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.
As a boy I remember our St. Augustinegrass lawn. I fondly remember winter annual weeds in that lawn.
Many of these so called “weeds” are native wildflowers. And a number of pollinators use these wildflowers.
To see clumps of winter annuals in our yard and in neighbors’ yards was a natural part of the transition from winter to spring. They added interest to the lawn. It was expected to see henbit with its square stiff stems holding up a display of small pinkish purple flowers in late winter to early spring. A clump of henbit was a great place to hide an Easter egg, especially a pink or purple one.
A pink Easter egg hidden in a mix of clover. Photo Credit: Larry Williams, UF/IFAS Extension – Okaloosa County
Wild geranium offered another good hiding place for eggs with its pink to purple flowers. Large clumps of annual chickweed would nicely hide whole eggs. Green colored eggs would blend with chickweed’s green leaves.
Crimson clover with its reddish flowers, hop clover and black medic with their bright yellow flowers provided good hiding places for Easter eggs. Plus, clovers add nitrogen back to our soils.
A yellow Easter egg hidden in a mix of clover. Photo Credit: Larry Williams, UF/IFAS Extension – Okaloosa County
The lawn was healthy and thick enough to limit summer weeds. But during fall and winter, as the lawn would naturally thin and go dormant, these winter annuals would run their course.
I remember the clean smell of freshly mowed grass in spring with the first mowing. Once mowed and as the heat took its toll, by late April or mid-May, these winter annuals were gone. What was left was a green lawn to help cool the landscape as the weather warmed. The lawn was mowed high as St. Augustine should be, watered only occasionally during dry periods, played on and typically not worried with.
Most lawns have winter annuals that let us know spring is near. Perhaps we worry too much with these seasonal, temporary plants that may have wrongly been labeled as weeds. Besides, how long have we been doing battle with them and they are still here. Most lawns have winter annual seeds that await the cooler temperatures and shorter days of early winter to begin yet another generation. By May they are gone.
UF/IFAS Extension agents in the Florida Panhandle are asking you to join in on “No Mow March” in 2023. The idea is to holdup on mowing until the calendar flips to April, allowing pollinators to enjoy these common winter annuals.
Here is a website with more information on No Mow March. On this site, you’ll find a link to sign up to be a participant, check out what Okaloosa and other counties are doing by clicking on “Events” and see more about pollinators, all on this site.
Need an excuse to not mow your lawn this month? UF/IFAS Extension agents in the Florida Panhandle are asking residents to skip their soon-to-be-weekly outdoor chore until the calendar flips to April.
The idea for “No Mow March” is borrowed from “No Mow May,” a concept begun in the United Kingdom that has now spread to northern parts of the United States.
“Obviously, our lawns are growing way too quickly by the time May rolls around,” said Beth Bolles, UF/IFAS Escambia County horticulture agent who is leading the pilot effort this year. “Here in North Florida, March is our transition period, when grass is exiting dormancy. But it’s also when pollinators are starting to become more active, so it’s the perfect time to celebrate them and promote their health and habitat.”
Bolles is quick to point out, though, that the month is about more than just turf.
“We recognize that some communities have rules to follow regarding their lawns,” she said. “There are other things you can do to encourage pollinators to visit, whether it’s container plants or adding new shrubs or pollinator houses. We encourage everyone to find their own way to participate.”
The first step in participating is to sign the pledge at go.ufl.edu/NoMowMarch. Visitors can also use the website to find virtual or in-person events geared to the topic, learn tips for adhering to homeowners association guidelines while still promoting pollinators, and record observations to a No Mow group on iNaturalist.
