The trailing nature of the plant prevents proper crop development. The clinging bristles make crop handling and harvesting difficult. Because there is so much green material at harvest, straight combining becomes difficult, if not impossible. The seeds are similar in size and shape to canola, making them a serious contaminant of canola and rapeseed, resulting in the downgrading of these crops.
Cleavers can be very competitive, causing significant yield losses. The trailing plants also interfere with harvesting equipment. It is a serious contaminant of canola seed, lowering seed quality.
Take a minimum of 20 weed counts across the field. Check low spots for patches. Scout fields early because the weed is most sensitive to herbicides in its early growth stages.
Effects On Crop Quality
Winter annual cleavers should be controlled in the fall after germination with tillage or a herbicide.
When mature, the stems are square, with short, bristly downward pointing hooks growing on corners, generally 60-120 cm (2-4 ft.) long and trailing. The leaves are in whorls, in groups of 6-8. They are pointed at the tip, roughened, and 2.5-7.5 cm (1-3 in.) long. The flowers are white, small, and produced in the axils of upper leaves.
The weed competes for light and nutrients. Heavy infestations can cause yield losses. Cleavers at densities of 100 plants per square metre (sq. yd.) can cause a 20% yield reduction in canola.
Use certified seed that is free of cleavers. All grades of pedigreed seed must be free from cleavers seed. Clean tillage and harvesting equipment before changing fields.
Cleavers may have been introduced to North America in grain fields by early settlers who imported contaminated seed from Eurasia (Malik and Vanden Born 1988 Footnote 2 ). It can also be transported by harvesting equipment and animals (Ministry of Agriculture, Food, and Fisheries 2002 Footnote 7 ).
Secondary Noxious, Class 3 in the Canadian Weed Seeds Order, 2016 under the Seeds Act.
Arable land, particularly grain fields, fence rows, barnyards and pastures. Also found in deciduous woods, thickets and rocky coastal bluffs, parklands, shores and waste ground (Malik and Vanden Born 1988 Footnote 2 , Darbyshire 2003 Footnote 6 ). Thrives in moist, well drained habitats, in loam and sandy loam soils (Malik and Vanden Born 1988 Footnote 2 ).
Habitat and Crop Association
Malik, N. and Vanden Born, W. H. 1988. The biology of Canadian weeds. 86. Galium aparine L. and Galium spuium L. Canadian Journal of Plant Science 68: 481-499.
Worldwide: Native to Eurasia and North America and widely naturalized, found in temperate zones throughout the world and at higher altitudes in the tropics (Malik and Vanden Born 1988 Footnote 2 , CABI 2016 Footnote 3 , USDA -ARS 2016 Footnote 4 ). Occurs throughout North America from Alaska to the east coast (Malik and Vanden Born 1988 Footnote 2 , CABI 2016 Footnote 3 , USDA -NRCS 2016 Footnote 5 ), with both native and introduced populations present in Canada (Brouillet et al. 2016 Footnote 1 ).
A single plant can produce up to 3,500 seeds that remain viable for up to 6 years in the soil (Ministry of Agriculture, Food, and Fisheries 2002 Footnote 7 ). The spiny-hooked fruit is adapted to animal dispersal (Malik and Vanden Born 1988 Footnote 2 ).
Brouillet, L., Coursol, F., Favreau, M. and Anions, M. 2016. VASCAN, the database vascular plants of Canada, http://data.canadensys.net/vascan/ [2016, May 30].