Nutsedge

By Barry Tickes, UA Area Agriculture Agent

Nutsedge has long been one of our most difficult to control weeds. It is often misunderstood and progress in controlling it has been slow. Nutsedge is often referred to as nutgrass although it is neither a grass nor a nut and is very different from both.

Nutsedge is a monocot, like grasses, but is in the sedge or cyperaceae family. The ‘nut’ refers to the below ground tubers which are not nuts but have nutritional value and are sometimes eaten in famine stricken areas of Africa.

There are more than 5,000 separate species of sedges that exist worldwide. Some of the most widely known sedges are water chestnut and papyrus sedge which was used to make the ancient writing material.

Sedges are easily distinguished from grasses by the solid triangular flower stems. Sedges are almost all perennials while grasses, which have round stems, are most frequently annuals.

The two sedges that are a problem in the Yuma area are purple nutsedge, cyperus rotundus, and yellow nutsedge, cyperus esculentus. Purple probably accounts for 75 to 80 percent. These are not hard to identify but people sometimes have trouble distinguishing them.

Both are perennials and grow actively at the same time. Both grow from tubers and rhizomes. The seed is rarely viable and both are spread vegetatively from the tubers and rhizomes. They spread so rapidly and are so prolific that people are often surprised that less than five percent of the seed produced is viable.

The leaves do not have ligules or auricles and have a ridge along the midvein.

Yellow and purple nutsedge are similar at early growth stages but are not hard to distinguish later on. The leaves of purple are blunt and less pointed than yellow. As expected, the seed heads of purple are purple and yellow are yellow.

The tubers of purple are much larger than yellow; irregular shaped, connected by chains, bitter in taste, and have a distinctive almond odor. Yellow nutlets are small, round, not connected, and have a more sweet taste.

Nutsedge is a weed that gets worse each year because of the absence of highly effective herbicides and cultivation spreads it. Remember that the seed is not viable. The only way this weed spreads significant distances is mechanically. Soil movement should be minimized as much as possible where nutsedge is a problem.

Almost all herbicides with activity on this weed are only partially effective and require multiple applications over multiple years. It is necessary to control the below ground nutlets and rhizomes. They can persist for many years and continually put out new growth.

Nutsedge is so prolific that if a herbicide is not highly effective, the infestation is back to where you started one year later.

Several herbicides have nutsedge on the label and range in control from 20 percent to 90 percent. Twenty of these herbicides are contained in this table, "Herbicides with Activity on Nutsedge".

Question of the Week – Weed Science - What is the difference between goosefoot and lambsquarter?

A - No difference, herbicide tolerance

B - Color, appearance.

C - One is roasted and the other is baked.

D - Check Barry's answer (video).

Contact Tickes: (928) 580-9902 or btickes@ag.arizona.edu