There is an increasing interest in the use of cover crops in agriculture, inSweden mainly for the use as catch crops to reduce nitrogen leakage. Some ofthese crops are known for their allelopathic abilities, which may play arole in the control of weeds and contribute to reduced herbicide use. Thisstudy aimed to explore the possible suppressive effect of the cover cropspecies white mustard, fodder radish, rye, and annual ryegrass on the earlygrowth of the weed species silky windgrass, shepherd's-purse, and scentlessfalse mayweed. In a greenhouse experiment using fresh cover crop residues,white mustard was the only crop that showed an effect. It reduced bothseedling establishment, by 51 to 73%, and biomass, by 59 to 86%, ofshepherd's-purse and scentless false mayweed. In contrast, in a growthchamber experiment using frozen material, mean germination time of silkywindgrass was extended by 20 to 66% by all cover crops. Also, three out offour cover crops reduced root growth in scentless false mayweed by 40 to46%, and two out of four cover crops reduced root growth in shepherd's-purseby 13 to 61%. However, considering seedling survival, white mustard was themost prominent cover crop, reducing survival by 21 to 57% inshepherd's-purse and scentless false mayweed. In this paper we provideevidence that different weed species show different response to differentcover crops under climatic conditions prevailing in Scandinavia. Suchresults emphasize the importance of understanding weed–cover cropinteractions as necessary for developing cropping systems that can utilizecover crops to suppress local weed flora.