Keith Hansen

Even though fall is on its way, summer dry spells and pests can take a toll on our yards. By taking care of the lawn at this time of year, we can help it recover from summer stress, prepare it for winter and be stronger next spring.

WATERING: Even when it begins to cool off, the lawn will still need watering, just not as often as during the summer. Give lawns sufficient water to penetrate the soil 4 to 6 inches when you water in order to keep a healthy root system.

Perhaps the most important point regarding watering lawns in the fall is what time of day to water. Try to finish all watering by mid-morning. Watering late in the day results in grass staying wet all night allowing brown patch and take-all root rot diseases to get started.

FERTILIZING: If you had to pick the most important lawn care task to do in the fall, fertilizing would have to be right at the top of the list. Turf experts say that if you were only going to fertilize one time during the year, it should be made in the fall during September or early October.

Fall fertilization is the same thing as winterizing the lawn. Fertilizing now prepares the grass for the winter by building up food reserves. You can think of it as a bear storing up food in preparation for winter hibernation. Fall-fertilized grasses will come out of winter dormancy more vigorously next spring than those not fertilized. The objective is to keep the grass green and healthy right up to first freeze.

The type of fertilizer you should use is ideally based on a soil test. Without a soil test, use a 3-1-2 or similar ratio which is the same type recommended for spring and summer. Examples of 3-1-2 ratios would include 15-5-10, 18-6-12, 21-7-14. Important points to note are that phosphorus (the middle number) is low, and that nitrogen and potassium (the first and last numbers) are similar in proportion. Both nitrogen and potassium are important for imparting tolerance to stress.

Fall is also a good time to have the soil tested to see if it needs lime. East Texas soils tend to be acidic, sometimes strongly acidic, while the soils in the western 2/3 of the Texas are alkaline. Most turf grasses do best in slightly acidic soils.

Acidity is measured in units called pH, and an ideal range is between pH 5.8 and 7.2. When the pH falls below 5.8, the ability of grass to use fertilizer nutrients begins to dramatically decrease. In other words, the grass cannot use all the fertilizer you apply and the grass won't grow as well. Centipede is an exception and prefers an acidic soil.

Lime is used to raise soil pH back to an acceptable level. Some lawns do not need lime, and others need lime only every few years. The only way to tell whether your soil needs lime, and how much lime is needed, is to have the soil pH tested. Soil test kits for sending samples to the Texas A&M Soil Testing Lab or to Stephen F. Austin State University are available at all Texas Cooperative Extension county offices.

MOWING: Keep up with regular mowing. There is no need to raise or lower the cutting height in the fall. Leave it at the same height as during the summer. A higher cutting height in the winter does not promote winter hardiness, but could cause other problems. Check your grass after mowing. It should have smooth, not ragged or torn, cuts. Sharpen your mower blade at least a couple times a year. A sharp edge cuts the grass cleanly, resulting in quicker recovery.

PESTS: Chinch bugs can continue to be a problem in St. Augustine during hot, dry weather. Grub worms could be a problem in any lawn. They feed on roots, resulting in dying areas that are very loosely rooted. Check for the presence of grubs or chinch bugs before considering treating.

Fire ants will be more active this fall, and now is an ideal time to treat with a bait formulation to target both seen and unseen fire ant colonies.

DISEASES: Brown patch and take-all root rot are two fungal diseases that infect lawns, especially St. Augustine and Centipede grass, in the fall. These diseases are most active when the weather is mild (low 50s to mid 80s) and when leaves and crown area stay wet for several hours.

Brown patch damages the lawn in large patches that are often round, but not always. A diagnostic feature is that the leaves rot at the base and easily pull from the stolons (runners). Brown patch does not directly kill grass since the stolons remain alive and usually recover in spring. But it does weaken the lawn and results in delayed spring green up.

Take-all root rot also damages the lawn in irregular patches, killing infected grass. Symptoms are similar to grub damage in that the damaged grass is loosely rooted, but the difference is that roots are rotted with a dry decay, while grub-damaged grass roots have been eaten, do not appear rotten and grubs will be present. Symptoms of take-all root rot are usually seen in mid-spring after growth resumes.

Remember, diseases can only occur if the grass is kept wet for long periods of time, so water as infrequently as possible, and try not to water in the evening.

WEEDS: Lawns with serious early spring weed problems (Poa anna - annual bluegrass, chickweed, henbit, clover, lawn burweed, etc.) can benefit from a pre-emergence herbicide applied now to prevent these cool-season weed seeds from germinating.

Besides being unsightly, dense infestations of winter weeds can be damaging to lawns during spring green-up due to competition for sunlight, soil moisture and nutrients. And as winter weeds die, summer weeds like crabgrass can easily infest the holes left by the dead growth.

Pre-emergence applications should be made soon since winter weeds will be germinating with the cooler fall weather. Water immediately after application or the product will not work.

However, weak, drought-stressed, and newly seeded or sodded lawns could be hurt more than helped by a fall application of a pre-emergence herbicide, so you should skip the treatment for lawns under these conditions. Always read and follow label directions. Applying more than labeled rates can also damage turf.

Remember, a vigorous turf resulting from good cultural practices of proper mowing, watering and fertilizing is the best defense against weeds.


Keith Hansen is Smith County Horticulturist with Texas Cooperative Extension. His Web page is http://EastTexasGardening.tamu.edu Texas Cooperative Extension educational programs are open to all individuals without regard to race, color, sex, disability, religion, age or national origin.

Keith Hansen
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