Prepared by Joey Williamson, HGIC Horticulture Extension Agent, Clemson University. Revised by Joey Williamson HGIC Horticulture Extension Agent, Clemson University. (New 12/08. Revised 11/09. Pesticides Updated 09/10.)
Has your lawn been invaded by a weed that goes to seed in early summer with white, fluffy, dandelion-like seeds? This invasive, winter annual weed is Facelis retusa, or annual trampweed. It’s been in South Carolina for decades, but with decreased annual rainfall in recent years, this highly competitive weed is colonizing any bare spaces in drought-stressed and low-fertility lawns and roadsides.
Annual trampweed (Facelis retusa)
Joey Williamson, Clemson University HGIC
Annual trampweed is a low-growing, broadleaf weed with narrow, alternate foliage. The upper leaf surface is a dull green, and the lower surface has white tufts of long hairs. The plant has freely-branching stems that have a prostrate and spreading habit.
To significantly control annual trampweed in lawns, homeowners must improve growing conditions for their lawns. A healthy and thick lawn will out-compete annual trampweed, and shade the soil to reduce trampweed seed germination in the fall. Proper turfgrass care includes taking a soil sample, applying the correct amount of dolomitic limestone to adjust the soil pH for optimum grass growth, and fertilizing the grass at the correct times with the appropriate lawn fertilizers (see HGIC 1201, Fertilizing Lawns).
With the reduced rainfall levels in recent years, turfgrass may need supplemental watering. Under most conditions, lawns in South Carolina require rainfall to be supplemented with irrigation for a total of one inch per week (see HGIC 1207, Watering Lawns). Implementing the proper mowing height for your turfgrass species is also important to maintain a thick grass stand (see HGIC 1205, Mowing Lawns).
If allowed to go to seed, one can reduce annual trampweed spread culturally by using a bagger on the lawnmower to catch the seeds along with the clippings.
By the time annual trampweed makes its fluffy, white seed heads in early summer, it is too late to use post-emergence chemical control.
Weed Control in Warm-Season Turfgrass: In warm-season grass lawns (such as bermudagrass, centipedegrass, St. Augustinegrass and zoysiagrass), a broad-leaf weed killer (post-emergence herbicide) should be applied in November and again in February, if needed.
A 3-way, broadleaf herbicide that contains 2,4-D, dicamba, and mecoprop (MCPP) will control annual trampweed. Examples of herbicide products with these ingredients are Bayer Advanced Southern Weed Killer for Lawns, Spectracide Weed Stop 2X Weed Killer for Lawns, Southern Ag Lawn Weed Killer with Trimec®, Lilly Miller Lawn Weed Killer, and Ferti-lome Weed-Out Lawn Weed Killer with Trimec®. These are liquid concentrates that are mixed with water in a pump-up sprayer and sprayed on broadleaf weeds in the lawn. Follow the directions on the product label for application rate for the turfgrass species and safe use.
Always follow the product label for application rates and safe use. Notice on the product labels that for use on centipedegrass or St. Augustinegrass, a reduced rate of herbicide should be used. Applications of these herbicides will kill any trampweed seedlings that germinated in the fall and those that germinated in the late winter. Do not apply broadleaf weed killers to any warm-season lawns during turfgrass green-up in the spring, as they may severely injure the lawn.
Alternatively, atrazine may be used for annual trampweed control, but only on centipedegrass and St. Augustinegrass. Apply atrazine to annual trampweed in November and again in February, if needed. A maximum of two applications per year is permitted. Do not apply atrazine during the spring green-up of these warm-season turfgrasses as significant injury to the lawn may occur. Examples of home lawn products containing atrazine are Southern Ag Atrazine St. Augustine Weed Killer, Hi-Yield Atrazine Weed Killer, Spectracide Weed Stop Concentrate for St. Augustine & Centipede Lawns, and Image for St. Augustine & Centipedegrass. Follow the directions on the product label for application rate and safe use.
Weed Control in Cool-Season Turfgrass: In tall fescue lawns that are typically over-seeded annually in October to maintain a thick grass cover, the application of a 3-way, post-emergence, broad-leaf weed killer (see examples above) should be delayed until February and then applied again in March. This will kill the trampweed plants from seed that germinated during the fall and spring. The early fall application is not made because this type of herbicide can injure tender, young fescue seedlings.
Alternatively, herbicides containing triclopyr may be used on tall fescue lawns to control annual trampweed. Make applications in February and again in March. Examples of products containing triclopyr for fescue lawns include Ortho Weed-B- Gon Chickweed Clover & Oxalis Killer for Lawns, Hi-Yield Turflon Ester Specialty Herbicide, and Ortho Weed-B-Gon MAX Concentrate Kills Weeds Not Lawns (this last product also contains 2,4-D and dicamba). Follow the directions on the product label for application rate and safe use.
Product Labels & Safe Use: In choosing a lawn weed killer, be sure to look at the product label. It will state onto which lawn species the product can safely be applied and which weeds will be controlled. Many consumer brands have several products with very similar names. A particular product may come in as many as three different forms: a concentrate to put into a pump-up sprayer, a ready-to-spray container with built-in sprayer, and a hose-end container that attaches to the garden hose. Sometimes the active ingredients are different in each of the three product forms. The best advice is: read the label for the active ingredients in the product, look for the weed to be controlled on the label, and make sure it can be used safely on your lawn species and at what time of year.
Remember that your trees and shrubs are broad-leafed plants, and all of the above herbicides can injure or kill them. Most deciduous trees and shrubs have lost their leaves by November and will not have leafed-out again by early March, so applications during these late fall and winter periods are less likely to affect them. However, do not spray heavily around the root zones of these ornamentals, as many herbicides can be taken up by plant roots. Fortunately, annual trampweed seems to be worse in most cases out in sunny areas of the lawn and far enough from trees and shrubs to not be a problem.
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This information is supplied with the understanding that no discrimination is intended and no endorsement by the Clemson University Cooperative Extension Service is implied. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.