Will Roundup Painted on the Foliage of Yellow Nutsedge Kill It?

Growth Habits

• Yellow nutsedge is designed to survive, thrive and spread, and it infuriates homeowners. Seedlings resemble grass, making them difficult to detect. Rhizomes spread 2 to 8 inches from parent plants in a radiating pattern. Leaves and stems sprout at the ends of the rhizomes (tubers can also form at the end of rhizomes) while also sending down a fibrous root system. When the seedling has about five to six leaves, the root system begins producing tubers -- this repeats every two to three weeks during the summer.

Tubers

• Controlling tubers is key to managing yellow nutsedge. To limit tuber production, small seedlings need to be removed by hand or killed with an herbicide before tubers form. Timing is critical. Roots and tubers reside primarily in the top 6 inches of soil, although they can reach depths of 8 to 14 inches. One tuber can produce three plants, and one plant ultimately produces hundreds of tubers that remain dormant through the winter.

Mechanical Control

• Pulling mature plants out of the soil leaves viable tubers behind; lifting the plant out by digging deeper than 6 inches might remove the tubers with the plant. Tilling a lawn with yellow nutsedge only makes the problem worse by spreading tubers. Determined gardeners spend many hours carefully lifting plants from their soil only to repeat the process the next season.

Chemical Control

• Use of Roundup on young, actively growing seedlings kills the plant before tubers form, although it doesn’t move through the root system. Painting or carefully spraying Roundup on the plant kills the leaves; however, the tubers remain unaffected. Diligent treatment of foliage eventually depletes the energy that’s stored in the tubers. When a single tuber sprouts, it develops and sends out multiple rhizomes; watchful homeowners will need to quickly address future seedlings with repeat treatments.

Roundup in Lawn

• Apply Roundup to young yellow nutsedge seedlings when they haven’t been recently mowed. Remember that this nonselective herbicide will kill grass as readily as weeds. Use this with caution, and realize that repeated applications will be required on yellow nutsedge – Roundup has a limited suppression capability.

Chemical-Free Approach

• Chemical-free lawn supporters recommend mowing lawns with yellow nutsedge high in the summer with the assumption that dense, healthy lawns out-compete most weeds, including warm-season weeds. Regarding yellow nutsedge, they also recommend watering infrequently and deeply to discourage the growth of this tenacious weed. Experience has proven that this approach fails.