Here's When To Start Your Spring Grass Seeding

Spring planting is a race to get your grass seed germinated and into adulthood before they face off with summer heat and weeds. That means the earlier you can get grass seed in the ground, the better. In fact, the Purdue University Turfgrass Science Program recommends seeding as early in the spring as possible to minimize competition with crabgrass and existing turf. But identifying exactly what that date is can be tricky. Geographic location, soil temperature, and even shade all factor in to choosing the optimal date for planting grass seed. Ahead, we break down how to determine when it's time to start your spring seeding.

Soil Temperature

Most people pay attention to air temperature when planning their spring grass seeding. And while that’s certainly important, it's the soil temperature that has the most impact. That’s because grass seed needs soil to be a certain temperature to grow. According to the Purdue University Turfgrass Science Program, cool season grasses like fescue, Kentucky bluegrass, and rye grass, need soil temperatures that are consistently above 55 degrees Fahrenheit to germinate. 

How to Determine Soil Temperature

Taking your soil’s temperature doesn’t require any fancy tools. In fact, you can use a standard meat thermometer. Push the thermometer into the ground to a depth of about 2-4 inches and leave it for about 5 minutes to acclimate. Take the temperature in the morning between 8 am and 10 am so it’s not affected by the sun heating the soil or overnight cooling. 

Air Temperature 

While soil temperature is critical, air temperature is still important. Air temperatures should be between 60 to 75 degrees Fahrenheit during the daytime while nighttime temperatures should ideally hover between 45 degrees and 55 degrees Fahrenheit. Air temperatures in this range will help stabilize soil temperatures, ensuring a higher percentage of your seeds germinate. 

Related: Don’t Wait for Spring: How to Start Seeds Indoors Now for a Healthy Garden

Location

The climate in which you live largely determines when that window for spring planting opens:

• The North: If you live in the northern half of the county (Pennsylvania, Michigan, Ohio, New York) you're looking at a later window of mid April to Mother's Day, which is typically when soil temperatures rise above 50 degrees Fahrenheit. 

• Transition Zone: Spring seeding starts earlier in that transition zone band that runs across the middle of the country and includes such states as North Carolina, Virginia, Kentucky and Missouri. If you live in one of these states, soil temperatures will warm earlier. You can typically begin your spring grass seeding between late March and Mid April. 

• Warm Season Lawns: if you’re growing warm season grass, such as Bermuda, St Augustine, or zoysia, soil temperatures need to reach 65 to 70 degrees Fahrenheit, which won’t happen until late May or June. 

Keep in mind that these windows are broad as the arrival of spring weather can vary by several weeks from year to year. A cold year, for example, could push your mid April planting plans into May. 

Related: The Best Grass Seed for Clay Soil and How to Prep Your Lawn for Planting

Other Plants

If you don’t like the thought of sticking your meat thermometer in the ground and want more clarity than a broad calendar offers, try using other plants to gauge your seeding timing. Forsythia bushes bloom when soil temperatures reach about 55 degrees Fahrenheit, so they serve as a great indicator of when it’s time to plant cool season grass seed. Blooming redbuds are also a sign that the peak seeding window is open. 

Shade 

Soil temperatures will stay cooler in the shade than it will in an area that gets direct sunlight. If you’re seeding in a shady area, wait an extra week before putting down seed to give the soil a chance to warm up. 

Wet weather 

While soil and air temperature are key, you also need to keep an eye on precipitation. Gentle spring rains are fine, but a heavy deluge the day after you seed will wash all that expensive seed away. Check the weather and avoid planting if storms are in the immediate forecast. 

While You’re Waiting

Get your yard ready, so you can lay seed as soon as temperatures reach that just right level. Remove any excess thatch from the lawn. Loosen up the soil with a rake to promote good seed to soil contact, which will improve germination rates.