Key Points
Slit-seeding is an overseeding method that uses a machine to cut grooves and simultaneously add grass seed to a lawn.
Slit-seeding prevents birds or pests from removing the seeds, or wind or rain from blowing or washing them away.
Slit-seeding is best for extremely thin and struggling lawns.
Grass lawns occasionally must be overseeded to strengthen root systems and crowd out weeds. Slit-seeding is an effective method of aerating and overseeding a lawn. But it isn’t for every lawn and can damage some lawns.
Read on to hear what lawn and turf experts say about the benefits—and potential dangers—of slit-seeding a lawn.
Meet the Expert
Brian Feldman is Senior Director of Technical Operations at TruGreen.
Chrissie Handley is a Lawn Care Specialist at Online Turf.
Jason McCausland is Technical Coordinator at Weed Man.
What Is Slit-Seeding?
Slit-seeding, or slice-seeding, is an overseeding method that uses a machine to cut grooves and simultaneously add grass seed to a lawn.
Slit-seeding allows grass seed to be deposited directly into the grooves, ensuring good seed-to-soil contact for improved germination and growth, says TruGreen’s Brian Feldman.
A slit-seeding machine is about the size of a large lawn mower. Vertical discs about 1-inch apart groove the turf. A hopper holds the grass seed and dispenses it behind the discs.
How Slit-Seeding Is Done
Slit-seeding a medium-sized lawn can be done in a day or two. The job requires an overseeding (or slit-seeding) machine, a mower, and a rake.
Measure the lawn: Measure the lawn’s area (length multiplied by width) and buy the correct amount and type of grass seed.
Clear out the lawn: Remove rocks, twigs, and other obstructions, and be sure to mark sprinkler heads.
Mow the lawn: Mow the lawn short—about 1 to 2 inches high.
Fill the hopper: Pour grass seed into the machine’s hopper.
Adjust the machine: Adjust the cutting depth of the discs and the seeding rate.
Pass in perpendicular directions: Slit-seed the lawn in parallel rows in one direction with half of the grass seed. Slit-seed perpendicular to the first rows with the remainder of the grass seed.
Smooth out the thatch: Smooth over some of the grass thatch with a rake. Dethatch excess thatch.
Advantage of Slit-Seeding
«The main appeal of slit-seeding is that you’re ensuring the seeds are making direct contact with the ground,» says Chrissie Handley, a lawn care specialist at Online Turf.
This minimizes the chance of birds or pests removing the seeds or wind or rain blowing or washing them away. Better-protected seeds can fully germinate and produce a healthier yield.
Best Slit-Seeding Conditions
«Slit-seeding is most commonly done where the lawn has started to thin, either from heavy traffic or lack of nutrients,» says Jason McCausland, with Weed Man.
It’s also a great way to fill in bare patches created by turf disease, insects, or pet damage, adds McCausland.
When to Avoid Slit-Seeding
Feldman emphasizes that slit-seeding is best for extremely thin and struggling lawns, as this method helps thin lawns regain density.
So, generally avoid slit-seeding on a well-established lawn, as the machine’s discs may mangle and destroy healthy grass and root systems.
While not always recommended, it is possible to slit-seed pre-existing grass, Handley says.
«You will need to make sure the machine is in tip-top condition, with sharp blades and a correct height setting.»
These precautions reduce the chance of ripping out or damaging an existing lawn.
DIY vs. Pro Slit-Seeding
While professional slit-seeding is usually recommended, slit-seeding is within the reach of many DIYers.
«DIY slit-seeding depends on your abilities and whether you want to spend the time doing it,» McCausland says.
Many rental yards rent overseeding machines for around $100 per day or $375 per week. Homeowners should take extra time to learn how to use the machine. Start slit-seeding in a remote location because of the potential for lawn damage.
Best Time for Slit-Seeding
The best time to conduct slit seeding for cool-season grass is in the fall, Feldman says. Cool-season grass includes varieties like Kentucky bluegrass, perennial ryegrass, and fescues.
«The soil remains at an ideal temperature to enhance seed germination, while the cooler air temperatures reduce stress on new grass,» he says. «This timing allows new grass to establish roots before the winter months.»
You can, however, also do slit seeding in the cooler spring months as well.
Feldman reminds homeowners that successful seed germination and establishment depend on proper watering and fertilization.