Definition - What does Weed mean?
In the context of viticulture, a weed is any plant that grows in the vineyard and competes for water and soil nutrients with wine grape vines. Weed management must be taken seriously by viticulturists, as an overgrowth of weeds can affect the vines ability to mature properly and bear fruit.
WineFrog explains Weed
Wine grape vines need to be protected from an overgrowth of weeds to ensure proper growth and health. A weed is defined by being a plant in an undesirable location in the vineyard; for instance, if it is too close to the vine and competes for resources, not just the type of plant that it is. When weeds grow in the vineyard they compete with vines for water and nutrients. They can also host insects and diseases that can harm the vine as well as provide shelter for rodents.
Weeds can also interfere with irrigation, by limiting water disbursement to the vine. Common and hard to control weeds in the vineyard are grasses like Bermuda and Johnson grass and annuals like Willow Herb, Mustard and Horse Weed, which compete with the vines during their most vigorous growth and development. These common weeds can be introduced by seed through irrigation, or fertilizer/manure or even be spread through the air. While controlling weeds is important when vines are young, they must be managed throughout the vineyard on a consistent basis to avoid ongoing problems.
The use of systemic or contact herbicides can assist in this effort.