Seasonal dynamics of weed vegetation and their response to tilling and mulching were studied in a vineyard in the south-eastern part of the Czech Republic. The objective of the study was to determine shifts in the diversity of weed vegetation, associated with the transition from intensive agricultural management with frequent tilling and herbiciding, to a more environment-friendly management by mulching. Vegetation was studied in permanent plots of 1 x 1 m. First sampling was done in 1994, when even lanes, between the rows of grapevine, were still tilled while mulching was newly introduced in odd lanes. After the entire vineyard had been converted into mulching in 1995, permanent plots were re-sampled in 1999 and 2000. The plots were repeatedly sampled 5 to 7 times a year. In this way, three variants could be compared, including tilling, recently introduced mulching, and mulching lasting for 4x6 years. Redundancy analysis and variance partitioning showed that 49.5% of the variation in species composition could be explained by management and 22.6% by seasonal changes. Mulching led to increased species richness and to an increased proportion of hemicryptophytes at the expense of therophytes. Species associated with particular management types and particular seasons were determined.