How to Rid Perennial Beds of Nut Grass

Dig deep to get out all the nut sedge's rhizomes.

Dig deep to get out all the nut sedge's rhizomes.

Although you may think of it as a grass, nut grass is botanically a bothersome sedge. Yellow nut sedge (Cyperus esculentus), which grows in U.S. Department of Agriculture plant hardiness zones 3 through 9, is a weed, and it requires the same growing conditions, nutrients and moisture as perennial flowers. If you want to remove the sedge from your perennial beds, both mechanical and chemical methods get the job done. The choice of which to use depends only on your preferences.

Know Your Nut Grass

A perennial, nut grass gets its name from the underground tubers it produces. These tubers, which look like nuts, grow on underground stems called rhizomes, and reach depths of 14 inches underground. New plant buds develop on the stems, popping up in your perennial bed. To identify nut grass, look for three long leafy bracts, or stems, at the base of the plant, or light brown flowers and seeds produced by the yellow variety.

Dig It Out

Mechanical removal includes hand pulling and digging, and it's a good idea to wear gloves to save your hands some wear and tear from the nut grass. To make the process easier, pull the plants when the soil is moist. You'll end up getting more of the root system, which prevents it sprouting again. Digging nut grass with a hoe or shovel removes the stem system more effectively, especially when the ground is dry and hard, and you might consider it a slightly easier process compared to hand pulling. After you remove the nut grass, check the bed for regrowth over the next couple of weeks, and pull or dig any new shoots as soon as possible to stay ahead of this aggressive plant.

Spraying Nut Grass

A postemergent herbicide, such as glyphosate, works as a spot treatment, soaking into the leaves and stems, and traveling through the root system, killing the entire plant. For nut grass application, a 1.5 percent mixture of 41 percent glyphosate works well. Mix 2 ounces of the herbicide with 1 gallon of water in a garden sprayer. Because glyphosate will kill any plant it touches, focus the spray nozzle to a fine stream before applying, so that it doesn't get onto your perennials. As an added precaution, wait until the wind dies down before you spray, so mist doesn't blow onto other plants, and consider covering nearby plants with plastic sheeting to protect them. Once you finish applying the herbicide, monitor the nut grass to make sure it's dying and apply the mixture again in seven days if it's still alive.

Keep It Away

A layer of mulch helps prevent the growth of nut grass, and you can choose a color and style to complement your perennials. A 2- to 3-inch layer of mulch controls weeds like nut sedge by blocking light, and has the added benefit of keeping the soil moist. Try to avoid piling mulch up near the stems of perennials, which can damage the plants. Instead thin the mulch out as you near the base of plants, stopping 3 to 4 inches away from the stems.

About the Author


Photo Credits

  • Hemera Technologies/ Images
Suggest a Correction