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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