Did you have weeds in your lawn last year?
I sure did.
One of my resolutions is to gain control of the weeds in my bahiagrass lawn. Common weeds that invade Florida lawns include heartleaf drymary and crabgrass.
Heartleaf drymary is one of my least favorite weeds because its sticky seeds get all over my dog’s furry paws.
Crabgrass is another difficult weed to control. There are few options once it grows in the lawn.
Post-emergence herbicides work on established weeds, but some may harm existing landscape plants or turfgrass.
For example, there are no effective post-emergence controls for weeds such as crabgrass in most lawns. You could spot treat with a product such as glyphosate, but you would need to use care not to spray the turfgrass, as it can injure your turf.
Additionally, post-emergence herbicides offer no protection against future weeds
However, there’s another option in the weed control toolbox: pre-emergence herbicides.
These herbicides can help reduce the amount of summer weeds because they are applied before weeds grow and seeds sprout. They work because they prevent or inhibit the weed seeds from sprouting or germinating.
These products are not a magical fix to apply throughout the year. If you want to get a handle on weeds before they grow, you must apply pre-emergence herbicides in late winter or early in the year.
Timing is critical.
If applied too late, they won’t work, and they will be a waste of time, money, and product.
The general rule of thumb is this: apply pre-emergence herbicides in Central Florida around mid-February — Feb. 15 is a date often recommended, but technically, they should be applied “before soil temperatures remain above 50°F for 24 consecutive hours.”
In addition to initial treatment, it’s very important to make a follow-up application within 60 days of the initial treatment.
To find a pre-emergence herbicide suitable for your lawn, first identify your type of grass (St. Augustinegrass, bahiagrass, zoysiagrass or Bermudagrass). Next, look for the active ingredients listed under pre-emergence herbicides.
When you visit the garden center, check product labels for one of these active ingredients. Local nurseries, hardware stores, feed stores and professional landscape supply companies may carry these products. Be sure to read and follow product labels.
Remember, hand-pulling weeds is always an option.
Be sure to practice good landscape management practices to reduce weeds. These practices include to provide your lawn the right amount of irrigation (but not too much because weeds love water), apply fertilizer appropriately (but not too much because weeds love fertilizer), and mow your lawn at the recommended mowing height.
Did you know that proper mowing is one of the most important things you can do to improve the health of your lawn? Correct mowing heights for turfgrasses:
Regular cultivars of St. Augustinegrass 3.5 inches to 4 inches
Dwarf cultivars of St. Augustinegrass 2.5 inches
Bahiagrass 3 inches to 4 inches
Zoysiagrass 2 inches to 2.5 inches
Bermudagrass 0.5-inch to 1.5 inches
If you have trouble identifying a weed, contact your local Extension office for help.
You may learn how to take care of your grass by visiting University of Florida’s online library at Edis.ifas.ufl.edu. Type the name of your grass, for example St. Augustinegrass, in the search box to get a list of publications.
Pre-emergence herbicides may save you time and money by preventing those weeds from sprouting. I hope you, along with me, get a handle on our lawn weeds this year!
References:
Telenko, D.E.P., R. Leon, and J.B. Unruh. (2016). Crabgrass Biology and Management in Turf. IFAS Publication Number ENH 1134. Gainesville: University of Florida Institute of Food and Agricultural Sciences. Retrieved from http://edis.ifas.ufl.edu/pdffiles/EP/EP39500.pdf
Trenholm, L.E., J.B. Unruh, and J.L. Cisar. (2015). Mowing Your Florida Lawn. IFAS Publication Number ENH 10. Gainesville: University of Florida Institute of Food and Agricultural Sciences. Retrieved from http://edis.ifas.ufl.edu/pdffiles/LH/LH02800.pdf
For additional information, email , or call (813) 744-5519, ext. 54145.
More information is available on crabgrass control and the time to apply pre-emergence herbicides, by going to this link: tinyurl.com/yd3zy2zg. The document lists various turfgrasses we grow in Florida and the pre-emergence herbicides available for each type of grass. These herbicides are listed by their active ingredients, not brand names.
Nicole Pinson is the Urban Horticulture Agent in Hillsborough County.
Published January 17, 2018
