Nutsedge Identification (February 17, 2016)

Nutsedge is frequently referred to as “the world’s worst weed”. There are several species of nutsedge although only two species of this weed cause problems here and they are often confused. Although it is often called nutgrass, nutsedge is neither a nut nor a grass. It is instead a member of the sedge family. Unlike grasses, sedges have solid triangular stems. Grasses commonly have round, flat or oval stems that are hollow. Sedge leaves are thick, stiff with a distinct midrib and are arranged in sets of three at their base. Although there are many sedges, only two are weeds here and these are among the most damaging and difficult to control. These are purple nutsedge (Cyperus rotundus) and yellow nutsedge (Cyperus esculentus). Both are perennial weeds that are dormant during the winter. They produce seed although the seed is rarely viable and they spread vegetatively by below ground tubers (nutlets). These tubers are produced on rhizomes or below ground stems. Most of these tubers are within the top foot and a half although they can be found much deeper. Each tuber has up to seven buds from which new rhizomes and tubers grow. When shoots reach the surface they form basal bulbs and new leaves to keep this process fueled. In a single season one tuber can produce almost 2,000 new plants and 7,000 new tubers. These tubers can persist for several years and must be depleted to achieve complete control. Purple and yellow nutsedge respond differently to herbicides and it is important to make proper identification. Mixed populations can be found here and yellow nutsedge is, in general, easier to control. The following chart should help in properly identifying this weed.

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To contact Barry Tickes go to: btickes@ag.arizona.edu.