Saturday, July 2, 2016 By: Ask A Master Gardener

Controlling Nutsedge Weeds in Lawns

Nutsedge is tough weed to control

Bill Sevier: Ask a Master Gardener | Posted:

Saturday, July 2, 2016 12:00 am

Q: There is what looks to be nutgrass growing in my lawn. It is spreading; what can I do? A.K., Tulsa
A: Nutgrass is a common name for the troublesome nutsedge weeds. These weeds are sedges, not grasses nor are they broadleaved weeds. Therefore, the usual “weed killers” on the garden center shelves will not be effective herbicides.
Many sedges are troublesome in agriculture and for homeowners. Weed experts list yellow and purple nutsedge in the top 10 of the most difficult weeds to control. We have mostly yellow nutsedge; purple grows farther south. Another sedge called green kyllinga has also become a problem in lawns in recent years.
Yellow nutsedge is a vigorous grower. It grows twice as fast as turfgrass and can be seen towering above turfgrass a couple of days after mowing. The sedge is found in clusters. On inspection, the stems look like grasses but are different in that the stems are solid, triangular and have edges. This is behind the adage “sedges have edges.”
Nutsedge reproduces in two ways — from seeds and by underground “nutlets.” Nutlets are produced in abundance by roots called rhizomes. They are the source of the common name “nutgrass.” The nutlets may survive for years in soil, and each can give rise to a new plant when growing conditions are favorable. Spread of nutgrass to your lawn is often related to imported topsoil, mulch or contaminated nursery plants.
Control of nutsedge includes cultural and herbicidal approaches. Pulling the sedge will not remove the rhizomes or nutlets but can be effective if the plant is removed while young and before nutlets form. Because nutsedge thrives in moist soil, reducing the moisture in the area will help but will not eliminate established plants.
Several effective herbicides are available for yellow nutsedge. Some of the brand and chemical names are Basagran (bentazon), Image (imazaquin), SedgeHammer (halosulfuron) and Ortho Nutsedge Killer (sulfentrazone). These chemicals are safe to use on all of our turfgrasses, with the exception of Image. It cannot be used on fescue lawns.
Of these herbicides, SedgeHammer is a little more effective and also the most expensive. However, all of them are beneficial and are recommended.
These herbicides should be used in summer when nutsedge is actively growing, and most will need to be used twice during the summer, according to the labeled directions. Nutgrass has a waxy coat, so some of these chemicals will need a commonly available additive called “spreader sticker,” a soap-like solution that helps it stick to the plant.
These chemicals cannot be used among flowers or in the vegetable garden. For these areas, it’s either hand-pulling, digging or, if the weed is isolated in spots, the careful use of glyphosate, found in Roundup and other brands. Glyphosate does not migrate in soil, and most of the preparations are labeled for use around vegetables.

For more information or to ask a question about gardening, contact the Master Gardeners at 918-746-3701 from 9 a.m.-4 p.m.

Garden tips
§  Harvest onions when most of the plant tops have fallen over. They will keep longer if the tops are allowed to dry completely before storage. Store in shaded area so that the onions will be well-ventilated.
§  Most varieties of mums are more productive if “pinched back” now. Either pinch off with fingers or cut to remove an inch or so of limb tips above a leaf. This results in the growth of new limbs and a fuller plant. Do not pinch after mid-July or it will interfere with fall blooming.
§  Watch for tiny, sap-sucking insects called aphids on roses, perennial flowers, shrubs and vegetables (especially tomatoes). They produce a sticky substance called “honeydew”. Many can be dislodged with a hard spray from your garden hose, or two applications of insecticidal soap will usually greatly reduce any aphid damage to your plants.
§  Crapemyrtles are one of the few shrubs that should be planted in the middle of summer. Growth of new roots of these plants occurs best with summer soil temperatures.


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