How deep does topsoil need to be for grass?
It can also also make the lawn more susceptible to drought stress or require more frequent watering. Grass roots grow between 4 and 6 inches long, so a layer of topsoil that's 6 inches deep provides enough room for the roots to grow.
Prepare the ground. Preparation for laying a lawn or sowing grass seed should begin a few weeks before you plan to sow seed or lay turf. Use a fork or spade to turn over the soil to a depth of 12 inches. Remove any weeds or stones.
- Fastest Cool-Season Grass. Perennial ryegrass seed germinates in seven to 10 days, compared to 10 to 14 days for tall fescue seed and 14 to 21 days for Kentucky bluegrass seed. Perennial ryegrass is one of the cool-season grasses to grow to obtain a thick lawn turf quickly.
- Seed warm weather grass seeds in early spring and into the summer. Wait until temperatures get above 65°F during the day and then seed. This will allow the warm weather grasses to get the benefit of warm temperatures that come with summer while giving them time to become established prior to cooler weather in the fall.
- Remove all debris and any wood, stones, or large roots. Use a spade and garden rake to scratch the soil 1 to 2 inches at the surface. Add seeding soil to the top of your existing soil and smooth with the rake. If you are not using seeding soil, add the starter fertilizer on top of the existing soil with a spreader.
You will need to measure the area's square footage to calculate cubic feet. To fill a garden bed, you need at least 8 inches of depth of topsoil. New lawns will do best if you spread a layer of 3-6 inches of topsoil before planting.
- The cost of topsoil depends a lot on location. In some areas of the US topsoil sells for about $12-$18 a cubic yard, with a delivery charge of $15-$60 depending on amount and distance (and delivery may be free with larger loads of 10 yards or more), for a total cost of $75-$150 for five yards, delivered.
- The absolute minimum quality soil depth for a care-free lawn is 10 cm (4 inches); however, for deeper root penetration and the benefits that brings, the accepted standard is 15 cm (6 inches).
- The depth of the bed can vary, but six inches of soil is a minimum. Plants need at least a 6–12-inch rooting zone, so 12 inches is ideal. Before you establish the bed, break up and loosen the soil underneath with a garden fork so that it's not compacted. Go about 6 to 8 inches deep.
Your topsoil is extremely important to your grass seeds but should be amended prior to any seed dispersal. In general, work about 4 inches of organic material, like compost, into your topsoil. By maintaining a friable and fertile topsoil habitat, your seeds have the best chance for vigorous growth and establishment.
- The germination time for grass seed ranges from 5 to 30 days depending on the variety. It can be even longer than this in cooler temperatures. This is how long it will take to actually see the grass growing. Until this point, the seed, or the soil and mulch in contact with the seed, must stay moist.
- When you spread grass seed into a thinning lawn, it is not necessary to rake the area. However, repairing bare soil patches with new grass seed does require raking. Similar to new lawns, your exposed topsoil needs to cover the grass seeds slightly for maximum growth.
- Sowing new grass seed over your existing lawn is known as overseeding. While it is often done to fill thinning or bare spots, you can also overseed your lawn to prevent browning during the winter by overseeding a warm-season lawn with a cool-season grass.
Updated: 26th October 2019