William H. McCaleb
Program Assistant, ANR
Virginia Cooperative Extension
I know we all enjoy the beauty of those first blooming shrubs as they will really give you the Spring Fever. Thinking ahead to the greening of your turf, many of us have an annual grass called crabgrass. If you have been fighting crabgrass in your lawn, year after year, and want to know the best management practice to control this pesky weed, read on! There are pre-emergent products and post emergent products on the market that can be used on your lawn, or you can be pro-active and use some cultural means of controlling crabgrass.
This smooth crabgrass should treated in the spring. Wide blade crabgrass can also be found here in Southside. Treatment is the same for both types.
If you want to cut down on the emerging crabgrass, if you will cut your fescue or other cool season grasses at a 3 1/2 to 4” height, you will help mother nature shade the dormant seed so it doesn’t germinate. And a quick jump into the future, remember grasses must reseed, perennial and annual grasses like crabgrass. If you cut the tillering heads off your crabgrass in the fall, you will cut down on the amount of viable mature seed that will lay there the next winter and spring forth in the following spring.
Or, getting back to using pre-emergent products as the Forsythia blooms drop, remember that if you use some of the more popular products that have both fertilizer and the pre-emergent herbicides, you will be cutting your turf more often when you add the nutrients in the fertilizer to your lawn in the spring. Virginia Cooperative Extension always recommends, for a healthy root system and grass plant, fall fertilization is recommended, not spring fertilization. Spring fertilization creates faster more tender growth that also is the right way to increase some of our fungal issues in turf, such as brown patch, dollar spot, fairy ring, just to name a few. If you use a pre-emergent, you may want to consider a product that does not have fertilizer in it. With the current rising costs of lawn, garden, and agricultural products, you may want to give it serious consideration. Just to recap what I said is prevention is a good line of defense and promoting a unhealthy environment for crabgrass is a good thing. Pre-emergent chemicals prevent seed from germinating. Crabgrass seed lies in the soil in wait, biding its time, for just the right temperature and moisture to emerge and wreak havoc in lawns for another season.
I should mention that many of our seed eating birds do like crabgrass seed, if you were wondering how new patches get started. The birds eat, but with an inefficient digestive system, seed comes out fertilized and ready to grow.
A little history on crabgrass, as mentioned earlier, it is an annual grass. No matter how much effort you’ve taken in previous years to control crabgrass, our soils remain a veritable seed bank of crabgrass seed from years past. This warm-season summer annual grass germinates from seed just prior to the first significant growth period of our lawn grasses. And as annual plants are genetically programmed to do since they live such a short time, they grow like mad and produce plenty of new seed under optimal temperature conditions. Hence, a warm-season crabgrass plant has an inherent competitive advantage against cool-season lawn grasses (fescues, bluegrasses, and ryegrasses) and can even slug it out with perennial warm-season grasses (bermudagrass (wiregrass) and zoysiagrass) because it gets a jump on them in early spring growth.
Post-treatment considerations? Costs of post-emergent control, again, are much higher than pre-emergent products and have been found to be not as effective. One thing required for all post-emergent herbicide applications is to water the product into the soil with either a suitable rainfall or irrigation event. The only way the product works is if it gets into the top of the soil profile to form a chemical barrier that germinating seedlings penetrate. Appropriate moisture is critical to optimize herbicide efficacy. And remember to keep all products on the turf and off hardscapes and roadways to avoid any runoff. This is the easiest way to protect our valuable clean water resources.
If you have questions about crabgrass control, please contact your local Halifax Virginia Cooperative Extension office on 434-830-3383 (the Master Gardener Help Desk) and if a Master Gardener is not in the office, they will get back to you as soon as possible. They may call from a different phone number as we have our volunteers checking the Help Desk daily during the week. You can also stop in the office Monday-Friday from 8 a.m. – 5 p.m. Monday through Friday.