Vineyard Weed Control

Competition from weed or cover crop growth has a substantial effect on vine growth, fruit yield and quality.


Williamson Vineyards Weed Control

For weed control we use mechanical implements such as rotary disks rather than use herbicide products. Our research on this is reflected in our vineyard management protocols. Here is a synopsis:

  • Minimizing weed competition under the vines is critical to successful vine growth and development.

  • Actively growing cover crops, including legumes, between bloom and veraison can reduce vine size and fruit yield resulting in higher quality fruit so effective mechanical weed control is financially viable.

  • Vine size and fruit yield increase proportionally to the width of the weed-free band under the vines providing another benefit for the investment in mechanical weed control.

Our vineyard rows are typically seven feet in width with plants four feet apart. Herbicides are not used in the rows because we grow cover crops there which are returned to the soil to provide natural nutrients and nitrogen, while helping control over-vigorous vine growth.


Using Herbicides

The use of herbicides like Glyphosate, as well as all conventional and organic pesticides in commercial operations, require licensing from the State of California Department of Pesticide Regulation. The county Agricultural Commissioner’s office regularly inspects applicators, handlers and businesses to ensure that all health and safety conditions are met for storage and application. It is illegal to use any pesticide (conventional or organic) in a manner that would violate the labeled rules set forth by the U.S. EPA and Cal EPA

Rather than use a commercial herbicide we would try an organic method such as a mixture of 5% agricultural vinegar (acetic acid) and dish soap. Weed management usually takes place in the Spring season when the vines are still dormant and have no leaves.

If we ever did use a herbicide the use would be minimal, spot-sprayed on individual invasive weeds and manually applied with a controlled, low-pressure applicator with enclosed flat fan nozzles to prevent the possibility of spray being spread by the wind,

After application a herbicide dissipates within a few days. With such a short residual period the herbicide applied sparingly generally has little or no soil residual. It is never sprayed on the vines because it would kill them as well, hence not having absorbed any herbicide they cannot pass it on to their grapes or the wine.


About Glyphosate Herbicides

Glyphosate is a systemic herbicide that, when applied at the proper time, kills the entire weed including the roots. Glyphosate also can cause damage to grapevines if grape leaves are contacted, and the risk of damage increases as the season progresses.

Roundup® (a trade name used by Monsanto) and other herbicides based on glyphosate are probably the most commonly applied weed killers in use today. These herbicides are used by everyone from farmers to foresters to gardeners to biologists trying to control invasive exotic plants.

The acute oral toxicity for humans is low, having an oral toxicity similar to vitamin A and less toxic than aspirin however controversy has arisen because of a false-advertising lawsuit against Montsanto’s Roundup which never went to trial.

The World Health Organization surveyed third party research on glyphosate and cancer links and concluded the herbicide is “probably carcinogenic to humans.”

The EPA re-evaluated the data and re-classified glyphosate as a Group E chemical, indicating that there was no evidence that glyphosate herbicides like Roundup causes cancer in humans.

Glyphosate-based herbicides are sprayed on the leaves of weeds to inhibit a specific enzyme that the weeds need in order to grow. Unable to produce proteins essential to growth, they yellow and die over the course of several days.






Rotary Disk Weed Control

Rotary Mower Vineyard Weed Control









Low-Pressure Spot Spray & Fan Nozzle

Manual Herbicide Spray





We Never Use These Methods






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