While some of us in Tulare County have ditched our lawns for a xeriscape or drought-tolerant landscape, many of us still retain a turfgrass lawn. There are undeniable benefits to a turfgrass lawn: healthy lawns contribute to improved air quality by acting as traps for dust and other airborne particles, they reduce carbon dioxide in the atmosphere while giving back oxygen, and they also provide a soft even surface for outdoor activities. However, for many lawn-lovers, nothing makes them crabbier than the sight of ungainly weeds spoiling their green and pristine source of joy.
One of the most common summer weeds in the Central Valley is crabgrass. While you might think it got its name because of the mood it puts us in when it invades our lawn, other sources state that its rosette growth pattern resembles a crab—or that it grew in salty marshes and was eaten by crabs. Regardless, crabgrass is not native to North America and apparently has some use as a forage crop, as it was introduced into the U.S. in 1849 by the U.S. Patent Office as a potential forage crop.
Crabgrass is an opportunistic annual grass that sprouts in the late spring, and its ungainly, coarse-textured clumps can invade and crowd out desirable turfgrasses. Unmowed, it can grow to a height of 6 inches. It spreads by seeds and also by putting out runners which sprout roots when they touch the ground. It is a summer annual, well-situated to our hot, dry summers. It will die out in the cold winter weather, leaving behind an unsightly bare patch. But the problems don’t end with the growing season, as one plant can leave behind a many as 100,000 seeds, ready to germinate the following spring—and in years to follow.
UCANR (University of California Agricultural and Natural Resources) states that crabgrass is easy to control in both turfgrass and ornamental beds by applying preemergent herbicides before it germinates, or postemergent herbicides after it germinates. If you choose the chemical route, read the label to make sure the product is safe to use on your turf type and around the ornamentals in your landscape.
While crabgrass is fairly easy to prevent with preemergent herbicides, it can be difficult to control with postemergent herbicides. For preemergent herbicides to be their most effective, it is best to apply them about three weeks before crabgrass germinates. Control is important before seeds set because once the seeds are spread, they can remain in the soil and able to sprout for at least 3 more years. According to John Karlik, Horticultural Advisor in Kern County, crabgrass seed begins to germinate around the first week of February in our area. A handy way to remember when to apply a preemergent herbicide is to associate its application with the Super Bowl.
Cultural controls should always be considered before a chemical approach is used. (Cultural controls are practices which modify the environment to limit a pest.) A thick lush lawn can prevent crabgrass from becoming a problem. Lawn care practices to avoid because they favor the development and spread of crabgrass are: frequent, shallow turf irrigations; mowing lawns too short; fertilizing lawns at the wrong time of year; and lawn mowers spreading crab grass and other weed seeds from site to site.
So try to do the opposite of the above practices when you take care of your lawn. Increase the vigor of your turfgrass by: using the proper mowing height for your particular turf (higher grass length will help decrease seed germination), selecting the best turf species for our area (warm season grasses such as Bermuda are better for Tulare and Kings Counties), applying fertilizer at the correct time of year (Bermuda grass in summer, not early spring), irrigating properly, and cleaning your mower after using it in a weedy site.
Other cultural methods to control crabgrass are:
Mulching: Mulch acts as a suffocating blanket by preventing light from reaching weed seeds. At the same time, mulch holds moisture for your plants and provides nutrients for your soil as it decomposes.
Hoeing and hand pulling: This is best done when the plants are young and smaller. Crabgrass has shallow roots; using weeders, a trowel, or hoe will make the job easier.
Solarization: Soil solarization with clear plastic is effective for eradicating crabgrass plants and seed if you apply it during periods of high solar radiation. However, this is not practical in a lawn setting, unless you wish to kill your lawn, too. For more information: visit tinyurl.com/nts9594p.
If you pull up crabgrass from your lawn, prevent it from coming back by filling in the bare patch with grass seed. Cover the seeds with a light layer of topsoil, and water well to help the seeds sprout. Wait to mow the new grass until it reaches 3 inches tall. Don’t toss the uprooted weeds in your compost pile because they could still reseed. Instead, it’s better to toss those weeds in the trash.
There are several chemical herbicides available for crabgrass control after it is actively growing, but these often aren’t necessary. Remember that your goal should be to become a better lawn gardener and not rely on herbicides.
For more information on weeds (including crabgrass) in turfgrass, visit tinyurl.com/56za4kz5.
This column is not a news article but the advice of the writer and does not reflect the views of Mid Valley Times newspaper.