Soil Temperatures & Importance of Timing Pre-Emergents

As the new year rings in, it becomes imperative to apply pre-emergent herbicides to your lawn. A pre-emergent is a herbicide that is intended to prevent weeds before they have the chance to start developing. Weeds begin to germinate at soil temperatures around 60 degrees Fahrenheit, so it is key that you apply the first pre-emergent when your soil has consistently reached 55 degrees; making the best time of year for application in the Fall and Spring. 

Hi-Yield Weed & Grass Stopper

According to Mr. Graham Simmons, director of Turfgrass Operations at Woerner Farms in Foley, AL, timing is critical because “once the temperature is right for weed seed germination you are “fighting from behind.” Pre-emergents work by preventing weed seeds from germinating or killing the seed shortly after it germinates, subsequently preventing it from becoming a full-grown plant. 

If you are new to lawncare and are not sure what product to use, we can offer suggestions. The best pre-emergents include Hi-Yield Weed & Grass Stopper, Sta-Green Crab-EX, and TURFGRO Professional (the latter two of which can be purchased at your local Lowe’s). Many pre-emergents are mixed with a nitrogen fertilizer, which can be problematic for your plants when nitrogen works with spring frost to cause harm. The aforementioned pre-emergents do not contain nitrogen and are therefore our favorite picks. We recommend a 0-base nitrogen product. 

Sta-Green Crab-Ex Crabgrass Control

Furthermore, Mr. Simmons recommends applying a post-emergent separate from the pre-emergent for winter weeds. Some chemicals like Atrazine have both pre and post emergent control.

In order to maximize the potential for your plants to thrive in your environment, you should consider the USDA growing zone map. This map sets the standard by which gardeners and growers can determine which plants will grow best in their location. The map takes the average annual minimum winter temperature and divides these into 10 degree Fahrenheit zones, which correlate to colors on the map. Compare these temperatures to those at which your plant will thrive.

You can also use https://www.greencastonline.com/tools/soil-temperature to determine your location’s soil temperature by location.