Weed Management in Oil and Fibre Crops

Oil Seed Rape: in organic crops broad-leaved weeds are considered to be less of a problem than wild oats and blackgrass. In a survey of conventional winter oilseed rape in central southern England in 1985 cleavers was the most frequent weed being found in 57% of fields whilst common poppy, prickly sowthistle (Sonchus asper) and scentless mayweed (Tripleurospermum inodorum) were also common (21, 18 and 14% of fields respectively). Volunteer barley can have a severe effect in the autumn on the growth of winter oilseed rape and, in Canada, it has been shown that increasing the seed rate improves crop yield when volunteer barley is a problem but there is no advantage when the crop is weed-free.

Linseed/ Flax: the crop is not competitive and cannot compete against common chickweed, charlock, wild oats and other quick growing annuals. Fields should be free of perennial weeds. Experiments to determine the competitive effects of weeds on spring-sown linseed found wild oat (Avena fatua) and knotgrass (Polygonum aviculare) to be highly competitive. Chickweed (Stellaria media) and fat-hen (Chenopodium album) were less damaging. Chickweed formed a low mat that did not affect the crop growth while the fat-hen did not become as vigorous as it does in many crops. In winter linseed, chickweed and cleavers could be left in the crop until March-April without seriously jeopardising yields. Flax cultivars differ in their susceptibility to the allelochemicals produced by wild oats and some other weeds.

Hemp: there is time before drilling in late April to prepare a stale seedbed. Once the crop is established the foliage is dense and suppresses weeds, minimising further weed control needs. Weed free crop material is essential for processing.

For more details on weed management in Oil and Fibre Crops please download our outline (48Kb pdf file).

Further information:


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