9/28/2022 - By Scott Renfro

Yellow nutsedge is a perennial weed found in most agricultural, horticulture, and nursery crops and has adapted to survive in a diverse range of soil types found throughout North America. This weed spreads like wildfire, and it can truly be a challenge to remove from your growing beds once it germinates.

Yellow Nutsedge: One of the Worst Agricultural Weeds

I consider it one of the worst agricultural weeds to eradicate due to its multiple reproductive structures. Yellow nutsedge reproduces from two underground structures called rhizomes and nut-like tubers. The reproduction process begins with the development of long scaley white rhizomes that can extend 6 feet wide and 8 to 12 inches below ground with hard, round tubers at the tip.

Over the course of one season, a single yellow nutsedge weed can produce hundreds of thousands of tubers, which shed their scales and form bulbs that give rise to vegetative roots and shoots. Most of the reproduction begins around 3 weeks after shoot emergence from an existing tuber or when daylengths reach 14 hours. Later in the growing season around late summer, it will produce overwintering tubers that germinate the following year, occurring around May in Oregon.

Yellow Nutsedge Appearance and Characteristics

These overwintering tubers contain a water-soluble chemical in their skin that inhibits dormancy. When irrigation or rainfall occurs, the chemical is washed off thereby inducing germination only after soil temperatures rise above 54°F. The weeds occur in groups of three at the base giving it the characteristic triangular cross-section when cut, with flat and shiny leaves that have a yellowish-green color.

Mature plants form clumps and produce flowering stems that can reach 3 feet tall. Flowering occurs when daylength is around 12-14 hours, and viable seed is produced, about two to three weeks after flowering. However, germination is very low due to the poor genetic diversity among its population.

Management of yellow nutsedge is challenging due to its vast network of underground reproductive structures. However, pre-emergent herbicides like S-metolachlor can provide adequate suppression if applied in late fall and late winter. There are also a few post-emergent herbicides that have been proven effective if applied before the 5^th leaf stage of development. These include products like Halosulfuron-methyl and Sulfentrazone.

Nonchemical suppression of yellow nutsedge is achieved through cultivation since most of the tubers are in the top 6 inches of the soil and they are very sensitive to drying out. Tillage in late spring and early summer after the tubers have germinated and before they produce new tubers will greatly reduce subsequent populations.

For more information on yellow nutsedge reach out to your local Harrell's rep, and check out this article for additional information on nutsedge control.