Time to Renovate your Lawn?
Tips for Overseeding and Repair of Poor Lawns:
Renovation involves planting grass seed into an existing lawn, often adding new varieties to repair damage or increase tolerance to drought or shade. The first step in renovating a lawn is to correct the primary cause of lawn deterioration. Drought, compact soil, poor drainage, root competition, excessive shade, inadequate fertility, thatch, improper mowing, poorly adapted grass species, weeds, insects, diseases, or others may contribute to poor lawns.
Renovation can be as simple as over-seeding a thin lawn area
or include power raking and core aeration if thatch buildup is
greater than ½”, or, if the soil is compacted. A total renovation
would involve killing the undesirable grasses with a nonselective
herbicide and may require more than one spray application.
Renovation alone will not be sufficient if problems are too severe
from excessively compacted soils or greater than 50% weed or
bare soil. Starting a new lawn may be the best option where removal
of the existing turf, tilling, adding compost & topsoil, and
changing the soil grade are needed.
Should I Renovate My Lawn?
Early fall is the best time of year for lawn renovation because growing conditions are favorable and weed competition is much lower than in spring. In western Washington, the best time for seeding is between September and mid-October. The next best time for seeding is late March to mid-May as long as the soils are not too wet to work
1 - Control Undesirable Vegetation
• If moss is present, use an iron-based moss-killer to eradicate the moss. Wait three weeks after using a moss-killer before reseeding. Remove dead moss by hand (using a thatching rake)
or cultivator may help) or use a moss killer when the moss is
moist and green. Apply moss killer at least 3 weeks prior to
• Weeds can be removed manually, killed using a non-selective
herbicide that contains Glyphosate, or by using soil
solarization methods. Avoid using weed killers that persist in
the soil, such as soil sterilants. (Read the instructions
to determine the dilution rate and the recommended time to wait
before reseeding when using herbicides). For best results,
weeds should be actively growing and have plenty of leaf surface
for the herbicide to cover.
• Lawns having large patches of coarse weedy grasses such as velvet grass, orchard grass or bentgrass can be best renovated if all vegetation is killed with Roundup®. It will probably take more than one application to kill creeping perennial grasses which have deep rhizome roots.
• Grass and weeds must be actively growing in order to be killed. If this is not the case, apply a high-nitrogen fertilizer and water frequently for two weeks prior to using an herbicide. This will revive the grass and weeds. If the whole lawn is weeds, spray everything. If only a few patches exist spray only those weeds.
2 - Debris Removal
• Wait the recommended time on the herbicide label for the weed killer to reach the roots before removing weeds.
• Mow the area closely (approximately ¾”) setting your lawn mower on its lowest cutting height and remove all clippings, leaves and other debris by sweeping or raking.
• When thatch exceeds ½” it is best removed by vigorous hand raking, or the use of a power rake. Power rake the lawn as many times as necessary in different directions to remove accumulated thatch. (When dethatching your lawn, be sure to remove all plant debris so as to expose the existing soil. The tines should be set to nick the soil surface to a depth of 1/8 – ½ inch. Where thatch is excessive, removal with a sod cutter is recommended.)
Step 3 - Soil Moisture Replenishment
• Prior to seeding, a thorough soaking (to a depth of 6 – 8 inches) to replenish soil moisture will make soil preparation easier. It will also help ensure that young grass seedlings have sufficient water. This is very important in the fall after a dry summer season. The area will need to be thatched if dead moss or thatch is heavy enough to prevent the seed from dropping to soil surface.
For small jobs, hand thatching rakes work well or rental yards carry motorized thatchers for large jobs. Be sure to
remove loose thatch. The soil surface should be firm and lightly roughed.
Step 4 - Prepare Soil Surface (Aerating & Leveling)
• To alleviate compacted soils use a hand held coring aerator, or for larger jobs, a mechanical aerating machine which
removes plugs of soil for the lawn area. Aerate the lawn completely, going over it 3 – 5 times in different directions
when pulling plugs. Soil cores can be allowed to partially dry and then be broken up using a rake or power rake before
seeding. Aeration is helpful in creating better drainage, and makes it easier for nutrients and oxygen to reach the
roots. Filling the aeration holes with coarse sand will help maintain these benefits for a longer period of time.
• Fill in any holes and eliminate low spots and take care of any other drainage
• For low spots on the lawns bed, use a quality top soil. First, scratch the surface of the existing soil
to better blend the existing and new soils together. Add the top soil to the same level as the existing soil
and water to settle. After the top soil has settled add more top soil and water again. (This may have to be
done several times until the soil is even with the existing soil and is no longer settling). One reason why your turf
may be thin and need overseeding is because the soils are heavy, not allowing good drainage and blocking availability
of oxygen to the grass plant roots. The result is a weak stand of grass. The process of core aeration opens up the
soil allowing better drainage, oxygen availability and a healthier root system. Topdressing or filling the aeration
holes with screened compost or a course sand will help to maintain the benefits of aeration.
5 - Soil Test for pH & Fertility
• Test your soil for pH and fertility. Apply organic nitrogen fertilizer, Phosphate and Potassium as determined by soil test results. Apply an organic fertilizer such as “Dr. Earth Super Natural Lawn Food” to the area, (follow the recommended rates on the package.) Using a level-headed rake, work the fertilizer in to the top 1/4” of the soil.
• Apply pH adjusting products like lime to raise soil pH if needed. Lime should be applied in accordance with a soil test. If the lime requirement exceeds 100 lbs per 1,000 sq. ft., apply 100 lbs. now and the remainder the following spring or fall.
Step 6 - Grass Seeding
• Select a turf grass variety that is well suited to the Maritime Northwest. Turf-type perennial ryegrasses, fine leaved fescues are well adapted to western Washington. Kentucky Bluegrasses are usually short lived in the Puget Sound and Bentgrass requires far more maintenance than the average gardener will wish to provide.
• Seed at the right rate. The larger the seed, the higher the seeding rate. Excessive seeding creates too much competition between seedlings. Distribute the seed uniformly over the area to be planted. For smaller jobs a hand held spreader will suffice, for larger ones use a drop spreader.
• Apply one half of seed in two applications in different directions at a 90° angles to each other, this assures uniform coverage.
• Lightly rake in the seed so that the seed is covered no more than 1/16” or so with about 10% of the seed showing on the surface.
• A light application of screened compost (no more than ¼”) may be spread on top to help retain moisture and hide seeds from the birds.
7 - Germination and Watering
• The seeded area should be kept moist until the seed has germinated
and the seedling plants have become well established. New seeds
and seedlings will quickly die if allowed to dry out. Many
light irrigations are better than heavier waterings that can
tend to either drown the seed or float it away on a sloped area.
• During hot days multiple waterings may be necessary.
• Germination is dependent on soil temperature (above 50°F), sunlight and seed variety.
• You should see some seedlings germinating within two weeks depending on seed variety.
• Once seedlings have emerged, gradually increase the watering duration. Watering frequency may be decreased AFTER the lawn has become established.
• Traffic on a newly renovated lawn should be avoided for the first several weeks after seedlings emerge.
8- Let it Grow, Then Mow
• Mowing should first take place when 60% of the grass reaches the height of 3 – 4 inches tall. Mow to a height of 2 ½ inches tall with a sharp mower.
Always keep your lawn between 2” and 3” tall. (This helps keep weeds in check by blocking the sunlight from the soil surface. It also helps retain moisture and improves the overall health of the grass).
• Watering: After the lawn is established, water your lawn deeply during all dry periods. Apply 1” to 1½” of water once a week. Do not count on the light rains we get during late spring and early summer.
• More Tips for a Healthy Lawn
• A regular fertilizing and watering program will help provide a lush, green lawn year round.
• Applying dolomite lime every six months (at a rate of 25 lbs per 1000 square feet) is extremely helpful for maintaining neutral soil conditions which help to reduce moss in shaded or moist lawn areas.
• Yearly core aerating will help keep the lawn from becoming too compacted.
• Thatch decreases the vigor of turf grasses by restricting the movement of water, and nutrients into the soil. Thatch is the buildup of dead roots, rhizomes and stems at the soil surface and accumulates over a period of years which must be periodically removed by mechanical means. Do not allow the thatch to become more then ½” thick. When it does, use a thatching rake or power rake to remove as much as thatch possible.
• A good lawn should essentially last a lifetime if properly maintained as needed. Proper fertilization, mowing, watering, dethatching and over-seeding are needed on a regular basis.