7 August 2018
Kill crab grass and be one step closer to having a perfect lawn.
Crabgrass is a tough opponent, but with a lawn spreader, a pump sprayer and a few turf products you can get rid of crabgrass in the spring and control it throughout the summer.
OK, your lawn has been growing for a couple of months and you notice light green blades thickening up your Kentucky Blue. Before you think your lawn is having an exceptional season, think again: It’s likely to be young crabgrass.
Pulling, at this early stage, is a surprisingly effective way to get rid of crabgrass. But if the weed has pushed up three or four rows of leaves, inspect it carefully before you snatch it. If you spot a slender, green seed head that is still closed and folded up against the leaves of the plant, go ahead and pull it, too.
However, after the seed head tines have spread out like a fork, leave it alone. Otherwise you’ll scatter scads of seeds right over that nice big hole you’ve just created by removing the mature weed. You might as well be trying to cultivate new crabgrass!
Come fall, seed bare and patchy areas. With good lawn care practices, you’ll soon crowd out those fallen crabgrass seeds.
Lightly mist masses of immature crabgrass with a postemergence herbicide. Usually it’s too embedded to pull without yanking lots of your desirable grass with it.
Spray postemergence herbicide directly on crabgrass after it has sprouted. Pulling is equally effective, but if the roots are deeply embedded in your lawn, it may be tough to pull them out without pulling grass chunks too. It’s not worth spraying a postemergence product on crabgrass that has gone to seed. It takes about two weeks for the herbicide to work, which is about how long it takes the plant to finish its seeding process. If it has gone to seed, you’re better off waiting for next spring and applying a preemergence product then.
Post-emergence herbicides are most effective when the soil is moist and the plants are dry. Read the label for specific instructions. Typically you apply it with a hand pump sprayer. It’s best to apply it on a hot day when there’s low wind. If temperatures are too low, the product may be ineffective. Unless the crabgrass is young, you’ll probably have to reapply the product a few days later (according to the label) to kill the plant.
After postemergence application(s), keep an eye on the treated area. In extremely dry conditions, water two days after the application to aid absorption. If your grass near the treated area is turning brown, you probably were a little heavy handed.
Soak the damaged area with water to dilute the chemical and avoid further damage. Also be on the lookout for new crabgrass sprouts. These will require another herbicide treatment, or if there aren’t too many, simply pull them. Be sure to seed these areas in the fall.
Don’t waste your money on a postemergence herbicide in the fall as a route on how to kill crabgrass, when the temperatures are falling. The herbicide won’t be effective and the plant will soon die anyway.
The best way to stop crabgrass is to shade it out with a thick, healthy lawn. A thick lawn provides a dark canopy of grass blades over the seeds, so they won’t sprout. Follow these good grass-care practices.
Watering: A thorough watering once a week will encourage the grass’s root system to go deeper, making the whole lawn more hardy and heat tolerant. Avoid short, frequent waterings. These “sips” will promote a shallow, weaker root system in your lawn.
Mow: As a rule, grass should be mowed to a height of 2 to 3 in. Mowing it shorter than 2 in. will reduce the grass’s vitality and give weeds a chance to move in. Be sure to keep your lawn mower blades sharp so they won’t tear the grass. Leave grass clippings on the lawn as a natural fertilizer.
Reduce compaction: Weeds thrive in areas where compacted soil deprives the grass roots of the air and water circulation they need. If your yard is prone to compaction, rent and run an aerator over it every other year, especially if your soil contains a lot of clay.
Fertilize right: Avoid lawn fertilizer that say “quick green-up” on the label. These have excessive nitrogen ingredients that will actually weaken your lawn over time, making it more susceptible to weeds. Instead, select a fertilizer product with half of its nitrogen in a slow-release form. For a 1,000-sq.-ft. lawn, use less than 3 lbs. of nitrogen annually.
Reseed: Weed-damaged or thin areas should be seeded (sometimes called “overseeded”) in the fall, when the days are warm, the nights are cool and you have dew in the mornings.
Some spots need special attention
Lawn near driveways, sidewalks and curbs or on south-facing banks absorbs a lot of heat during the summer months, which makes it more susceptible to crabgrass. Limit crabgrass growth in these areas by doing a targeted double treatment. After you’ve treated your entire lawn, go back and make another pass, as one option on how to kill crabgrass, about 6 to 8 ft. wide, along these areas (and make sure to sweep it off hard surfaces afterward). This will help keep crabgrass from taking hold along these heat absorbers.
Kill it all and start over!
Expose bare soil
Kill off patches of lawn with nonselective herbicide in the fall if more than half the area is weeds. When it’s safe to replant (check the herbicide label), soak the patch with water and rake off dead grass and thatch to bare the soil.
While we all admire those who relentlessly defend their turf against crabgrass, there comes a time when the best strategy is to give up. That time is when your lawn only has 30 to 40 percent desirable grass left in a given area and the rest is lost to crabgrass and other weeds, and all options on how to kill crabgrass have been exhausted.
Begin by killing all the vegetation. On a low-wind day, apply a nonselective herbicide that is approved for lawn use, like Round-Up or Kleen-Up. Follow the label directions exactly. Depending on the product, weeds and grass will die and dry up in five to 14 days following application. Then renovation can proceed.
Thoroughly soak the area to give your new grass its best chance for a good start. Check your watering depth by pushing a spade into the ground and pulling it back to get a deep view of the soil. If the soil is moist to a depth of 6 to 8 in., you’re ready. For patchy bare areas and turf-free areas up to about 8 ft. square, use the spade technique for seeding. It’s effective, although it would be slow and tedious on areas that are much larger. Scuff up the dead vegetation with a rake and, using a spade, make 1/4-in.-deep furrows about 2 in. apart. Broadcast your grass seed, then flip a rake upside down and knock the seeds into the furrows. These furrows ensure that the seeds will make good contact with soil; they provide some moisture-retaining shelter as well. Then be sure to keep the seeds and soil moist. Continue to baby your new grass until after its first mowing. Do not apply crabgrass preventer to freshly planted areas.
Pre-emergent herbicides are the most effective and economical way to control crabgrass. But if you’d rather not use herbicides, you can try hand-weeding individual crabgrass plants in late spring before they get too big. They pull easily in soft ground after a rain.
Learn more on how to eliminate weeds in your yard, contact Monnick Supply in Marlborough and Framingham, MA.
135 Maple Street,
Call (508) 318-4788
Mon-Sat 7:00am to 5:00pm
759 Waverly Street,
Call (508) 386-9876
Mon-Sat 7:00am to 5:00pm