Gardening Tip of the Week – Crabby About Crabgrass
Tips on Crabgrass Control
Crabgrass is an annual grassy weed that thrives in warm weather, and can appear anytime from spring through fall. Identifying Crabgrass can be difficult because it looks like many other grassy weeds, but there is a strategy for getting rid of it, as we explain below.
Once Crabgrass germinates, it rapidly dominates your lawn, notes Texas A&M Agrilife Extension. Crabgrass is a vigorous plant that grows faster than lawn grasses like St. Augustine and Bermuda. It also grows better under stressful conditions, such as drought, heat and low fertility, that cause your lawn to suffer.
It’s important to note that there are several factors that can exacerbate the spread of crabgrass. The University of Illinois Agricultural Extension’s LawnTalk includes soil compaction; light, frequent watering; and lack of fresh organic matter in the soil. Also, close-mowed lawns tend to open up space for weeds like crabgrass to invade. Crabgrass typically begins in these “weak” areas first and then spreads quickly to the rest of your lawn.
So your first job is to make sure you’re not making the problem worse.
#1 Improve Your Soil
A healthy lawn is one of the secrets to having fewer weeds. And the foundation for your lawn is the soil. Improve your soil as much as possible. Organic maintenance practices help ensure that your soil will contain all the necessary microbial life required to break down fertilizers and organic matter so that they can be fully and properly used by your lawn.
If you’ve ever watched the rain fall on a Texas yard, you’ve probably noticed that more water runs off onto the streets and sidewalks than what penetrates the ground. This is partly because the rain is often falling faster than it can soak in. However, it can also be due to soil compaction. Especially if you live in an area with heavy clay soil, it can be difficult for the water to penetrate through the clay.
Aerating your lawn will help reduce compaction and allow moisture and organic matter to penetrate more deeply. Top dressing with a high-quality organic compost twice a year is recommended to further help reduce compaction and improve your soil.
Likewise, applying Lava Sand or Texas Greensand will also help to open up your soil. (Read about our Top 5 Soil Amendments.) Unlike some soil amendments, these can be applied as a top dressing along with compost in a fertilizer spreader, making it pretty much a “no-brainer.”
Clay soil is also poor in nutrients. These additives each contribute additional beneficial ingredients to your soil.
Lava Sand is a red-to-black, porous volcanic rock used as the soil additive and conditioner. Because it is very porous, it increases the water-holding capacity of the soil. It also helps to create air pockets, which reduces compaction. Another “other-worldly“ benefit described by GardenIQ.com is that Lava Sand is paramagnetic. Paramagnetic rock as a sort of conduit for gathering the electro-magnetic energy of The Cosmos. This energy works on material such as plant waste (dead leaves, etc.), minerals, and compost to increase microbial development and the resulting plant growth.
Texas Greensand is crushed glauconite, a gray-green rock that is not only great for breaking up heavy soils but also provides a source of minerals — more than 30 of them — including calcium, iron, magnesium, and other nutrients. While these minerals are vital to plant growth, they are not generally found in fertilizers, so adding Texas Greensand replenishes the levels of these soil-builders.
#2 Apply a Pre-Emergent
Like other annual weeds, Crabgrass is spread by seed, which means you can make a big difference by putting down Corn Gluten Meal as a pre-emergent.
As always with Corn Gluten Meal, timing of application is critical. It should be applied just as seeds begin to germinate. For Crabgrass, this happens when soil temperatures are greater than 55 to 60F° for 7-10 consecutive days, and continues until soils reach 95F°. In North Texas, Crabgrass begins to germinate as early as mid-January. If left untreated, it will continue to proliferate through mid-July.
The good news is that because it’s an annual weed, it will die off every year during the first frost, says Lawncare.org. However, the seeds can survive the winter to germinate the following spring, so you’ll want to apply Corn Gluten Meal again in the fall to prevent spring germination.
#3 Use AgraLawn Post Emergent Crabgrass Killer
For post emergent control, we recommend AgraLawn Crabgrass Killer. Also recommended by The Dirt Doctor, AgraLawn uses cinnamon bark, which is fast-acting, but will not harm common lawns like St. Augustine and Bermuda.
When used properly, AgraLawn Crabgrass Killer causes very little reaction or yellowing to St. Augustine or Bahia lawns. Applying during the a.m. hours while morning dew is present works best, or you can wet the affected area with a hose, irrigation or spray bottle.
#4 Overseeding Your Lawn
Having a nice, thick, lush carpet-like lawn is not only every homeowner’s dream, it’s also a major success factor in the battle against weeds, including Crabgrass. One way to increase the density of your lawn is to overseed it.
Overseeding helps fill in sparse areas and thicken your grass, which helps create a barrier that keeps weed seeds out. Many North Texans also use overseeding as a way to keep their lawns green throughout the year. Warm-season grasses such as St. Augustine and Bermuda go dormant during the winter, which also opens up your lawn to weed invasion. Overseeding in the fall with Ryegrass — a cool season grass — helps maintain a green lawn through the winter.
Warning: Make sure you don’t overseed in the same area that you’ve applied Corn Gluten Meal unless you’ve waited at least 6 weeks after applying pre-emergent.
#5 Proper Irrigation
Crabgrass often invades areas that are watered too frequently. This is where proper irrigation plays an important role. Light, frequent watering favors Crabgrass and generally encourages shallow, weak roots. Texas turf grasses including Bermuda, St. Augustine, should be watered no more than once per week. Zoysia is even more drought tolerant and performs well with even less water.
Texas A&M Agrilife Extension emphasizes that your lawn only needs one inch of water every 7 days. Doing this, will encourage a deep root system and a healthier lawn. During the winter months, reduce your watering frequency to once every 15 to 20 days.
#6 Mow High
Mowing at the proper height will lessen the chances of Crabgrass taking hold in your lawn. Close-mowed lawns tend to open up, allowing weeds like Crabgrass to invade. Lawns mowed higher (over 2½ inches) tend to have less problems with annual grasses such as crabgrass.
Next season, focus your weed fighting efforts on improving your soil through organic practices, along with proper mowing and irrigation. A healthy yard will make your job easier and help keep weeds out of your lawn and flowerbeds.