The roots of grass and weeds can crowd out grape vines at the root. Grass and weeds also compete with the vines for moisture and nutrients. Before reaching for a chemical weed killer, think again. Some weed killers such as 2,4-D can have negative affects on your grapes. Even if you are careful not to get weed killer on the vines, the fumes can deform leaves, destroy flower clusters and prevent grapes from forming. A more effective solution is to combine good management practices with mechanical weed blockers.
Kill any residual weeds and weed seeds in the vineyard before planting grape seeds by watering the weeds and placing clear plastic over the soil. This process, known as solarization, will literally cook the weeds.
Uproot grass and weeds by cultivating the soil every 2 to 3 weeks. Work a rototiller over the spaces between the rows where grass may grow. Install shallow tines on the rototiller so as not to disturb the roots.
Mulch smaller vineyards by spreading a layer of sawdust, well-rotted manure, hay or shredded newspaper with a pitchfork to keep weeds under control. Mulch prevents weeds by blocking sunlight to the soil and prevents weed seeds from sprouting.