Sometimes tending a lawn can be as complicated – if not more so – than tending a garden. One of the biggest issues occurs when your lawn has survived a lot of abuse the previous year and needs overseeding.
Overseeding grass in spring isn’t a complicated process by itself. It’s often a good time for adding fertilizer or contact herbicides when you have a busy schedule.
Perhaps the most confusing aspect is knowing at what temperature you should overseed. Spring often offers a narrow window of opportunity.
What Is the Best Temperature to Overseed in Spring?
The soil temperature needs to be at least 50° degrees Fahrenheit for cool-season grass and 60° degrees Fahrenheit for warm-season grass. Ensure the danger of frost is over.
This usually falls in late April or early May, depending on whether you have a cool-season or warm-season lawn.
The Great Spring Debate
Depending on who you talk to, you’ll either be encouraged to overseed in spring or told to avoid it at all costs.
Here is what you need to know before doing any overseeding a lawn in spring.
Why You Should Overseed in Fall : Fall Overseeding Temperature
The soil is often warmer than the air when fall first hits, giving a wide window for overseeding.
Warm-season grass needs even warmer temperatures. The seedlings can often be choked-out by crabgrass or other weeds when they would otherwise be able to sprout.
Meanwhile, cool-season grasses will go dormant in hotter summer temperatures. Thus, they might not have enough time to grow before the weeds come in.
There’s a large window in more southern zones in which you can overseed warm-weather grasses.
When To Spring Overseed Lawn and Grass
Use weed and feed or post-emergent herbicide to give your cool-season grasses a head start before the weeds take over.
In the northern zones, sowing warm-season grasses too late in the year can reduce their chances of germinating before the cold hits.
The Verdict
Spring overseeding is generally a good move if you have a cool-weather grass lawn and live in the north or northeast. But it is not a good choice if you have a warm-weather grass type and live in the south or southwest.
Best Temperature For Overseeding: Ground Temperature vs. Air Temperature
A common mistake people make when preparing to overseed is to look at the weather forecast and go by the air temperature.
Yet, determining soil temp for overseeding can be complicated since many factors (sun exposure, moisture, soil type, etc.) can affect it.
However, it’s possible to estimate the soil temperature in fall by looking at your weekly weather forecast.
It’s a little more complicated for spring. The best overseeding temperature is when the air temperature has been at least 59° degrees Fahrenheit for two weeks.
This will help ensure the ground temperature is at least 50° degrees Fahrenheit when you go to overseed cool-weather grasses.
Overseeding In Spring: An Overview
The overseeding process is much less complicated than figuring out the temperature or whether to wait for fall.
Here’s a quick rundown of the process to get you going:
Step 1: Mow
Cut the grass a little shorter than usual, then go over it with a rake.
This practice removes debris, dead grass, and clippings and loosens the topsoil.
Step 2: Fix Major Issues
Now is an excellent time to test the soil quality and make sure it’s pest-free and has no other significant problems.
It is also a good time to make sure any pre-emergent herbicides have mostly dissipated, as they’ll often also kill grass seed.
Once you’ve addressed pests, diseases, or other issues, move on to the next step.
Step 3: Amend the Soil
If you’re using pure seed, rake a thin layer of enriched soil over the existing lawn, but avoid adding more than ¼” inch.
You can skip this step if you’re using a seed mix with its own fertilizer or amendments.
Step 4: Overseed
Now you’re ready to sow the seed using your preferred spreader.
The best way is to cover your lawn in one direction (ex: east-west), then go back in the other direction (north-south).
Step 5: Water
Finally, water the lawn and (if you choose) fertilize it.
Be sure to water the lawn at least once per day until the new grass catches up with the rest of the lawn.