In a replicated study conducted from 1990 to 1992, cover crops and a control (resident vegetation) were evaluated in an organic wine-grape vineyard (cv. ‘Chardonnay’), located at a valley floor site in Hopland, Mendocino County, California. The purpose was to assess plant phenology, stature, biomass production, competitiveness with resident vegetation, and second-year stand regeneration or persistence in an unfilled vineyard. Legumes (Fabaceae) evaluated included nine annual and two perennial types of clover (Trifoliumspp.), bell bean and three other types ofVicia, two types of coolseason annual medic (Medicagospp.), field pea (Pisum sativumssp.arvense), a mixture of biennial sweetclovers (Melilotus albaandM. officinalis), broadleaf birdsfoot trefoil (Lotus comiculatus). There were six types of cool-season annual grasses (Poaceae) including three cereal grains. Native Californian perennial grasses included one rhizomatous and five bunch types. The sole representative of Brassicaceae was black mustard (Brassica nigra). Unseeded, resident vegetation plots served as a control.