For most homeowners, carpetgrass is a savior for poor soils or a nagging weed in an otherwise beautiful lawn. Since you’re reading this article, we’ll assume it’s the latter for you.
What is carpetgrass?
Carpetgrass (Axonopus) is a warm-season perennial grass species that is either planted as a low-maintenance turfgrass or is considered a weed in lawns planted with other grasses. Some homeowners in the South plant this grass (on purpose) because nothing else will grow in their lawns. It is a low-maintenance option for them and better than bare dirt or weeds in their lawns.
Carpetgrass is full of history and uses in the U.S.:
- Originated in Central America and the West Indies
- First used as pasture grass in the U.S.
- Often used as a nurse grass in centipede seed mixes
- Planted in the South (USDA zones 8 and hotter), from East Texas along the coast up through the coastal Carolina region
- Can thrive where few other grasses will. If your lawn is acidic, moist (but not flooded), and has poor fertility, carpetgrass may be a good option. It also will tolerate partial shade but prefers full sun.
One downside to carpetgrass is its need for weekly mowing during the summer months. Carpetgrass grows new seed heads every five days, which can be an annoyance for some homeowners. You can distinguish carpetgrass from other grasses by its tall, “Y-shaped” seed head. Some seed heads have only these two terminal spikes while others have a third spike beneath the “Y.”
How to get rid of carpetgrass
1. Get a positive ID on your weed
Identification is the first step. Grassy weeds can look very similar to each other, so it’s important to get a correct ID before you decide to treat them.
If you’re unsure which kind of weed you have, there are several ways to double-check. You can compare your weed with photos online; you can take the weed to your local Cooperative Extension office (or send a photo to their email); or you can upload a photo to your favorite plant identification app.
All of these tactics will help you to get a positive ID on your grassy weed.
2. Try the simplest solutions first
To defeat these weeds, you have to know something about them. Once you’ve determined that you have carpetgrass, use your powers of observation and observe the weeds in your lawn:
- Is the ground where the weeds live consistently moist? (Carpetgrass loves consistently moist soils.)
Homeowners with moist (not flooded) lawns love carpetgrass because it will grow in these conditions. If your lawn has high moisture in the area where these weeds congregate, aerate the lawn and see if the weeds die on their own.
Aeration machines have hollow tines that pull plugs of soil from the lawn. Think of it as a facial for your lawn. With more open pore space, air, water, and nutrients flow more easily to the roots. The result? A more beautiful, drier lawn — and less carpetgrass.
- Have you fertilized recently? What is your soil pH? (Carpetgrass loves acidic, low fertility soils.)
Another common-sense tactic is to get a soil test in the area where the weeds are growing. If your soil is low in nutrients, a good soil test will tell you how much to apply. Since carpetgrass hates fertile soil, this will likely reduce your weed issue. Ask your local Cooperative Extension office how to send in a soil test for your lawn.
- What time of year is it?
Carpetgrass prefers temps between 60 degrees Fahrenheit and 90 degrees Fahrenheit. It goes dormant once temps start to drop in the winter, and in spring, it’s late to green-up. If you don’t see it first thing in the spring, it’s probably just late to the party. You can put down a pre-emergent or spot-treat once they germinate.
- Have you recently seeded your lawn with a centipede/carpetgrass seed mix?
Did you seed a carpetgrass/centipedegrass mix? Carpetgrass is used in this case as a nurse grass — a grass that germinates more quickly than the dominant grass and will usually die once the dominant grass gets established. If your carpetgrass hasn’t quite died yet, wait until the drier days of summer. It will most likely die during that time. Also, give your lawn the proper fertilization to strengthen the centipede.
- Hand pull
Hand pulling grassy weeds can be difficult, but it can be done. If you don’t have too many, this may be an effective strategy to prevent the unsightly seed stalks from popping up in your lawn.
Since the seed heads grow every five days or so, stay on top of these by mowing them down. This won’t kill the weed, but it’s a good way to keep the yard from looking too bad until you can implement other control methods.
Remember, a full, dense lawn is the best way to control weeds. With a thicker, fuller lawn, the grass will do most of the work for you.
3. Spot treat
If you plan to aerate your lawn but it’s past the late spring or early summer (the ideal time to aerate warm-season grass), you might need to spot treat until you can take comprehensive action next year.
Natural spray options: Many options exist for natural post-emergent weed control. (Post-emergents treat weeds that you can see — weeds that have already sprouted up from the soil.) Horticultural vinegar (not the same as grocery store vinegar) is popular on grassy weeds like crabgrass, and there are many other store-bought weed killers you can buy as well.
Remember to look at the label and make sure it’s suited to kill grassy weeds, not just broadleaf weeds. (Broadleaf weeds are weeds with wide leaves, like dandelions; grassy weeds, well, look like grass.)
The most popular natural pre-emergent weed control is corn gluten meal. (Pre-emergent means before you can see it coming up from the ground.) Experts say its effectiveness may not be as reliable as conventional pre-emergents. In other words, you may not get the results you want after one application.
Chemical spray options:
There are numerous post-emergent weed killer options for grassy weeds like carpetgrass. Glyphosate (sold under several brands, including Roundup) rings a bell for most homeowners and is a widely available option.
When you select a product, make sure it’s safe for use on warm-season grass types. (Common warm-season grasses include bermudagrass, St. Augustinegrass, centipedegrass, and zoysiagrass.) Also, check that carpetgrass is included in the list of weeds.
Pre-emergent herbicides must be used before carpetgrass germinates in the spring. Timing is everything with pre-emergents and varies by state. The consensus is that when the soil temperature (not air temperature) stays between 50-55 degrees Fahrenheit for several days, it’s time to put down your pre-emergent. Your Cooperative Extension office can help if you’re unsure.
With pre- and post-emergent herbicides, you’ll have to choose between selective and non-selective products. Glyphosate, for example, is non-selective, meaning it will kill almost any living plant — including your grass, so be careful to spray only the plant tissue you want to kill. Selective herbicides are formulated to kill only specific plants.
If you live in the Deep South, you may have seen this grass and not known it. Contractors often plant this grass along roadsides. For residential use, homeowners with sandy soils also find this grass a functional option for a low-maintenance home lawn. It doesn’t like saltwater, though, so it isn’t a good option if your water is high in salt.
If you’ve never heard of carpetgrass, maybe you’ve heard it called by another name:
Mulching helps to keep carpetgrass out of your flower beds. Unlike some grass types, carpetgrass spreads by above-ground roots (stolons), so you don’t have to worry about this grass tunneling underneath the ground and into your flower beds. The above-ground roots and seeds are all you’ll have to deal with.
If the carpetgrass in your lawn needs more attention than you care to give, contact one of our local lawn care professionals. They have the experience and expertise to ID and control the most persistent weeds in your lawn.