There is a season for everything. There is a time to plant and a time to reap, a time to be born and a time to die, a time to laugh and a time to cry.
Therefore, we need to be planning weed-control strategy for our lawns so the weed seeds that are going to be germinating (born) will die a fast death. If we can accomplish this, we won't be crying next spring when our lawns are covered in weeds.
There are three weeds that cause the most problems in the winter: annual bluegrass, henbit and chickweed. These weeds are annuals, which means they come back from seeds each year. So we can use pre-emergence herbicides to control them. In order to do a better job of controlling these weeds, we have to know more about their life cycle and the conditions that they like to grow in.
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 is a yellow-green color and, in the spring, has silvery colored seed head. They seem to appear overnight in your yard in early spring. However, they have been present since late September or early October. Some of the seeds will germinate in March also. Annual bluegrass likes areas that have wet, compacted soils and high amounts of nitrogen fertilizer applied. We tend to find this weed more in bermuda grass and zoysia lawns.
This is one weed that can be reduced by how we manage our lawns. We can aerate the soil to reduce compaction. Also, 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 deeply once a week instead of applying smaller amounts of water more often. Also, make sure that you don't apply more nitrogen than the grass needs. Bermuda grass needs four pounds of actual nitrogen per 1,000 square feet per year, and zoysia needs 2-3 pounds of actual nitrogen per 1,000 square feet per year.
The next weed is henbit. Henbit is 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, and areas that have been disturbed.
The third weed is chickweed. Chickweed is a mat-forming weed that has small, oval-shaped leaves. The leaves are arranged opposite each other on the stem. Chickweed flowers are small clusters on the end of the stem and are white. Chickweed, like henbit, prefers areas where the turf is thin and the soil has been disturbed.
One of the cultural practices that you can use to control 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. So, remove the weed before it goes to seed.
One of the best ways to control these weeds is to use pre-emergence herbicides. These weeds will start to germinate when the air temperatures reach 75 degrees. This is usually late September or early October. However, research at Auburn University has shown that annual bluegrass can germinate as early as mid-September. So, you need to get your pre-emergence herbicides out by the second week of September. Henbit and chickweed are also controlled by pre-emergence herbicides.
Most of pre-emergence herbicides can be used on all of our turfgrasses, and they give good to excellent control of these three weeds. Some of the products to use are benefin (Balan), pendimethalin (Halts), benfin plus trifluralin (Team), benefin plus oryzalin (XL), and prodiamine (Stagreen Crabgrass Preventer). Atrazine is another herbicide that can be used for control of these weeds. Atrazine, depending on the brand, can be used on centipede and St. Augustine for pre- and post-emergence control of these weeds. Scott's Bonus S can also be used on zoysia.
The secret to success with these products is to follow the directions on the label, and get the product out early enough to control the first weeds as they germinate.
Columbia County Extension Agent Charles Phillips can be reached at (706) 868-3413 or by e-mail at email@example.com. The Extension Web address is www.ugaextension.com/columbia.
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