Archive for Sunday, July 25, 1999

GARDEN CALENDER

July 25, 1999

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Chemicals are the best means of controlling rampant nutsedge.

With all the wet weather this year, yellow nutsedge seems to be showing up everywhere.

This weed looks like a grass; in fact, it is often called nutgrass. Unlike grasses, however, nutsedge has triangular stems and the leaves are three-ranked instead of two-ranked -- the leaves come off the stems in three different directions. Yellow nutsedge is pale green to yellow in color and grows rapidly in the spring and early summer. Because of this rapid shoot growth, it sticks up above the rest of the lawn only a few days after mowing.

This weed is a good indicator of poor drainage, but it can be introduced into well-drained sites through contaminated topsoil or nursery stock.

Nutsedge is difficult, if not impossible, to control culturally because it produces numerous tubers that give rise to new plants. Some degree of suppression, such as gradually reducing the population or keeping it from spreading further, may be achieved by improving drainage in the infested area, mowing frequently, and, for cool-season grasses, fertilizing with nitrogen in early November. The latter practice helps because nutsedge vigor is reduced by frost more than most cool-season turfgrasses.

Contrary to what you sometimes hear, pulling the nutsedge by hand will not make the problem worse. You will have to be persistent. However, if you are going to treat with a herbicide, it makes sense to leave the nutsedge plants undisturbed so that the herbicide can be sent to the roots, rhizomes and tubers.

Several chemical products with varying efficacy are available. Manage has been available for a few years now and is very effective and safe to most turfgrasses. It is also the most expensive treatments, but if an infestation is not too severe, one application should take care of the problem. The Manage label says to apply it after nutsedge has reached the three- to eight-leaf stage. Waiting until this growth stage apparently results in improved transportation of the active ingredient to the underground tubers and rhizomes.

Basagran (bentazon) and MSMA (monosodium and methanearsonate) can also be used, but they are less effective than Manage, and often cause temporary discoloration of the desirable turfgrass. Basagran is somewhat more effective than MSMA, but both products often require repeat applications. MSMA is the least expensive of the three and is widely available in the homeowner market. MSMA has excellent control with repeat applications (10 to 14 days apart). MSMA is often sold under generic names like "nutgrass killer" or "crabgrass killer" because it is also used for postemergence crabgrass control. Check the label to determine whether such products contain MSMA.

-- The Garden Calendar is a service of K-State Extension and Research-Douglas County Office and written this week by Master Gardener Deanne Lenhart. For more information call the Master Gardener Hotline, 843-7058, from 1 p.m. to 4 p.m. Monday though Friday.

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