On six “Organic Pilot Farms in North Rhine-Westfalia” and on the Experimental Farm Wiesengut in Hennef, oil radish, white mustard, buckwheat and oats were under-seeded in potato stands in order to control weed infestation after senescence of potato shoots. Different sowing dates were tested. In all field trials underseeds suppressed weed growth significantly. Weed dry matter as well as the density and length of Che-nopodium album were reduced mainly by oil radish and early sowing combined with the last mechanical treatment (ridging). Buckwheat able to suppress weed growth effi-ciently is suggested to be used in vegetable production
