Many weeds cause problems in the lawn this time of year. Weeds such as annual bluegrass, henbit and chickweed have popped up and need to be controlled before spring. These weeds live one growing season, produce seeds and die. The seeds germinate when conditions are favorable, and the process begins again.
Perennial weeds also cause trouble this time of year. These come back each year from roots or seed. The No. 1 perennial weed is the dandelion.
One of the more difficult weeds to control is annual bluegrass, Poa annua. This is a grassy, yellow-green weed that in the spring has a silvery seed head. This weed seems to appear overnight, but it has been present since late September or early October. Some of the seeds will germinate in March with favorable conditions. Annual bluegrass likes areas that have wet, compacted soils. It also likes areas where high amounts of nitrogen fertilizer have been applied. This weed seems to appear in Bermuda and Zoysia lawns more than Centipede or St. Augustine.
Annual bluegrass can be reduced by proper lawn management. Aerating the soil reduces compaction and allows excess moisture to move more easily through the soil. Another way to reduce excess moisture is to water the grass only when needed. This means watering deeply once a week instead of applying smaller amounts of water more often.
Don’t apply more nitrogen than the grass needs. Bermuda grass needs 4 pounds of nitrogen per 1,000 square feet per year, and Zoysia needs 2 to 3 pounds of nitrogen per 1,000 square feet per year.
To control annual bluegrass now, either pull it or use a herbicide such as atrazine. It will provide post-emergent control for this weed. Atrazine also provides pre-emergent control for 30 to 45 days after application. Atrazine is labeled for use on Centipede, St. Augustine and Zoysia. If you use atrazine on Bermuda, apply it in the next two weeks.
Other troublesome weeds are henbit, chickweed and dandelion. Henbit has a purple flower in late winter and early spring. The stem of the plant is square or four-sided. It is in the mint family and has a slight odor when crushed. Henbit likes areas of the lawn where the grass is thin or open, or areas that have been disturbed. Chickweed is a mat-forming weed that has small oval-shaped leaves arranged opposite of each other on the stem. Chickweed flowers are small, white clusters on the end of the stem. Most of the chickweeds are annuals, but mouse-ear chickweed is a perennial that gets its name from hairy, grey-green leaves. Chickweed, like henbit, prefers areas where the turf is thin and the soil has been disturbed.
Dandelion is one of the harder weeds to control. It has a deep taproot and the leaves form a rosette close to the ground. This makes it hard to control by mowing. Hand-pulling is possible, but if you leave part of the tap root, the plant will grow back. After the dandelion flower head dries out, the seed-bearing “puff-ball” is scattered by the wind or by people making wishes and blowing on it. Each of these parts floating away are seeds. To control these weeds, either hand-pull them or use a herbicide.
To control henbit, chickweed and dandelion, the best products contain 2,4-D, dicamb and MCPP or MCPA. If using a herbicide, make sure it is labeled for the grass that it will be applied to, and always read the label. Products such as Weed-B-Gon Max and Trimec can be used at the recommended rates according to the label on Bermuda and Zoysia grass.
For Centipede and St. Augustine, look for products recommended for “Southern lawns” or read the instructions on the label.
The best cultural practice for controlling any of these weeds is to remove the plant early. There is an old saying that if you allow a weed to go to seed, you will be fighting that weed for the next five to seven years.