Weeds change with season
Fall is in the air.
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The mornings this past week were great. The cool temperature was a relief from the week before.
Just as our season is changing from summer to fall, the weeds in our landscapes are changing. I have had many people bring samples into the office, and these weed samples contain both summer and winter weeds.
As I look at my yard, I can find nutsedge and wild garlic growing side by side in my lawn. So what do I do now to control these weeds?
When you have summer weeds, there are a couple of things to help control them. If they are annual weeds, especially grassy weeds, you can mow them and catch the seeds that are being produced. This will remove some of the seeds that could germinate next year.
Some of the weeds are perennial and will come back next year. You can treat these with herbicides now to control them. The herbicide that you will use will depend on your type of grass. For Bermuda and zoysia grass, use a three-way product that contains 2, 4-D, MCPP, and Dicamba. These products will control most broadleaf weeds and can control wild garlic and onions. For centipede and St. Augustine grass, you can use atrazine.
Winter weeds need to be controlled before they germinate. The best way to control these weeds is to use pre-emergence herbicides. Winter weeds will start to germinate when the air temperature reaches 75 degrees.
However, research at Auburn University has shown that annual bluegrass can germinate as early as mid-September. So the best time to get your pre-emergence herbicides out is by the second week of September. However, it is not too late to do it now. The other major winter weeds, Henbit and chickweed, also are controlled by pre-emergence herbicides.
Most of pre-emergence herbicides can be used on all turfgrasses, and they give good to excellent control of the annual 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. It can be used on centipede and St. Augustine for pre- and post-emergence control. Scotts Bonus S also can 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.
The winter weed that I get the most calls on is Poa annua or annual bluegrass. This is a grassy weed that is a yellow-green color and in the spring has a 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.
Annual bluegrass likes areas that have wet, compacted soils and have high amounts of nitrogen fertilizer. We find this weed more in bermuda grass and zoysia lawns.
This is one weed we can reduce by managing our lawns. Aerate the lawn to reduce compaction. That allows water 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 a week instead of applying smaller amounts of water more often. Also, make sure that you don't apply more nitrogen than needed. 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 other weeds that we will have problems with are perennials, such as wild garlic and onions and dandelions. There are a number of ways to control these. The first is to pull or dig them up. If you are looking for a herbicide to control them, you can use the three-way products in Bermuda and zoysia, and you can use atrazine in centipede and St. Augustine. Another herbicide that works well on wild onions and garlic is imazaquin (Image). Read the label of the Image to make sure that the product contains imazaquin.
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