The continued hot, dry weather is stressing many plants. This weather also is keeping winter weeds from germinating.
But as soon as the weather changes into more fall-like conditions, the weeds will germinate. Start planning a weed-control strategy for lawns so germinating weed seeds die a fast death.
Three weeds cause the most problems in the winter: annual bluegrass, henbit and chickweed. These weeds come back from seeds each year, so use pre-emergence herbicides to control them. To do a better job, learn more about their life cycle and the conditions they grow in.
Annual bluegrass causes the most problems in lawns. The scientific name for this weed is Poa annua , but most gardeners call it po anna. This weed is a yellow-green color and in the spring has a silver-colored seed head. It seems to appear during the night in early spring, though 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 and high amounts of nitrogen. This weed is found more in Bermuda grass and zoysia lawns.
This is one weed that can be reduced by proper management of the turfgrass. The lawn can be aerated to reduce compaction. Also, this allows the excess moisture to move easier through the soil. Another way to reduce the excess moisture is to water the grass only when needed. This means watering deep once each week instead of applying smaller amounts of water more often.
Also, proper fertilization is important. 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.
Henbit is a weed that 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. Also, it likes areas that have been disturbed.
The third weed is chickweed, which is a mat-forming weed that has small, oval-shaped leaves, arranged opposite each other on the stem. Chickweed flowers are small, white clusters on the end of the stem.
Like henbit, chickweed likes areas where the turf is thin and the soil has been disturbed.
One of the cultural practices that can be used to control these weeds is to remove the plant before it goes to seed. There is an old saying that if a weed goes to seed, it will be a problem for seven years.
One of the best ways to control these weeds is to use pre-emergence herbicides. These weeds will start to germinate when the air temperature reaches 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, pre-emergence herbicides need to be applied by the second week of September. With the weather conditions this year, this time can be moved back to the first week in October. Henbit and chickweed also can be controlled by pre-emergence herbicides.
Most pre-emergence herbicides can be used on all 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. Scotts 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.
Charles Phillips is a retired Columbia County Extension Service agent and operates Hort Consulting. He can be reached at firstname.lastname@example.org.
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