How to Apply Pre-Emergent in a Vegetable Garden

Apply mulch to the weeded vegetable garden. A 2- to 4-inch covering of organic mulch keeps weed seeds shaded, deterring germination. Weeds that don’t germinate can’t grow to become a nuisance. Mulch also retains water and keeps roots cool in hot summer temperatures.

Plant large-leafed vegetables to shade out weed seeds. Plant weed-free seeds or vegetable transplants closely, into a weeded garden bed, allowing room for root development. North Carolina State University includes squash, pumpkins and corn on their list of shade-creating vegetables. Encourage rapid growth of the shade providers by planting them in proper sunlight and giving them enough water. Densely planted vegetables leave less room in the garden for weed germination and growth.

Spray or scatter organic pre-emergent controls containing corn gluten meal. This ingredient stops most seed germination. Containing a 10 percent rate of nitrogen, corn gluten encourages green, leafy growth of vegetable plants. Corn gluten products come in spray or pelleted forms. These products are not designed to kill existing weeds. Corn gluten also stops germination of desired seeds, so don’t apply it until your vegetable seeds have leaves and are actively growing.

Resort to chemical controls when necessary. Most chemical pre-emergent weed controls contain the active ingredient trifluralin (Treflan). As with corn gluten products, trifluralin is available in spray and granular form, and as a wettable powder. The label indicates trifluralin should not be used on or near garlic, lettuce, cucumbers, onions, squash or melons. Don’t spray on windy days, as drift from the chemical may damage neighboring crops and ornamentals.