If you’ve ever walked barefoot through a patch of burweed, you know this is a very unpleasant experience. Lawn burweed, also called spurweed or stickerweed, is a low growing winter annual that produces hard, spiny burs that contains the plant’s seeds. These burs or stickers make walking on grass extremely painful for not only people walking barefoot, but pets as well.
Lawn Burweed. Photo: Danielle Williams.
Dealing with lawn burweed can be tricky. Because lawn burweed is a winter weed, seeds actually germinate when temperatures are cool in the fall (late October-November). It then remains unseen during the cold months but as temperatures warm up in the spring, lawn burweed initiates a period of rapid growth and forms the spiny burs which may be hard to see but are easily felt. At this stage, the plant has set seed for next year and killing the remaining foliage won’t remove the burs. Moving forward, there are some things to consider.
Cultural Control
Burweed tends to be prominent in high traffic areas or areas where grass is declining so it is important to prevent infestations by maintaining a healthy, dense lawn. This can be achieved by fertilizing and liming according to soil test results as well as mowing at the proper height and frequency for your specific turfgrass. A healthy lawn can outcompete burweed for light, water, and nutrients and reduce the level of burweed infestation. For more information on maintaining your lawn visit: https://hort.ifas.ufl.edu/yourfloridalawn/
If burweed is only in isolated areas, you can always dig it up and dispose of it. Be sure to wear gloves and watch out for the stickers!
Chemical Control
Post-emergent control: Post-emergent herbicides are most effectively applied when burweed plants are young, actively growing, and haven’t set burs yet from December – February. Controlling burweed now is not impossible, but the burs have likely already formed and will remain present even after the weed dies. Additionally, since burweed is a winter annual, it will begin to die as temperatures reach 90 ◦F and above.
Look for herbicides containing the following active ingredients to help with post-emergent control:
Atrazine – sold under many brand names and safe in centipede, St. Augustine, and bermudagrass. Do not use in zoysiagrass or bahiagrass lawns.
Dicamba, mecoprop, 2,4-D – commonly sold in three-way formulations through many brand names. Generally safe in centipede, St. Augustine, bermuda, zoysia, and bahiagrass lawns.
Metsulfuron – sold under several brand names and safe in centipede, St. Augustine, zoysia, and bermudagrass. Do not use in bahiagrass. Be careful if used around ornamentals.
Thiencarbazone, iodosulfuron, dicamba. Safe in centipedegrass, zoysiagrass, bermudagrass, and St. Augustinegrass. Do not use in bahiagrass.
Pre-emergent control:If you are struggling with a lawn burweed infestation this spring, plan to do a pre-emergent herbicide application this fall. A herbicide containing the active ingredient, isoxaben can be used to control lawn burweed in centipedegrass, St. Augustinegrass, bermudagrass and zoysiagrass. In order for a pre-emergent herbicide application to be effective, it must be applied before the plant sprouts. For burweed, isoxaben can be applied in October or once temperatures fall to 55-60 ◦F and winter weeds begin to germinate.
Of course, before using any type of herbicide, always read the label instructions! If you have questions about lawn burweed control, please contact your local Extension Agent.
Spring is approaching and the main thing on my mind is controlling annual weeds. The most effective way to control crabgrass and other summer annual weeds is with a pre-emergent herbicide. Pre-emergent herbicides should be applied prior to weed seed germination. They don’t prevent germination, but they do prevent emergence of shoots and roots by forming a barrier on the soil surface.
Crabgrass growing in centipedegrass lawn. Photo credit: UF/IFAS Extension
Summer annuals such as crabgrass and chamberbitter begin to germinate when soil temperatures warm in the spring. Preemergence herbicides should be applied when daytime temperatures reach 65oF to 70oF for 4 or 5 consecutive days to form a barrier to help prevent these weeds from emerging. This is about the same time azaleas and dogwoods begin to bloom. Goosegrass is the exception for this temperature rule. For good goosegrass control, preemergence herbicides should be applied 3 to 4 weeks after the suggested daytime temperature application date.
It is important to note that you should only use preemergence herbicides on lawns that have been established for at least a year. These herbicides are prone to injure newly planted lawns. In addition, many preemergence herbicides may interfere with lawn grass seed germination, so make sure to refrain from reseeding for at least six after application.
Commonly available preemergence herbicides contain the active ingredients oryzalin, benefin, pendimethalin, DCPA and bensulide. However, there are a wide variety of products on the market. For more information on weed management please read the UF/IFAS publication “Weed Management Guide for Florida Lawns”.
Weeds can be the bane of the gardener’s existence and Extension Agents get a lot of questions on how to manage them throughout the year. Whether you are growing edibles, ornamentals, or turfgrass you have probably encountered a plant out of place which is basically the general definition of a weed. Just like with any other landscape challenge the first thing you need to do when dealing with weeds is accurate identification. Understanding the life cycle of the pest (weed in this case) you are targeting will be key for the most effective control with minimal inputs. Your local Extension office can assist with weed identification, and you can find a list by county here.
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We have one more episode of Gardening in the Panhandle LIVE! scheduled this year on October 12th. We hope you will join us for Herbs and Cool Season Edibles!
Weed control is never ending in Florida landscapes. If there is a bare area of soil, weeds take advantage of that void and make themselves at home. Ideally, we would use good cultural practices that minimize weed invasion, but if prevention is ineffective and you need to use an herbicide, make sure you are using that tool properly.
When I talk to homeowners and commercial applicators about weed control, many times they have selected the appropriate product but are still struggling with management. While troubleshooting the problem, many times I discover, the reason is related to poor uptake because the client is not making herbicide applications to what I like to call “happy weeds.”
When using an herbicide, you need to think about how it works. Not the deep level chemical reactions, but rather consider how the active ingredient is going to be delivered to whatever physiological function of the plant it is targeting.
Does the herbicide need to be absorbed by the leaves/stems/roots?
Once absorbed, does it need to travel through the vascular system of the plant (translocation)?
What effect will temperature, moisture, mowing/trimming have on product uptake?
All these factors are very important because if a plant is stressed, the primary response is survival. During excessively hot weather plants close off stomata, form waxier surfaces, and do everything they can to retain moisture – which also includes reduced absorption of herbicides. In cool weather, the plant may be dormant or have slowed growth that will reduce translocation.
Mowing and trimming reduces leaf surface area minimizing uptake. Overcoming injury also triggers the plant to go into water conservation mode which also limits product uptake.
So, what do I mean by “happy weeds”? For herbicides to be effective, they should be applied when growing conditions are ideal for your target plant. Optimum soil moisture, soil temperature, ambient temperature, and minimal stress lead to “happy weeds” that are primed to accept herbicides and translocate if needed. Plants in survival mode will have their defenses activated and this decreases herbicide efficacy.
Always read and follow entire label instructions of all pesticides.
Chamber bitter is a weed commonly found in Florida landscapes.
Photo by Beth Bolles, UF Extension Escambia County
Smilax is a common vine that can pop up in unwanted spots in landscapes. Learn about how this plant grows and management techniques with UF IFAS Escambia County Extension.
Do you have a low-growing weed that is producing tufts of white, fluffy, dandelion-like seeds, which float in the wind when disturbed or mowed? This is Annual Trampweed (Facelis retusa). I did not see this weed in North Florida until recent years. It’s native to South America.
Mid-April to early May is the time of year when this winter annual weed goes to seed in North Florida. That’s what it is doing now and it is a prolific seed producer. Each white tuft contains numerous seeds. Each tiny seed is attached to a small individual bristle, coming out of the larger tuft, which is carried by wind. This allows hundreds of seeds to move to other locations.
Trampweed is approaching the end of its life as we move into early May. As a winter annual, the individual weed dies in response to warm temperatures only to leave behind hundreds of seeds that survive the summer. These same seeds come up the following fall to early winter to begin the next generation. The best time to attempt chemical control with an herbicide is well before these weeds mature and begin flowering.
Trampweed in bloom. Credit: Larry Williams
One chemical control option is to apply a lawn preemergence herbicide during October when nighttime temperatures drop to 55° to 60°F for several consecutive nights. This will be just before these winter annual weeds emerge. Done correctly, the application of a preemergence herbicide forms a temporary chemical barrier along the soil surface preventing the winter annual weeds from emerging. Hence the name preemergence.
A second application of preemergence herbicide may be required six to nine weeks after the initial application to achieve season-long control, based on the product’s label directions.
If you miss this narrow window of opportunity to apply a preemergence herbicide, watch for the small young weeds in winter and treat then with a postemergence herbicide that is labelled for use in the type of lawn grass you are growing.
Waiting until trampweed is producing flowers and seeds in April and May to attempt control is almost worthless in controlling this weed. Correct timing is critical.
Trampweed usually is found in areas of a lawn that are already weak and thinning. It favors open, dry, stressed and low-fertility areas of a lawn. So, try to manage your lawn correctly. This involves learning to mow, irrigate and fertilize correctly for the type of lawn grass you are growing.
