We have begun our sprinkler start-up season! Below is some information that we often receive questions about this time of year related to planting soil temperatures and our growing season in Wisconsin. We had a nice sunny weekend with warm temperatures, but cool temperatures are still ahead, with below freezing temperatures forecasted for the weekend. Our soil is currently still below 50 degrees in most areas. We are typically starting systems in our service area each spring from about Mid-April through the end of May to correspond with the average growing seasons in our area.
What temperature should the soil be for growing?
Knowing the soil temperature is important for many activities including agriculture and horticulture. The soil temperature is different from the air temperature.
A SOIL temperature of fifty degrees Fahrenheit is a good benchmark for cool-season crops and sixty degrees for warm-weather plants like peppers and basil, and ideally 65-70 degrees for tomatoes.
Cool-season grass seed germinates best when soil temperatures reach 50 to 60 degrees Fahrenheit. This corresponds to consistent daytime air temperatures in the 60-to-75-degree range.
How cold is too cold for soil?
Planting in cold soil (below 50 degrees) when cold conditions are expected for the next 48 hours can lead to germination problems and seedlings not emerging or not emerging well.
What temperature kills grass seed?
If you are wondering how cold is too cold for the grass seed germination, a good rule of thumb is if the daytime temperature is below 60 F, then soil temperature is below 50 F, making it too cold. If there is frost or still a danger of frost, then it is too cold.
In our service area of Wisconsin, the growing season ranges from mid to late May through about mid to late September. For example, the current average growing season average is:
Vilas County: May 27 through Sept 21
Marathon County: May 12 through September 29
Source: mrcc.purdue.edu, Midwest Regional Climate Center (MRCC)
An inexpensive soil thermometer available at garden stores can help eliminate the guesswork. It is important to measure to the root depth (4” recommended), not just the surface level. Online sources can also be helpful, such as the National Weather Service or data from MRCC to help guide your planting.
Visit www.mrcc.purdue.edu/clim/Soil-T or www.greencastonline.com/tools/soil-temperature to see the average date for your area when soil temperatures warm above 50 degrees Fahrenheit or to check your specific location.
For our current Green Lawn customers, we automatically schedule your start-up service each spring and contact you about a week in advance of the date to confirm, so you know when to expect us. We start south of Wausau and work our way to northern Wisconsin, as we correspond our work with the Wisconsin growing season.