 undefined

Weed biology
Agro-region: Denmark

Knotgrass Previous page Next page

Go to identification key for weeds

Can be mistaken for

Ribwort Plantain, which has somewhat larger dicotyledon leaves and true leaves.


Long and slender with entire leaf margins. Unstalked. The surface is sometimes slightly hairy, otherwise smooth. Length approx. 10-15 mm.

True leaves
Lancet-shaped with entire leaf margins. Unstalked. The surface is sometimes slightly hairy, otherwise smooth. The colour of the first true leaves is often very reddish. Length approx. 20-30 mm.

Mature plant
Knotgrass is a low-growing plant with 20-60 cm long, trailing stems. The species is known by the membraneous sheaths (“cones”), which encircle the stems and which are located at each attachment. The diameter of the flower is approx. 2 mm. Seed production: Up to approx. 200 seeds per plant.

Almost triangular with a slender, slightly curved top. Triangular cross section. Slightly granular surface. The seed is usually surrounded by remnants of the perianth. Thousand grain weight approx. 2.7 g.


Propagation and dispersal
Only through seeds.

Summer annual.


The species is a very common weed in spring-sown crops throughout Denmark. In cereal crops and Oil-seed Rape the plant does not have any special influence on yield. However, it can easily become very troublesome in open crops.

For treatment options, consult 'Herbicides Across'.
For more options, consult 'Main Menu'.



Names in different languages

Danish : Pileurt, vej
German : Vogelknöterich
English : Knotgrass
Latin : Polygonum aviculare L.
Norwegian : Tungras
Swedish : Trampört

Knotgrass: Seedling
Knotgrass: Early stage
Early stage
Knotgrass: Flower
Knotgrass: Mature plant
Mature plant
Knotgrass: Seeds

Crop Protection Online is published by Department of Agroecology, Aarhus University and SEGES Innovation.
Informations for which license is not needed may be used with reference of source.

E-mail to