Plant Solutions NJ Staff
Lawn seeding 101: The difference between slice seeding and overseeding
Updated: Mar 24
We’ve been driving home to you over the last few months that fall is a perfect time of year to plant. Whether you’re filling in those bare spots or putting in a whole new lawn, the cool nights and warm days will make those seeds green up into full-on sea of grass seemingly overnight. And here’s another secret: There’s more than one way to seed your lawn!
Your Seeding Options
You have two options for getting that lawn patched up to thicken the grass cover and create a healthy cover before winter comes: One option you’ve probably heard of and the other may be a new concept for you.
This is the option most people think of when laying down new grass seed. It entails using a cyclone or drop-seed spreader to distribute grass seed evenly over either an existing lawn, a prepared surface (see our post/information about installing an organic lawn from earlier this year) or literally sprinkling seeds by hand into gently raked bare spots in your lawn.
Overseeding an existing lawn can be way more labor intensive than slice seeding. This is because your lawn will require two to three rounds of aeration, preferably with a mechanical core-type aeration machine. Once the seeds have been broadcast, you’ll need to heavily water the area to wash those seeds into the aeration holes for better seed-to-soil contact (remember, seeds must be in contact with soil in order to start growing!). Even with this heavy watering, overseeding has an average successful germination rate of just 30%.
Pro Tip! If your thatch layer is more than a ½-inch thick, dethatch your lawn first to greater exposure of the soil.
Slice seeding (aka slit seeding):
You may not be familiar with slice seeding, but hopefully the words “80% germination rate” will grab your attention. The process involves a mechanical slit-seeder machine with vertical cutting blades. These blades cut through the thatch to create tiny furrows that will expose the grass seeds directly to the soil. The slit-seeder drops seeds into these furrows as it moves across the lawn. We do recommend two passes across the area with the machine at a 45° angle to create a cross-hatched pattern. This pattern results in better coverage and thicker growth. Another benefit of the slit-seeding machine is it generally requires less seed with the improved seed-to-soil contact to produce a lush lawn.
Whether you use the overseeding method or the slice-seeding method, the process should begin with testing your soil first. This will correct any issues that caused a weak, less-than-healthy lawn. The soil test will indicate how to improve and balance the soil’s pH, and a more balanced pH will result in a better germination rate. Give those seeds the best chance of survival before you get started with the whole process!
The proper steps for slice seeding success
What you really want to do is follow the three-step process for slice seeding. In our opinion, the ideal way to thicken and revitalize your lawn is this:
Apply a good compost
Going through this three-step process anywhere from September through the first week of November will give the seeds enough time to germinate and gain a great foothold in the lawn before the lawn goes dormant for the winter.