Grass Control for Watermelons

Non-Selective Herbicide

• A weed-free planting site is imperative before planting watermelons. Grass weeds compete with watermelon seedlings and reduce their vigor. To remove weeds from the planting area, spray the entire planting area with a non-selective herbicide, but be careful around the turf grass and desired plants. This herbicide will kill anything that the spray comes in contact with. Till the area to remove the dead weed debris.

Pre-Emergent Herbicide

• Apply a pre-emergent herbicide that contains the active ingredient bensulide after the watermelon seedlings have emerged. This herbicide prevents grassy weed seed germination by creating a barrier in the soil. Once the weed seedlings emerge, they come into contact with the herbicide and die. Spray the entire watermelon area and cover the planting area evenly to prevent germination. Water the pre-emergent herbicide so it sinks into the soil.

Post-Emergent Herbicide

• Post-emergent herbicides that contain sethoxydim or clethodim can be used on existing grassy weeds in watermelon planting areas. When plant foliage absorbs the spray, their ability to photosynthesize, create proteins or grow roots become interrupted. It is best to spray young grassy weeds for effective weed control as mature grassy weeds may take several herbicide applications. Tall grassy weeds may be controlled with a herbicide that contains glyphosate. Apply this herbicide by spraying a rag, then wrapping the rag over a rake and spraying the tops of the weeds.

Cultural Management Strategies

• Gardeners who do not want to use herbicides around their watermelon crops can employ cultural management practices by pulling the weeds as they grow. Pull weeds by hand throughout the growing season to reduce the amount of reserve energy stored in perennial weed roots. Also, mulching around the watermelon crops will prevent annual weed seeds from germinating. Plastic mulch with drop irrigation is commonly used to prevent weed growth.