Landscaper Pro Advice: Overseeding and Repairing Bare Areas

At some point in the year it will probably be necessary to overseed your lawn, either to repair bare/thin areas or simply to maintain a favourable sward composition within an ornamental lawn.  Depending on the reason the approach will be different.

How to repair bare/thin areas of lawn

Bare patches and/or thin areas of grass may appear in a lawn due to grass death which can be brought about for a variety of reasons.  General wear and tear by foot traffic and machinery can result in a thinning of the grass if concentrated in specific areas.  Otherwise, grass death can occur as a consequence of damage caused by pests and diseases and/or conditions such as drought stress and dry patch.

If left thin and bare these areas will become colonised by weed grasses, mosses and broadleaved weeds.  As well as impacting on the aesthetic quality of the lawn the presence of such weeds will increase the likelihood of further weed infestations and reduce the overall wear tolerance of the area.  It is therefore best practice to repair such damaged areas as soon as possible after they appear or at least as soon as conditions are favourable for the grass seed being sown.

Using seed to carry out repairs will be significantly cheaper compared with buying new turf / sod but will take longer to establish.  Turf / sod can be used successfully, especially if a section can be cut from the existing site to provide a good match of soil and sward composition.  It is however, very vulnerable to hot and dry conditions and access to suitable irrigation will be required depending on the timing of the work.

Top tips for successful repairs

• Ideally repair work should be carried out when soil temperatures and moisture levels are adequate for good seed germination and establishment. Access to suitable irrigation will increase the window of opportunities available.

• Remove any remaining dead plant material using a rake or similar implement taking care to minimise damage to remaining grass plants. For larger areas a scarifier could be used if necessary but ensuring that the treatment is kept light if growth is slow.

• The surface should then be opened up to provide a seedbed for the seed. If the area is compacted use a hand fork to fracture and fissure the soil to depth keeping the tines at close centres.  Alternatively, or for large areas, solid tine the surface using a punch action machine aiming to work the top 100 mm of the profile.  A tilth can then be produced by alternate raking and heeling.

• Apply a sandy loam topsoil or sandy rootzone to correct surface levels. Rake to incorporate into the top of the profile and ‘key-in’ with the underlying soil.

• Apply a slow release seedbed fertiliser with a high phosphorus content such as Landscaper Pro New Grass (20:20:8) at the recommended application rate and incorporate into the upper profile using a rake or similar implement.

• Sow seed either by hand or using a dedicated seeder. The sowing rate will vary depending on the choice of seed.  When repairing bare areas sow at the recommended seeding rate but reduce to half rate for thin areas.  Rake into the top of the soil – do not leave sitting on the surface where is can be blown away or eaten by wildlife.

• Given the vulnerability of seedlings to drought, ensure that adequate water is supplied, especially if conditions are hot and dry.

• Protect seeded areas from wildlife and foot traffic with netting/fencing.

• If conditions are cool, for example in early spring, consider using germination sheets to increase germination rate and speed up establishment.

• If turf / sod is used to repair bare areas ensure that the underlying ground is fully prepared and firmed in preparation. Work from planks of wood aiming to lay the turves level with the surrounding ground – do not be tempted to leave the turves proud in anticipation of future sinkage.  If the area does drop then surface levels can be corrected using top dressing, if not, the new turf will be scalped when mown.  Follow turfing with a light surface dressing to help the turves knit together.  Ensure adequate water is provided to prevent the turves from drying out and shrinking.

Why should I overseed a lawn?

The main aim of overseeding a lawn is to maintain a dense sward dominated by favourable grass species as well as introducing a more diverse range of cultivars to give a good level of disease resistance and year-round presentation.

Top tips for successful overseeding

• Timing is important depending on the seed mix to be used. Fine browntop bent seed needs good soil temperatures of 10⁰C and above for successful germination and establishment.  Many modern perennial ryegrass cultivars on the other hand can be successfully germinated within soils of just 4⁰C.  Refer to the manufacturer’s label recommendations.

• Lightly scarify or rake the surface to open up the existing sward and remove organic matter at the turf base.

• For small areas, solid tine or hand fork the surface prior to broadcasting seed by hand. Sow at half rate and split the quantity into two to achieve a more uniform spread.  Larger areas should ideally be sown using a dedicated seeding unit which will place the seed at the correct depth within the profile.

• Subsequently top dress with sand or a sandy rootzone.

• A slow release fertiliser with a high phosphate content such as Landscaper Pro New Grass (20:20:8) should be applied 5-7 days after sowing.

• Ensure that the area has adequate moisture to support successful germination and establishment.