How to Kill Sedge Grass in a Vegetable Garden

Monitor landscape fabric for tears during the growing season.

Sedges differ from grasses by the thickness of their leaves and roundness of the tips of the blades. It is important for gardeners to remove sedges from their vegetable gardeners to eliminate hospitable environments for insects and diseases. Furthermore, sedges such as purple and yellow nutsedge use up the soil's nutrients and moisture meant for vegetable plants. Because vegetable plants are sensitive to herbicides, gardeners must choose proper cultural and chemical methods for removing sedges.

Things You'll Need

• Herbicide
• Landscape fabric
• Landscape pins
• Mulch

Instructions

1. Apply an herbicide to the sedge growing in the vegetable garden in the early spring right before planting vegetable transplants and seeds. Use a broad spectrum herbicide that contains glyphosate. Glyphosate leaves little toxic residue that could harm vegetable plants. Wait 10 days to reapply or to plant.

2. Spray a pre-emergent herbicide to prevent yellow nutsedge from germinating after planting your vegetable plants. Wait for vegetable plant seeds to sprout before applying the pre-emergent herbicide, because some pre-emergent herbicides prevent vegetable seed germination. Use a pre-emergent herbicide that contains the active ingredient dichlobenil. Unfortunately, there are no pre-emergent herbicides available to control purple nutsedge. Dilute the herbicide in a sprayer. Evenly apply the herbicide to the vegetable garden area.

3. Water the vegetable garden with 1 inch of water to encourage the chemicals to form a barrier in the soil.

4. Lay a piece of landscape fabric down over the vegetable garden. Landscape fabric works by reducing sunlight for sedge growth and generating enough heat to kill seeds. Cut the fabric to fit the area. Make X-shaped cuts in the fabric to pull down over plants. Secure the fabric using landscape pins every 6 inches around the perimeter.

5. Spread a 3 to 4 inch layer of mulch over the top of the landscape fabric to increase the heat and further smother sedge plants..

6. Cut the top of any sedge growing through openings in the landscape fabric and mulch. By cutting the top of the sedge growth, you will deprive the plant of some of the stored energy it uses to produce more plants. Continually cutting the sedge causes it to use up its reserve energy and eventually the sedge will stop sprouting.

Tips & Warnings

• Apply a non-selective herbicide that contains pelargonic acid around vegetable plants to kill existing sedge plants. Focus the spray on the foliage of the weed to prevent herbicide drift to vegetable plants.

References

• University of California, Davis, Integrated Pest Management; Nutsedge Management Guidelines; March 2010
• Texas Gardener; Weed Wars; Skip Ritcher
• Clemson University Extension; Nutsedge; Karen Russ