and Wien (1983) screened turfgrasses and clovers to find less competitive mulches for sweet corn and cabbage. Weed suppression is one of several benefits achieved by includingA third way to avoid or decrease the competition in a cover crop in a cropping system. A requirement for developing cover crop systems is to find species and cultivars which are adapted such systems is to intercrop a main crop and a cover for the local climate and latitude, prevent weed infestation, and do crop with a synchronized onset of maximum vegetative not compete with the main crop. Two experimental series were estabgrowth. This synchronization of cover crop and main lished at three locations in Norway to evaluate the ability of different crop could be achieved in different ways. Mü ller-Schä rer species for use as cover crops in vegetable production. The first series and Potter (1991) concluded that cover plants should of experiments was with subclover (Trifolium subterraneum L.) cultibe seeded to emerge in the middle of the vegetation vars sown at different dates throughout the summer and the second period of the main crop, e.g., in field-planted leek (Alwith different winter annual legume species sown in late summer. lium porrum L.). De Haan et al. (1994) have studied Winter hardiness, life cycle, growth characteristics, and weed suppresthe opposite way to avoid interference problems in sion ability of winter annual legumes sown in the autumn were studied. The experiments showed the following ranking of winter hardiness: cover crop systems in the north central region of the hairy vetch (Vicia villosa Roth.) (best), black medic (Medicago lupu-USA. They tried to develop a spring seeded smother lina L.), crimson clover (Trifolium incarnatum L.), and subclover plant that had been selected for its ability to suppress (poorest). Time of flowering and senescence, factors related to compeweeds without affecting crop yield. This cover crop flowtition in cover crop systems, showed that subclover was the most ered 3 wk after emergence and began senescence 5 wk promising species followed by crimson clover and hairy vetch-black after emergence (D.L.Wyse, personal communication). medic. The winter annual legume species showed the ability for naturalAnother approach suggested by Ilnicki and Enache reestablishment in the second autumn. Hairy vetch showed the highest (1992) was to use winter annual legumes, e.g., subclover biomass production, the lowest regrowth ability after mowing, and as living mulch. Winter annual legumes sown in late