What herbicides can I use in the vegetable garden?

Question:

What herbicides can I use in the vegetable garden?

Answer:

Many home gardeners choose to avoid the use of herbicides in vegetable gardens since they are growing edible crops.  In certain situations, however, a gardener can use herbicides to supplement other weed control strategies.  Most herbicides are not labeled for use in a vegetable garden.  Be sure to consult the product label before any application.

Pre-emergent herbicides

Pre-emergent herbicides are used to prevent weed seeds from completing the germination process.  They have limited use in the vegetable garden because they will also prevent germination and growth of those vegetable crops that are direct sown in the garden such as beans, lettuce, corn, and others.  If only vegetable transplants are used, pre-emergent herbicides can help reduce annual weeds but the timing is important.  Herbicides with the active ingredient trifluralin are available to home gardeners and can be used in certain situations.  Consult the label to apply these herbicides at the appropriate time and frequency to control weeds and not impact the germination of future seed-driven vegetable crops.

Post-emergent herbicides

Post-emergent herbicides are used to kill weeds that have already begun growing.  They must be carefully applied as they have a high potential to harm both weeds and crops.  Always apply herbicides when winds are calm and temperatures are cool to prevent drift and damage to desirable plants.  Protect nearby plants with barriers like buckets, tarps, or boxes to further reduce problems with drift.  Herbicides can also be applied with a sponge and wiped onto the leaves of the weed to prevent collateral damage to nearby plants. Non-selective herbicides with the active ingredient glyphosate are available to home gardeners and can be used in certain situations.  Herbicides must be used according to the label instructions on the package. Failure to follow directions may kill desirable plants or prevent other plants from being grown in the area.

Organic Herbicides

Organic herbicides can also be effective and all of them act as non-selective herbicides. Many organic herbicides use one or more of the following active ingredients: acetic acid, citric acid, clove oil, lemongrass oil, d-limonene, and ammonium nonanoate, among others. 

Most organic herbicides work as contact herbicides, killing the leaves and stems, but not being translocated to other parts of the plants, such as roots. Often, multiple applications every two to three weeks are needed for complete control. Organic herbicides are more effective on younger, smaller weeds. Always follow the label directions on all herbicides. Even organic herbicides can harm desirable plants or people when used inappropriately.

More information about using herbicides in the vegetable garden can be found in this article: Weed Control in the Vegetable Garden