If your lawn is still more than 50 percent weeds after a few years, it might be time to consider a complete renovation. Planning is critical because during renovation your soil is unprotected and can easily be washed away into surface waters.
Late summer or early fall is usually the best time to establish or renovate cool-season grass lawns in most of New York. (August 15 to September 25, or as late as mid-October downstate and on Long Island.) Temperatures are moderating, weeds are less competitive, and moisture is usually adequate.
Follow these 12 steps carefully:
1. Control perennial vegetation.
This step will keep other species from competing with your new grass.
The most effective way to eliminate existing weeds and turf is with non-selective herbicides that contain the active ingredient glyphosate (Round-up
®, for example). Other non-selective herbicides include glufosinate (Finale
®) or the herbicidal soap formulation Scythe
®. Keep traffic off the grass until the herbicide dries on the leaves.
These herbicides are designed to kill any plant on contact but do not kill weed seeds. Once in contact with the soil theys are inactivated. This permits planting the new lawn just 5 to 7 days after spraying.
To ensure an effective kill, wait until the vegetation appears chlorotic (yellow). Then either till the vegetation into the soil, or run a slicer or dethatching tool over the killed sod.
2. Protect and test soil.
Minimize cultivation and compaction to maintain good soil structure. If the site needs grading, this might mean removing and temporarily storing the topsoil.
Before establishing the final grade with the topsoil, have it tested by a reputable soil testing lab. The information the lab provides will tell you how much fertilizer, organic matter, and other amendments are needed to establish a healthy new lawn. Allow two to three weeks for test results.
3. Establish a rough grade.
Take care of grade problems before you replant. Now is the time to eliminate low spots and take care of other drainage problems. Gently grade steep slopes to make mowing easier. Fracture compacted subsoil layers to help water move down through the soil profile.
4. Amend and grade topsoil.
Cover the subgrade with at least 4 inches of topsoil. Ideally, the interface between the subgrade and topsoil should be gradual, not abrupt. Till a few inches of topsoil into the subsoil, then add the remaining topsoil to the surface. If the topsoil is high in clay, add compost materials that are good soil conditioners and have relatively high amounts of nitrogen and phosphorus. These include:
- Biosolid composts such as Milorganite
Brewery by-product composts such as Allgro
Animal-manure and yard-trimming composts such as Erthrite
Paper-mill by-product composts such as Glatco-lite
Sandy soils can be amended by incorporating a small amount of clay or organic material to enhance water- and nutrient-holding capacity. Add high-phosphorus starter fertilizer with about 1 lb. N/1,000 square feet and/or pH modifiers such as lime or elemental sulfur based on information from your soil test.
5. Choose the right grass.
The species and variety you choose will depend on:
The quality of sod you expect.
How much work you want to do to maintain it.
How you plan to use it.
The characteristics of the site, including the amount of sun.
Resistance to insects and diseases.
See Choosing lawn grasses for more information.
Planting seed costs less than sodding. But use sod instead of seed when rapid turf cover is needed -- for example on slopes that need to be protected from erosion. Most cool-season sods are improved Kentucky bluegrass varieties because their spreading rhizomes intertwine to form a strong sod. Use high-phosphate starter fertilizer when laying sod, just as you would with reseeding.
Keep sod in shade so it doesn't dry out, and install it as soon as possible. Lay it in a staggered brick-like fashion, matching the edges closely.
6. Seed at the right rate.
The larger the seed, the higher the seeding rate. Studies show that there is no benefit from seeding more than the recommended rate. Excessive seeding rates create too much competition between the seedlings. Seeding at the correct rate or slightly lower encourages tillering - lateral spreading of the grass plants. (Sometimes if conditions are less than ideal, a higher seeding rate may be justified.)
Use a drop spreader or rotary "spin" seeder calibrated to deliver half of the recommended seeding rate. Then apply the seed in two different directions at right angles to each other. This assures more uniform coverage.
If you are reseeding a small patch, you can mix 1 part seed to 3 parts soil in a bucket and then spread the mix over the patch. This will help you spread the seed evenly. Ideally, you should end up with about 15 to 20 seeds per square inch.
See Choosing lawn grasses for more about seeding rates of different grass species.
7. Rake lightly.
Mix the seed and soil so that the seed is covered no more than 1/16 to 1/8 inch deep.
8. Firm the soil.
Light rolling assures good seed-to-soil contact needed for the seeds to take up water and germinate. (For small patches, just firm with your feet.) Do not overfill the roller as it may crush seed and cause compaction. A properly rolled seed bed can reduce establishment time by as much as two weeks.
Use weed-free straw or marsh hay to conserve moisture and help prevent erosion. (Avoid pasture hay as it is often loaded with weed seeds.) Other effective mulching materials include products made from wood fiber, excelsior, newsprint and other kinds of erosion-control blankets. Products made from a combination of pelletized newsprint, and water-absorbing gel such as PennMulch® are also effective.
Germinating seeds and young seedlings will quickly die if allowed to dry out. Keep seedbeds moist at all times until seeds emerge. Water only enough to moisten the surface. Do not overwater, causing runoff. Gradually reduce water after seedling emergence to encourage deeper rooting. Once grass covers about 60 percent of the ground, the surface should be allowed to dry.
About 2 to 3 weeks after emergence, apply about 1 lb. N/1,000 square feet. This will increase shoot density and the seedlings' ability to withstand diseases such as rust.
Once more than 60 percent of the grass reaches the recommended mowing height (at least 2 to 3 inches), start mowing. Mowing encourages lateral shoot development, increases stand density, and helps the turf out-compete weeds. Make sure your mower blade is sharp. Dull blades will tear young seedlings from the soil.
Be sure to study up on the best ways to mow, water, and fertilize to keep your new lawn healthy.