Winter weeds thrive on warm weather

One of the disadvantages of this unseasonably warm weather is that the winter weeds have had a big growth spurt.

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With the early cold weather, the weed growth was slower than in past years, but the weeds are making up for lost time.

There are a number of weeds that cause us problems. The ones that I get the most calls about are annual weeds such as annual bluegrass, henbit and chickweed. These weeds live one growing season, produce seeds and die. The seeds germinate in the fall, and the process starts over again.

The other group of weeds is perennials. These come back each year from the roots. But some plants start every year from seed. The No. 1 perennial weed is dandelion.

The first weed that we will discuss is annual bluegrass. You might hear someone refer to it as Poa annua or poor Anna. This is a grassy weed that has a yellow-green color and 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 as well.

Annual bluegrass likes areas that have wet, compacted soils. Also, it likes areas where high amounts of nitrogen fertilizer were applied.

We tend to find this weed more in Bermuda grass and zoysia lawns. This is one weed we can reduce by the way we manage our lawns. We can aerate the soil to reduce compaction. This allows the excess moisture to move more easily through the soil.

Another way to reduce the excess moisture is to water the grass only when needed. This means watering deep once a week instead of applying smaller amounts of water more often. Right now, we have had plenty of rain, so you don't need to have your irrigation system turned on.

Also, make sure not to apply more nitrogen than the grass needs. Bermuda grass needs 4 pounds of actual nitrogen per 1,000 square feet per year, and zoysia needs 2 to 3 pounds of actual nitrogen per 1,000 square feet per year.

The next weed is henbit, which 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 henbit 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.

The third weed is chickweed. 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. Mouse-ear gets its name from the grey-green leaves that are hairy. Chickweedlike henbit prefers areas where the turf is thin and the soil has been disturbed.

Dandelion is one of the hardest weeds to control in centipede and St. Augustine lawns. It has a deep taproot, and the leaves form a rosette close to the ground. This makes it hard to control by mowing. You can try digging this weed, but if you leave part of the tap root, the plant will grow back.

The leaves and stalk of dandelion exude a milky substance when broken, and kids have fun playing with the yellow flowers and puff-balls. When you hold a puff-ball up in the wind or you blow on it, the puff-ball breaks up and floats away. Each of these parts that are floating away are the seeds.

To control these weeds now, either hand-pull them or use an herbicide to control them. If using an herbicide, make sure it is labeled for the grass that it will be used on.

To control henbit, chickweed and dandelion, the best products contain 2,4-D, dicamb, and MCPP or MCPA. These products can be used at full strength on Bermuda and Zoysia grass. Most of the labels call for a half rate on centipede and St. Augustine. For control of henbit and chickweed, use atrazine.

For annual bluegrass control, also use atrazine. It will give post-emergent control of this weed, and you will get pre-emergent control for 30 to 45 days. Atrazine is labeled for use on centipede, St. Augustine and Zoysia grass.

If you are going to use atrazine on Bermuda, apply it in the next two weeks.

One of the cultural practices that you can use to control any of these weeds is to remove the plant before it goes to seed. There is an old saying that if you allow a weed to go to seed, you will be fighting that weed for seven years.

Columbia County Extension Agent Charles Phillips can be reached at (706) 868-3413 or by e-mail at charlesp@uga.edu. The Extension Web address is www.ugaextension.com/columbia.