Slit seeding is an efficient and effective way to overseed a lawn. It offers homeowners a tried and tested alternative to sowing grass seed by hand that is proven to transform thin, patchy grass into a thick, beautiful lawn.
Slit seeding a lawn can be done in fall or spring to repair and revitalize lawns. It ensures better seed-to-soil contact and improved germination rates compared to sowing by hand, however, it does require specialist equipment and may not be suitable for every type of lawn.
To help you decide if this technique should be on your lawn care plans, this guide looks at why and when to consider slit seeding a lawn. It also includes tips from experienced lawn care professionals and a step-by-step guide to slit seeding a lawn successfully.
What is slit seeding a lawn?
Slit seeding is a modern method of overseeding a lawn which offers the benefits of improved germination rates compared to spreading seed over the surface with a spreader or by hand.
Using a specialized slit seeding machine, small grooves are made in the soil and grass seed is dropped directly into the openings. By placing it into the pre-made slit the seed has better contact with the soil and is sowed at the ideal depth, there is no risk of the seed sitting on the thatch layer and not reaching the soil.
As it plants the grass seed into the groove, it also means a reduced risk of the seed drying out on the surface and eliminates the need to use measures to stop birds eating the grass seed.
There are several different scenarios where you can take advantage of the way slit seeding significantly improves germination rates to help get a green and thick lawn.
Sarah Jameson, the founder and owner of Lawn Chick, says: ‘I find that slit-seeding is particularly useful for repairing lawns with bare spots or thinning grass, as it ensures even distribution of new grass seed, eliminates the need to top-dress with straw or compost, and prevents seed from washing away in those bare or thin areas.’
Sarah adds that slit seeding is best suited for gardens with flat and open lawn areas, rather than small lawns with ‘lots of obstacles and tight turn areas’. Aeration before seeding is recommended on compacted lawns, and very weedy lawns will need controlling before seeding.
Sarah Jameson is the founder and owner of LawnChick.com, a trusted lawn care blog that educates millions of homeowners each year to help them achieve the greenest, healthiest lawn. Sarah’s blog is read by over 2 million homeowners each year.
When to slit seed a lawn
The best time for slit seeding a lawn will depend on your region and the type of grass seed for overseeding you use.
Mark Marino, the owner and operator of Lawn Phix in Massachusetts, explains why late summer into early fall, between late August and early October, is the best time to slit seed cool-seasons lawns with fescue, bluegrass, or ryegrass seeds.
‘The soil temperatures are warm enough for quick germination, while the cooler air temperatures reduce heat stress and diseases in new seedlings,’ says the lawn expert. ‘Slit seeding in the fall gives new grass plenty of time to develop a strong root system before winter dormancy. It's also the ideal environment for the lawn to recover from this process.’
When slit seeding a lawn with warm-season grasses, such as Bermuda grass, zoysia, or Buffalo grass, Sarah Jameson recommends doing so in late spring to early summer. She says: ‘April to June is best when soil temperatures reach at least 65°F, ensuring optimal germination.’
The perfect conditions for slit seeding a lawn include daytime temperatures between 60-75°F and soil temperatures above 50°F, as well as moist but not saturated soil to help the lawn slit seeder cut clean grooves in the ground.
Mark Marino is the owner and operator for Lawn Phix in the state of Massachusetts. He is passionate about nurturing soil health and optimizing turf nutrition, creating an ideal environment for grass to thrive
How to slit seed a lawn - 4 expert-recommended steps
You can rent lawn slit seeders from local equipment rental shops. Preparing the lawn beforehand is important, as well as familiarizing yourself with the machine to ensure you set up and use it correctly.
If you are unsure about using the machine, get professionals who are highly experienced when it comes to slit seeding a lawn. However, if you do want to do it as a DIY gardening project, the following four steps are crucial to success when slit seeding a lawn.
- Mow the lawn short - head out with the lawn mower and reduce the height of your lawn before slit-seeding. Cut your grass to 1.5-2 inches and this will improve the seed-to-soil contact
- Mark any underground objects - an important step before taking out the slit-seeding machine to reduce damaging and potentially costly mistakes. Sarah Jameson advises: ‘Mark any underground utilities, shallow tree roots, sprinkler heads, and irrigation lines. Since a slit seeder cuts into the soil you don’t want to damage your rented machine or utilities on your property.’ Also, remove any stones or sticks from the lawn to avoid damaging the machine
- Seed in a crisscross pattern - Do two passes with the machine for even coverage. Go in one direction (north to south) across the lawn, then make a second pass in the opposite direction (east to west). By doing two passes, if you miss a patch on the first run, you’ll hit it on the second. ‘When seeding in this way, you’ll want to calculate the amount of seed you need, and apply half of that seed when travelling up and down your lawn, and the second half when travelling back and forth,’ advises Mark Marino. ‘This way your coverage and the amount of seed is spot-on.’
- Have a post-seeding plan - The experts advise to fertilize the lawn with a starter fertilizer immediately after slit seeding. Also, they say to water the lawn regularly to keep it consistently moist for 2-3 weeks and avoid any foot traffic for the first two weeks.
This Turf Builder Starter Food for New Grass is designed to be used when planting new grass seed. It contains valuable nutrients to help the new grass develop strong roots and grow into a thick, green lawn. A perfect starter fertilizer for when overseeding or starting a new lawn from seed.
FAQs
Can you slit seed over existing grass?
Slit seeding is ideal for thinning lawns with bare patches, but not always for well-established lawns where the grass is already thick and healthy. In this scenario, overseeding the lawn with a broadcast spreader, available at Amazon, can be sufficient as there is a risk that slit seeding may damage the roots of the existing grass.
Chrissie Handley, lawn care specialist at Online Turf, says slit seeding a lawn with thick established grass is possible providing you take precautions. ‘You will need to make sure the machine is in tip-top condition, with sharp blades and a correct blade height setting, to make sure it does not rip, pull or damage your existing lawn,’ she says.
‘You may find that just sowing the seeds by hand and sprinkling some topsoil over the top does the same job of protecting the seeds, without the risk of ripping your lawn,’ adds Chrissie.
Chrissie Handley is Lawn Care Specialist providing tailored advice on laying, maintenance and general lawn care for Online Turf.
Overseeding is one of many important lawn care jobs to do in spring to get your grass in the best shape possible and able to withstand lots of usage during the warmer months.
Along with aerating, scarifying, feeding, and starting to mow in spring, taking time to give your lawn some TLC in spring will stand it in great stead for the rest of the year.
For more information, see our guide to spring lawn care and get tips for all those essential seasonal tasks.
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