Late summer and fall are among the best times to plant grass seed and lay fresh sod for establishing before winter. For many plants, including grass, the season is ideal for setting roots with mild air and soil temperatures and regular seasonal moisture.

Whether opting for easy-to-spread seed or an instant lushness with sod, we’re in the sweet spot of lawn establishment now.

The biggest effort in planting a new lawn is in the all-important preparation. Laying the literal groundwork is key to successful rooting and healthy blades for seasons to come. Choosing topsoil and garden amendments to improve soil composition is the basis for a strong start with far-reaching roots, able to withstand variable conditions. 

Here we’ll discuss the best lawn soil mix to use when establishing a new lawn, and how to get it right.

Establishing a New Lawn

Choose the grass type wisely for your zone and sun.

Turf falls broadly into warm-season and cool-season types depending on growing season and climate.

Cool-season grasses tend to grow in zones 6 and colder, with Kentucky bluegrass, perennial ryegrass, and tall and fine fescues as common species. They withstand cold temperatures and thrive in spring and fall. Cool-season types may slow or become dormant in winter and summer heat.

Warm-season grasses grow in zones 7 and above and include Bermuda, St. Augustine, centipede, and zoysia. They grow vigorously in warm conditions and tolerate heat and humidity. Growth slows during extreme heat, and warm-season grasses enter winter dormancy when temperatures drop.

The first consideration for your site is grass type by growing zone, followed by additional factors like sun exposure and area use. Opt for a species or blended mix that suits the particular sun and shade conditions and foot traffic needs. Grasses also have variable maintenance requirements and drought tolerance.

When to Plant Grass

Avoid sowing too close to freezing conditions.

Whether sod or seed, new grass roots need time to develop before winter extremes. If you miss the window of late summer and early fall, opt for spring instead of risking planting too close to freezing conditions. Seeds won’t germinate and roots won’t develop if the soil temperatures are too cold.

In zones 6 and cooler, sow seeds or lay turf in mid-August through mid-October. To sprout, seeds need cool air and soil temperatures with regular moisture. The optimal soil temperature range is 50 to 60°F (10-16°C). Aim to sow seeds at least 45 days before the anticipated first frost date.

In zones 7 and warmer, the planting season is wrapping up. Plant warm-season turfgrass from March through September, avoiding hot and dry spells. Warm-season grasses rely on warm conditions to grow, and ideal soil temperatures are between 65 and 70°F (18-21°C).

Preparing the Site

A simple test shows exactly what lawn soil mix you need.

Site preparation for the new lawn involves clearing, topdressing, and smoothing the surface for good sod or seed-to-soil rooting contact. If you have a few weeks before the installation, a soil test is the best course of action. An at-home kit or one from your local University extension office makes the process easy.

Take soil samples from different areas of the site and combine them for a reading. With interpreted results, the soil test provides recommendations for specific amendments as they relate to turfgrass.

The results also include the amount of the amendment needed for your lawn soil mix. A soil test takes the guesswork out of garden amendments and topsoil mixes for a new lawn.

Remove Debris and Vegetation

Clear debris early to give roots space for growing.

While waiting for the soil test results, ready the site. Remove large debris like limbs, sticks, and rocks. Any surface impediments that block root development are spots where grass won’t grow.

Assess the surface to determine existing vegetation treatment and soil compaction. To remove large spans of existing grass or weedy areas, a sod cutter helps to remove the turf and roots. Sod cutters are available to rent at local hardware or equipment stores, and they save a lot of time and effort if working across a sizable area. They also eliminate the need for herbicides, which are another treatment option to kill off existing vegetation over a few weeks.

If you’re starting with bare earth, like a newly constructed home, you’re nearly ready to amend. Check soil compaction and drainage to determine if aerating or light tilling is necessary to break up existing topsoil or subsurface layers for root growth. Well-draining soils are essential for healthy blades.

Lawn Soil Mix

Rake or shovel small areas for smooth integration.

With the site cleared, it’s ready for topdressing with a lawn soil mix. If your soils are healthy with a pH suited to your grass type, there’s no need to amend. For most of us, they’ll benefit from a refresh after removing existing vegetation or with a new build. Heavy soils like clay and lean ones like sand improve with amendments.

Plan to topdress the site with a minimum of two inches, optimally four to six inches, of organic material like compost and/or screened topsoil (free of rocks and weeds). Organic matter improves drainage and aeration and provides nutrients.

After amending, incorporate two or so inches of the compost and topsoil mix with the top two to three inches of existing soil. Lightly turn small areas with a shovel or scuff with a hard rake. A rototiller kept nearer the surface works for large sites.

Loamy Topsoil

Well-draining soil retains moisture without drowning roots.

Loams are a blend of silt, sand, and clay and represent the optimal lawn soil mix for many plants. Loose and airy, they allow roots to penetrate to reach deeper moisture. They’re well-draining while moisture-retentive.

For the best topsoil mix for a new lawn, look for one that contains these materials. Topsoil should be crumbly (rather than sticky) and free of debris and chunky pieces.

Compost

Fine, humusy compost supports deep, strong root development.

A high-quality compost forms a rich foundation to improve heavy or lean soils. Add compost if the site’s total organic matter is less than 3% based on soil test results. Make sure to use wholly decomposed organic material so it doesn’t introduce weed seeds that defeat the purpose of our new lawn. 

Compost that’s not fully mature under the correct temperatures can harbor pathogens and even burn new grass. It should be debris-free, humusy, and fine-grained. Clumps should break apart easily by hand.

Spread an even layer of compost over the site’s surface, on its own or with new topsoil. Lightly incorporate the layers to improve the soil structure.

Sand

Heavy soil drains better with added coarse sand.

Coarse sand is a garden amendment to improve drainage in heavy soils like clay. It also helps to smooth and build small, patchy, bare spots for grass seed infill.

Clay soils require about a 60% sand base to improve drainage and aeration, which is a lot of sand. It can be costly for sizable turf areas. A blended topsoil works well with a smaller overall quantity.

Lime and Fertilizers

Adjust soil with lime or phosphorus as indicated.

A soil test is the way to determine soil pH and the need to balance acidity and alkalinity. The results also indicate fertilizer needs prior to seeding or sodding. Add lime to your lawn soil mix to balance acidic soils, and a phosphorus-rich fertilizer to boost root development.

Not all grass types or soils require additional lime or starter fertilizers, which is why a soil test is key. A standard application of limestone is 40 to 50 pounds per 1,000 square feet. Starter turf fertilizers are available for purchase and contain a higher phosphorus rate (the “P” in the N-P-K rate), like 5-10-10 and 10-20-20. Topdress with the correct amount of lime or fertilizer for the area’s square footage.

Smooth the Surface

Smooth the site for consistent seed or turf contact.

The final step in readying the site is raking the lawn soil mix to make it smooth and to distribute the amendments. Use a hard garden rake to remove clumps and clods and smooth high and low spots for a relatively even surface. A smooth area maximizes soil contact, improves drainage, allows even growth, and eases maintenance without hidden ruts or mounds.

Rake away large pieces. Particles should be marble-sized or smaller for the best foundation. With the site prepped, it’s time to scatter the grass seed or lay the turf.

Fall Watering

Even moisture keeps young blades strong through cool nights.

Whether tender seedings or fresh sod, the new lawn requires regular moisture to establish, and daily watering to start. Nurturing the new install for the first four to eight weeks, and until dormancy, is prime.

Grass keeps growing in the fall while temperatures are mild. It needs regular moisture until frost, whether from rain or supplemental irrigation. Irrigate the new grass until growth slows as temperatures drop and the ground freezes.