Abstract: The plant species richness of vineyard inter-row groundcover can maintainbiodiversity of plants and arthropods, and could improve conservation biocontrol by reducingpest insect pressure. Five different seed mixtures were tested during two years on a Bordeauxvineyard plot Château Les Vergnes (Gironde, France). The initial plant composition and itsevolution over time were studied in 2009 (first year after 2008 autumn sowing) and 2010 throughexhaustive botanical monitoring during the growing season (April-July). Large differences wereobserved in plant species composition and abundance, even though the existing seed bank seemsof major influence on the species richness. The farmers’ management of the plot (mowing,machine passing) shows a strong selection pressure on the plant species present in the seedmixtures.