Remember last summer’s hot, dry days and grass drying up and turning brown? Yet, weeds were green and doing fine. Those weeds flourished and dispersed seed everywhere. Now, they are just sitting there ready to sprout again.
It's time to start thinking about weed prevention. Every herbicide label warns against application when temperatures are above 85 degrees and especially under drought conditions. Pre-emergent herbicides must be applied before seed germination.
Late winter is the time to focus on summer annual weeds. The narrow window for application is challenging. Homeowners often wait too late into spring to put out preventive products.
A general rule of thumb for pre-emergent herbicide timing is Feb. 15 through March 1 in North Florida. However, weed seeds germinate in response to soil temperature, not calendar dates.
By monitoring daytime temperatures, one can determine a more effective application date. When there are four to five consecutive days that reach 65 to 70 degrees, weeds will germinate. This generally coincides with the first blooms appearing on azaleas and dogwoods. With a warm winter, it may occur as early as mid-January.
Some active ingredients in pre-emergent herbicides include dithiopyr, isoxaben, oryzalin, pendimethalin, prodiamine and simazine. Always read the label for the specific weed controlled and observe all directions, restrictions and precautions.
Weed and feed products that contain nitrogen are not suitable as pre-emergent herbicides. Irrigation is necessary before and after an application to activate these products. The chemical binds to soil particles, creating a barrier that remains effective for six to 12 weeks. Reapplication will be necessary for season-long control, especially with constantly fluctuating winter temperatures.
Now is the time to purchase pre-emergent herbicides and prepare to apply them. Go to http://edis.ifas.ufl.edu/ep141 for more information on weed control in lawns.
Sheila Dunning is an agent at the University of Florida's Institute of Food and Agricultural Sciences Extension office in Crestview.
This article originally appeared on Crestview News Bulletin: Plan to reduce summer weeds