Basic steps for lawn renovation
Once the decision to renovate has been made, the procedure for carrying out the project follows some simple steps that, if done correctly, will result in a successful renovation.
First, test the soil and add any necessary nutrients.
If the lawn requires rejuvenation, rototilling the existing soil surface will be part of the renovation process.
- Begin by applying the required amounts of P and K to the soil surface just prior to rototilling.
- Incorporate the P and K to a depth of 4 to 6 inches. This ultimately places the nutrients in the rootzone of the mature grass plants. The nutrients can then be taken up by the plant and utilized to support healthy growth.
See Grass plant growth and its relationship to lawncare for more information on turfgrass biology.
If rototilling the existing lawn is not necessary, P and K additions can be applied after aerifying the lawn.
- After aerifying the lawn, apply the nutrients to the soil.
- Lightly drag the lawn surface. This will work the nutrients into the aerification holes and help break up the soil cores; this places the nutrients deeper in the rootzone where they can be accessed by the mature grass plants.
For more information on adding other soil amendments (e.g., topsoil, compost) see Proper soil preparation, Establishing a new lawn to achieve sustainability or contact the local county extension offices or the University of Minnesota Soil Testing Laboratory at 612-625-3101.
Weed control/removal can begin at about the same time the soil test is taken. Remove existing weeds from the area to be renovated; especially perennial broadleaf and grassy weeds. Leaving existing perennial weeds and grasses can invite future weed problems.
Examples of perennial broadleaf weeds include:
Examples of perennial weedy grasses include:
For more information on weed identification, growth habits and control measures, see Is this plant a weed?.
Selective vs. non-selective herbicides
- Selective Broadleaf herbicides labeled for use on lawns will control broadleaf weeds without harming existing lawn grasses. If the renovation project includes reseeding, reference the product's label for the correct amount of time to wait prior to seeding.
- Perennial grassy weeds are best controlled using a non-selective herbicide such as:
- glyphosate (trade name Round-up)
- glufosinate-ammonium (trade name Finale)
Reseeding before the prescribed amount of time has lapsed can result in significant injury to the new grass seedlings and make for a very poor, thin stand of turfgrass.
Note that non-selective herbicides will kill all vegetation (broadleaf weeds, grassy weeds and lawn grasses) that the product comes in contact with. However, killing all of the existing vegetation prior to seeding or sodding may be the most appropriate choice in a renovation project. Removal of existing vegetation creates a clean surface from which to start (i.e., reseed) with minimal future competition from those weeds.
As with the selective broadleaf herbicides, follow label directions on the non-selective products for the recommended waiting period before seeding or sodding. The waiting period allows the product to be absorbed and ultimately destroy the plant.
3. Mowing prior to overseeding
Before overseeding, mow the existing lawn very short to the point of scalping. This allows higher levels of sunlight to reach the soil. It also encourages faster germination and establishment of the new seedlings.
If the renovation is a thatch removal only project, then grass can be left slightly longer than when planning a thatch removal and overseeding project.
For example, if the normal height of cut is 2.5 inches, mowing it to 1.25 or 1.50 inches will be sufficient for a thatch removal only operation. This will remove excess debris from the lawn surface creating less interference with sowing seed and other renovation practices.
As illustrated below, thatch is the layer of brown fibrous material located just above the soil/mat layer but below where the turfgrass plants are green and visible.
Thatch is composed of both living and non-living material, most of which is an accumulation of non-living plant organic material associated with normal grass plant growth.
Thatch accumulates when excess organic material has settled and cannot be broken down. A thatch layer of 0.5 inches or less is acceptable as it gives a cushioning effect for human physical activity. It should be noted that grass clippings are not part of the thatch layer as they are readily decomposed.
Thatch removal methods:
- Hand raking: Thatch is a tough, interwoven organic material so it is very difficult to remove by hand raking. While vigorous hand raking may be sufficient in removing thatch in a limited area, hand raking is not practical for large areas or extreme thatch problems.
- Vertical mowing: Efficient removal of thatch generally requires the use of a powered machine known as a vertical mower (power rake or dethatcher). When vertical mowing is done properly, thatch will be brought up to and deposited on the lawn surface. In most instances, this thatch material should be raked off of the lawn surface so as not to interfere with any seeding work that is to be done. Thatch can be composted or used as mulch in other areas as it readily breaks down once in contact with soil. Vertical mowing is a common service provided by the lawn care industry and can be done for hire. Mowers are also available for rent.
- Sod removal: In large areas of thick thatch development (i.e., greater than 1.5 inches) the simplest means of removing excessive thatch may be to remove the entire lawn area back to the soil surface using a sod cutter. Sod removal is also a common service provided by the lawn care industry and can be done for hire. Cutters are also available for rent.
- Core aerification: This management practice is often performed in the spring when the turfgrass has started to green up, but the soil has dried out sufficiently to be firm underfoot and no longer soft and spongy.
Once the sod has been removed, either reseeding or resodding can begin immediately.
However, the optimal time of year to perform this operation is around Labor Day. This time of year allows the grass plants to recover from any injury during the favorable, less stressful growing conditions of late summer and fall. This time of year is also an excellent time to begin reseeding following the thatch removal process.
A vertical mower can also be used in thick thatch situations but will likely take more than one growing season to significantly reduce the thatch layer.
After thatch removal, it is necessary to prepare the soil surface for seeding.
- Begin with hand raking.
- Vigorous hand raking is suitable for small patches with little vegetation.
- Core aerification is the removal of cores of soil to improve soil air exchange, thus enhancing grass plant growth.
- Three to five passes over the lawn with a commercial core aerifier is suggested, especially if the soil is compacted
- Compacted or not, core aerification at the time of renovation is a beneficial practice.
- Vertical mowing can also be used as a soil preparation technique when sowing seed. The soil surface is lightly loosened by the use of a vertical mower. In addition, thatch levels can be reduced - providing an improved seed germination environment.
- Vertical mower tines should be set so they just nick the soil surface, penetrating no more than 0.25 to 0.5 inches.
- Usually a single pass with the vertical mower is sufficient.
- A vertical mower works well when preparing the soil surface beneath trees; use of a rototiller or core aerifier under trees will disrupt and injure roots near the surface.
Note in the photo on the left, there is just enough contact with the soil such that a shallow, loose layer of soil is created on the lawn surface. This layer of soil greatly improves the ability to incorporate the seed into the ground and ensures good seed-to-soil contact, rapid establishment of the young turfgrass seedlings and allows for a faster rejuvenation of the lawn.
Vertical mowers are also available with a seeder attached so that soil surface preparation and seed incorporation into the loosened surface soil can be accomplished simultaneously. In this case, seeding in two opposite directions (i.e., perpendicular to each other) will provide more uniform seeding. Be careful not to embed the seed too deeply into the soil as that can significantly slow down germination or perhaps prevent it altogether.
Slit-seeding [link to step 8 in this section] via a gas-powered slit seeder as a more advanced method of ensuring good seed-to-soil contact. It is usually best done by a professional but smaller, homeowner units may be available from your local rental shops as well.
There are several methods of spreading seed onto a prepared soil surface. Examples of hand seeding through gas-powered slit seeders are outlined below.
- Hand seeding:
- Divide seed lot in half to quarters and seed in two or four directions for seeding.
- For patches or small areas (less than 8 feet across), mix 1 part seed with 4 parts of a natural organic fertilizer like Milorganite®. This is termed "bulking-up" the seed and makes small amounts of seed easier to distribute uniformly.
- Do not use a corn gluten meal product for this purpose as it will damage or destroy the new grass seedlings.
- Rotary spreader: This is an acceptable method when the seed is bulked-up with natural organic fertilizer as described in hand seeding.
- Seed in two directions.
- Avoid this method during even light levels of wind as it will be very hard to distribute the seed uniformly.
- A better machine for seeding in light windy conditions is a drop spreader or a gas-powered slit seeder.
- Seeding should be delayed during wind conditions of greater than about 10 miles per hour. Proper seed distribution and incorporation into the soil is much more difficult in windy conditions.
- Drop spreader: This method is often used when seed is used alone or bulked-up as described in hand seeding.
- Seed in two directions or overlap 1/2 of previous swath.
- This is best done during calm or very light wind conditions for best results.
- Slit seeding: Equipment can be rented but requires skill to operate correctly; generally best done by a professional; go over site in two directions using half the seeding rate in each direction.
- Mulch: Fiber pellet mulches that contain a starter fertilizer and other germination enhancement materials may be used to support seedling development and increase moisture retention.
- These can be especially helpful if the ability to keep the area damp during the germination and early seedling growth stages will be somewhat inconsistent.
- Uniformity of early growing conditions, especially moisture, is very important to successful establishment.
- Mulches can be a significant aid to help ensure this consistency.
- Hydroseeding: Available from professional installers. For more information see Hydroseeding and Hydromulching and Establishing a New Lawn to Achieve Sustainability.
Scatter seed by hand Seeding rate too high Seeding rate about right
At seeding time:
- Apply additional phosphorus (P) and potassium (K) as determined by a soil test.
- In situations where the existing lawn is not killed-off prior to overseeding, avoid fertilizers with a high percentage of nitrogen (N) as it will stimulate vegetative growth of the existing turfgrass.
- In turn, this creates potentially significant competition for the newly germinating turfgrass seedlings and makes successful establishment more difficult.
- Even when overseeding thin areas of the lawn without doing any soil preparation (e.g., tilling or aerification), a lawn starter fertilizer that is higher in P (i.e., the middle number on the fertilizer bag) applied prior to seeding is beneficial for early grass plant growth.
- For best results lightly rake soil surface to incorporate fertilizer and improve seed-to-soil contact.
During early establishment:
- Fertilize with 1/2 pound of actual N per 1000 ft2 from a slow release N source after the first mowing.
- This will help ensure continued vigorous growth of the new grasses and aid in more quickly covering the soil surface.
- the more quickly grass cover can be established over the soil/lawn surface, the less chance there will be for weed encroachment to occur.
Proceed with the following to ensure proper irrigation:
- Once the seed is planted, ensure that the soil is kept evenly moist, although slight drying between watering is not detrimental and may even be beneficial.
- Thoroughly water soil initially then allow the surface to dry slightly before watering again; this may take a day or two depending on weather.
- At no time should the soil be allowed to completely dry out once the initial water has been applied.
- South-facing slopes and other parts of the lawn exposed to hot afternoon sun may dry out more rapidly and require additional watering on a more frequent basis.
- Moisture is also critical once seeds start to germinate. Water lightly and often enough to keep the soil surface just damp. The seedlings should not be allowed to dry out nor should the surface be constantly soggy.
- After the majority of seeds have germinated, water more heavily but less frequently to encourage deeper rooting.
- Be sure that all the different grasses contained in a mix have germinated before reducing moisture.
- Remember, Kentucky bluegrass can take 3 to 4 weeks to germinate.
- Establishment should take 6 to 12 weeks depending on the seed mixture used.
- A lawn seeded in late summer (mid-August to mid-September), should be usable the following spring.
Follow these steps to following irrigation
- Initially, maintain the shorter height of cut on the existing lawn to ensure that enough sunlight will continue to reach the new seedlings.
- Continue these shorter heights of cut for about 1 month or until the slowest germinating seeds are up and growing.
- As the new seedlings develop and attain the same height as the existing turfgrasses, the overall height of cut can be raised to the desired level.
The preferred time for lawn overseeding and renovation is from mid-August to early-September. The next best time is typically early spring just as the lawn is beginning to turn green and grow. Proceed to Lawn reseeding and overseeding
Disclaimer: Information given in this publication is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by University of Minnesota Extension is implied.