The end of summer doesn’t mean an end to yard work. Warm-season grasses still need fall maintenance before they go dormant if they’re going to have a healthy re-emergence in the spring.
Here are some lawn care actions you can take this fall to prepare your turfgrass for dormancy and survival over the winter months.
- Keep Watering
Your lawn needs less water with cooler fall temperatures. Continue to water but turn on the irrigation controller’s “seasonal adjust” feature to reduce the summer schedule zone watering times.
When your lawn goes dormant (soil temperatures consistently below 55°F), irrigate once or twice a month. Moisture in the soil keeps the grass roots warmer, and water in the root cells acts as an insulator from freezing temperatures.
- Rake Leaves Regularly
Don’t let leaves sit on your lawn. Rake them all up every 3 or 4 days or catch them with a grass bag when mowing. A thick layer of leaves will block water and sunlight and smother the grass. It also makes your lawn more susceptible to disease and pests.
An alternative to raking or using a mower bag is cutting the grass with a mulching mower. It shreds the leaves on the lawn into pieces about the size of a dime, which easily decompose and add nutrients to the soil. Mulching blades and kits are also available as mower add-ons. A regular mower will shred leaves as well, although it will take several passes to make the pieces small enough.
- Continue to Mow
Continue mowing warm-season grasses to their proper height until they go dormant. Remember to never cut off more than 1/3 of the leaf blade height. If winter annual or perennial weeds appear, you’ll need to mow regularly to keep them under control.
There are low and high optimum mowing heights for each warm-season grass type and cultivar (variety of a specific plant created and maintained through cultivation) recommended by Texas A&M AgriLife Extension Service:
St. Augustine — 2.5 to 4 inches
Bermuda (common) — 1.5 to 3 inches
Bermuda (hybrid) — 1 to 2.5 inches
Buffalo — 2.5 inches to 4 inches
Zoysia (coarse) — 1 to 2.5 inches
Zoysia (fine) — 1 to 2 inches
- Fall Fertilizer for Warm-Season Grasses
The best time to apply fertilizer in the fall for warm-season grasses is 6 to 8 weeks before the first expected frost (4 to 5 weeks for Bermuda grass). Be sure to water it in so it moves down to the roots. Select a quick-release fertilizer low in nitrogen (N), and if possible, split it into two smaller applications rather than a single one.
Potassium (K) can also be applied in the fall. It has many benefits, including disease suppression, and stress relief from cold temperatures.
A soil test will tell you if the potassium amounts are low. You should get your soil tested every year, either in the spring or fall, so you know what fertilizer to buy with the correct nutrient percentages for your soil.
- Apply Pre-Emergent Herbicides to Prevent Weeds
Apply pre-emergent herbicides to control annual winter weeds before they emerge on established lawns. This should be done when the soil temperature reaches around 70°F for 2-3 consecutive days. A soil temperature map, soil temperature probe, or meat probe can help you determine the application days. If you see any weeds above ground, spot treat them with post-emergent herbicides.
Before choosing a herbicide you’ll need to identify the type of weeds in your lawn. Herbicide labels usually list the applicable weed species, application rate, timing, activation method such as irrigation, and appropriate turfgrass.
Apply herbicides before fertilizing or mowing. Wait at least a week before using a fertilizer, and 2-3 days before mowing, to give the grass time to recover from any stress caused by the herbicide.
- Manage Fungal Diseases
As temperatures drop, many warm-season lawn diseases such as large patch and take-all patch become more active. In lawns where a known disease recurs, you can apply a preventative fungicide at the same time as you apply your pre-emergent herbicides.
However, if the disease is unknown, the key to choosing the correct fungicide is a proper diagnosis of the disease. If you need assistance, ask a lawn care professional, or contact your Texas A&M AgriLife Extension County Office to speak to a master gardener.
Garden centers and nurseries carry fungicides, but the most effective ones are available only to lawn care professionals. If you’re treating the fungal disease yourself, you can also apply the fungicide at the same time as fertilizers if both are activated by water.
- Monitor for Insect Pests
Watch out for certain insect pests that are active in the fall, especially in Bermuda and St. Augustine turfgrass:
Watch your yard for armyworms, especially after early fall rains and up to the first frost. The larvae caterpillars are green, brown, or black, with white to yellowish lines running from head to tail. There’s a distinct white inverted Y between the eyes. They’re very small at first (1/8 inch), but after feeding for a few weeks can grow up to 2 inches long.
The caterpillars chew the green layer at the tips of the grass blades, creating a transparent appearance. If left untreated, the caterpillars will continue stripping green tissue from turfgrass, until damaged areas turn brown.
Fall armyworms can destroy a lawn within a few days, so treat quickly when you see visible leaf damage, or more than 3 caterpillars per square foot. Treatment options include:
- Insecticides containing bifenthrin, carbaryl and permethrin
- Low-impact insecticides such as halofenozide (small caterpillers only) and spinosad
- Bacillus thuringiensis (Bt) products that won’t harm beneficial insects. Bt residue doesn’t last on turf for more than 1-2 days
White grubs feed on grass roots until the end of October when the temperature drops. They then move deeper below ground and go dormant until spring.
Monitor your lawn for irregularly-shaped dead or dying patches. The damaged turfgrass should pull up easily from the ground, where you’ll see white grubs in the top few inches of soil.
White grub treatments:
- In September and late October apply short-lived insecticides such as carbaryl and trichlorfon to kill all grub life stages
- Use nematodes as an organic option (within the genera Steinernema and Heterorhabditis)
- The following June (south Texas), or July (central and north Texas), apply a preventive insecticide, such as imidacloprid and halofenozide
Overseed your Bermuda lawn with a temporary annual or perennial cool-season ryegrass if you want a green lawn throughout the winter. Overseeding is not generally recommended for other warm-season grasses.
Fall overseeding is done from mid-October to early November when Bermuda grass has gone dormant, and the ryegrass won’t be competing with it for sunlight and nutrients. Don’t overseed if you’ve applied a pre-emergent herbicide — it will prevent the rye seed from sprouting. Wait another year before overseeding.
Perennial ryegrass is often preferred for overseeding because it provides a darker color, is more disease resistant, and requires less mowing. By comparison, annual ryegrass is less expensive, germinates faster, and dies out more quickly in the spring.
Here are some guidelines for overseeding success:
- Mow your permanent grass to its recommended height before sowing the rye seed
- Sow half the seed going east-west, and the other half going north-south
- Water lightly every day or two until the seed germinates. Once established the ryegrass will require regular irrigation
- Mow the established ryegrass to the lowest recommended height for your permanent grass
- In mid-winter, fertilize the ryegrass with a high-nitrogen fertilizer
Call the licensed irrigators at Smart Earth Sprinklers at 512-694-1147 or contact us online for your sprinkler system inspection, repair, and maintenance needs.