How to Plant Grass Seed on an Already Existing Lawn

Planting grass seed on an already existing lawn can breathe new life into tired, worn out grass or help fill in bare or thinning spots. With some preparation and proper seeding techniques, you can get a lush, green lawn. Here is a step-by-step guide on how to plant grass seed on an already existing lawn.

Materials Needed

  • Grass seed – Use a mix suitable for your climate and sun exposure. Cool-season grasses like bluegrass, ryegrass and fescue are recommended for northern regions while warm season varieties like Bermuda and zoysia work best in southern areas.
  • Fertilizer – A starter fertilizer high in phosphorus will help the new grass establish an extensive root system. Choose an organic or synthetic fertilizer.
  • Topsoil – Needed to fill in low spots and uneven areas. Opt for high-quality screened topsoil without excessive clay.
  • Compost – Enriches soil with organic matter to help retain moisture and nutrients. Well-aged compost with fine texture works best.
  • Straw – Used to cover newly seeded areas to retain moisture and regulate soil temperature. Stay away from hay which has weed seeds.
  • Garden rake – For loosening soil, removing debris, leveling the lawn and working in amendments. Choose a steel rake with short, stiff tines.
  • Push broom – Help work seed into the soil and smooth the planting area prior to seeding. Look for a broom with synthetic bristles.
  • Wheelbarrow or tractor – Makes transporting soil, compost and other materials around the yard much easier. A contractor-grade wheelbarrow or riding lawn tractor is ideal.
  • Spreader – For evenly distributing seed and fertilizer over the lawn. Get a push spreader for small yards or a pull-behind broadcast spreader for larger lawns.
  • Garden hose – Necessary for watering newly planted seed several times per day. Look for a flexible, kink-resistant hose at least 50 ft. long.
  • Sprinkler – Use oscillating or pulsating sprinklers that provide full, even water coverage without excessive misting.

Timing Considerations

Spring – The optimal time to seed cool season northern grasses like Kentucky bluegrass or tall fescue. Plant as early in spring as possible once soils thaw.

Fall – The best season to plant cool season grasses in northern regions. Seed from late summer through early fall for grass that will establish before winter dormancy.

Summer – Avoid seeding during hot, dry summer months. New grass will struggle to germinate and needs frequent watering to survive. Focus on fall seeding instead.

Warm Season Grasses – Best seeded in spring after the last expected frost. This gives grass such as Bermuda, zoysia or buffalo grass ample time to develop before winter.

Weather – Seed grass when a span of mild, consistent weather is forecasted. Avoid seeding right before heavy rains or periods of high heat. Monitor upcoming weather patterns.

Lawn Assessment

  • Inspect the lawn to determine problem areas, thatch buildup, low spots, weeds or diseased patches. Identify areas in need of seeding.
  • Conduct a soil test through your local extension office to analyze pH and nutrient levels. Make any recommended amendments.
  • Check the lawn mower blade and ensure it is sharp. Sharpen or replace the blade if dull. Set the height for the tallest recommended setting.
  • Spray any broadleaf or grassy weeds at least one week before seeding. Weeds will compete with new grass so eliminate them early.
  • Dethatch or aerate if grass is excessively thick or soil is heavily compacted. Dense thatch makes it harder for seeds to contact soil.
  • Fill any holes, low areas or erosion zones with fresh topsoil. Water well and let it settle before seeding into these sections.

Seeding Preparation

Mow Low – About 1-2 days before seeding, mow the lawn shorter than usual at the lowest mower setting. This allows seed to reach the soil surface easier. Remove and bag all clippings.

Eliminate Debris – Use a steel rake to remove any sticks, stones, leaves or other debris that could prevent seed contact with soil. Discard debris.

Loosen Soil Surface – Use a stiff push broom to gently scuff up the soil surface layer. This creates small grooves for seed to lodge in. Scuff in two directions.

Apply Starter Fertilizer – Spread starter fertilizer over the lawn at the recommended rate using a broadcast spreader. Water lightly to activate the fertilizer.

Spread Compost – For areas that feel compacted or lack organic matter, apply a thin 1/4″ layer of compost. Mist lightly to keep it from blowing away.

Final Debris Removal – Do a final pass with a rake over the entire lawn to remove any last bits of debris brought up from soil prepping.

Seeding Methods

Over-seeding Existing Grass

This method involves scattering new grass seed over an established lawn. It improves the lawn’s appearance and fills in thin or bare patches.

When to use: For lawns with minor thinning or small bare areas less than 10% of the total size. Not for lawns in need of complete renovation.


  • Mow the lawn short, bag clippings, dethatch if needed.
  • Use a spreader to apply seed at the recommended rate. Opt for a mix of similar grass types already in the lawn.
  • Spread very thinly to avoid smothering existing grass. Go lightly over thinning areas.
  • Consider mixing in a small amount of annual ryegrass at 2-5 lbs per 1000 sq. ft. This provides quick cover as the new perennial grass establishes.
  • Gently rake the entire lawn to lightly work seed into the soil surface without disturbing existing grass.
  • Use a push broom to further press seed into the soil so it makes good contact.
  • Mist seeded areas with water to avoid seed washout. Don’t soak at this point.
  • Cover with very light 1/4″ layer of straw held down by a biodegradable erosion netting.
  • Water lightly 3-4 times daily until new grass emerges. Reduce frequency as it establishes.

Seeding Bare Spots

For repairing bare, dead grass patches or areas where grass failed to establish. Focus efforts only on bare sections.

When to use: For bare, dead or thinning spots taking up less than 15% of the total lawn size. Not for completely bare lawns.


  • Dig out dead grass and debris from bare areas. Break up compacted soil with a fork or shovel.
  • Fill any holes or dips with fresh topsoil. Water and let it settle before seeding.
  • Loosen top 1/4″ of soil in bare spots with a rake. Smooth and level the seed bed.
  • Select a grass seed variety that matches existing lawn grass type. Use a concentrated seed rate.
  • Sprinkle seed only over bare areas. Apply sparingly and cover lightly with 1/8″ layer of screened compost.
  • Gently rake seeded spots to settle seed into topsoil. Mist with water.
  • Cover bare spots with light straw layer no more than 1/2″ deep to allow sunlight to penetrate.
  • Water gently 2-3 times daily until seed germinates and new grass arrives. Slowly reduce watering frequency.

Seeding New Lawn Areas

This technique prepares and sows an entire section for brand new grass growth, such as a new lawn.

When to use: For establishing grass in a completely new, bare lawn area that has no existing grass.


  • Remove any weeds, rocks, roots and construction debris. Dig out vegetation and grade smooth.
  • Spread 2-3″ of fresh topsoil over the area if underlying soil is poor or heavily compacted.
  • Level and smooth the entire area. Roll with lawn roller if needed to firm up loose soil.
  • Use a rake to create shallow grooves in two directions which gives seed vales to settle into.
  • Select high-quality grass seed suited for sun/shade and climate conditions. Use proper seed rates.
  • Spread starter fertilizer evenly according to label rates before seeding. Water in well.
  • Distribute seed evenly over the bare area using a broadcast spreader. Go over entire area twice in opposite directions.
  • Cover broadcasted seed by raking entire area to settle seed gently down into soil grooves.
  • Use a lawn roller again to ensure seed has good contact with soil. Mist gently with water.
  • Protect newly seeded area with a straw erosion control blanket pinned down or light 1/2″ layer of loose straw.
  • Water lightly 3-4 times daily until seedlings emerge. Gradually reduce to deeper, less frequent watering for stronger roots.

Post-Seeding Lawn Care

  • Expect new grass seedlings to emerge within 2-3 weeks of seeding. It can take 4-6 weeks for full establishment.
  • Water daily in light increments. New grass has shallow roots and dries out quickly. Avoid runoff.
  • Once grass reaches 3″ tall, mow lightly at a high setting. Bag clippings the first 2-3 mowings until thicker.
  • Apply more starter fertilizer when grass reaches about 4-6″ for continued root and shoot growth. Follow rates.
  • Overseed any sparse areas again after 4-6 weeks. Fall overseeding often boosts spring bare spots.
  • Avoid heavy traffic on newly seeded areas until the lawn has fully established after about two months.
  • Control disease and insect issues which can damage young tender grass. Scout for problems.
  • Weed preventer applications after 30-60 days are okay for mature enough grass. Read product labels first.
  • Adjust watering to typical lawn needs by mid season. Mature grass requires about 1-1.5″ of water per week.

Troubleshooting Problems

Seed not germinating – Ensure adequate consistent moisture. Reseed areas after aerating to improve soil contact. Cover with light straw layer.

Patchy or spotty growth – Overseed thin areas again using a starter fertilizer to thicken up growth. Ensure sprinklers have good coverage.

Seed washed away – Heavy rains can cause runoff on slopes or bare soil. Cover seeded areas with erosion control blankets to hold seed in place.

Grass dying out – New grass needs about 1-1.5″ of water daily in light increments for the first month. Ensure regular irrigation.

Weeds invading – New grass is vulnerable to weed competition. Hand pull weeds around young grass plants. Overseed any bare spots.

Pests present – New grass can attract chinch bugs, grubs, armyworms or other pests. Apply appropriate insecticides if infestation is severe.

Diseases developing – Fungus issues like dollar spot thrive on tender new grass. Use fungicides and improve air circulation around plants.

Final Tips

  • When overseeding, apply 50% of normal seed rate. When establishing new lawn, go with 100% full seed rate.
  • Water new grass seed for roughly 10 minutes, 3 to 4 times per day until shoots emerge. Soak soil 6-10″ down.
  • For best results, plan seeding when daytime temperatures will remain under 85°F for 4-6 weeks after planting.
  • Consider blending slow and fast growing grass types. Fast varieties deliver quick cover while slow grasses provide long term permanence.

-TestBase soil nutrient levels and pH first. Adjust as needed so new grass has proper fertility for strong establishment.

  • Do not allow newly seeded lawn areas to dry out. Maintain consistent moisture levels for the first two months.
  • Be very patient. It can take at least 2-3 months before newly seeded lawns start looking fully filled in and established.

Frequently Asked Questions

When is the best time to plant grass seed?

For cool season grasses, the optimal seasons are early spring through early summer and early fall through late fall. Avoid the hottest summer months. Warm season grasses thrive when seeded in late spring after the soil warms up.

How long does it take for new grass seed to grow?

Depending on weather and moisture conditions, the first shoots and leaves can emerge within 10-14 days after planting. It takes 4-6 weeks for newly seeded grass to become fully established with a developed root system.

What is the best grass seed for my lawn?

Choose grass varieties suitable for your climate and sun conditions. Popular cool season grasses include bluegrass, fescue and ryegrass. Warm season grasses like Bermuda and zoysia work well in hot, southern regions. Your local extension service can provide recommendations.

How do I prepare soil for planting grass seed?

Proper soil preparation is key. Remove debris, loosen up the top 1-2″ of soil, level low spots, apply starter fertilizer and a thin layer of compost before seeding into a friable, enriched seed bed.

How much grass seed do I need per square foot?

When overseeding thin lawns, apply approximately 5-8 lbs of grass seed per 1000 square feet. For new lawns, double that rate to 10-15 lbs per 1000 square feet for full, even coverage. Follow package directions.

When should I fertilize new grass seed?

Apply starter fertilizer to newly seeded areas once grass plants are around 3-4 inches tall. This gives the developing root system a boost of phosphorus for strong establishment.

How often and how long do I water newly seeded grass?

Water new grass seed lightly 3-5 times per day for roughly 10 minutes to keep the top 6 inches of soil consistently moist. Reduce frequency as grass matures. Proper watering is critical for the first 8 weeks.

What is the best way to water grass seed?

Use a sprinkler system or oscillating sprinkler to provide uniform coverage. By hand, use a nozzle with a very fine mist setting to avoid washing away seeds or soil. Avoid heavy flooding.

When can I mow newly seeded grass?

Once the new grass reaches about 3 inches tall after 3-5 weeks, you can do the first mowing. Set the mower high (3.5-4″), bag clippings and use a walk-behind mower to avoid compacting soil.


When replanting grass into an existing lawn, proper timing, site preparation and seeding techniques are vital for success. Always select high quality seed well-suited for the lawn’s sun exposure, climate and soil. Prepare the seed bed by loosening soil, removing debris and evening out bumps and dips. Sow at the recommended seed rate, water lightly several times daily, and allow ample time for germination and establishment. With patience and diligent care, newly planted grass seed will transform into a lush, thriving lawn.

How to Plant Grass Seed on an Already Existing Lawn

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Overseeding or replanting grass seed into an existing lawn is a great way to thicken up thin areas, fill in bare spots, and boost the overall health and appearance of the turf. The process of planting new grass into established turf takes some care, patience and proper technique to ensure success. This comprehensive guide covers everything you need to know, from choosing the right grass seed and prepping the site, to seeding methods, post-care, and troubleshooting issues. With the right steps, planting grass seed can breathe new life into tired lawns.

Choosing the Right Grass Seed Variety

  • Match seed to existing grass – Look for same species, or blend of improved varieties. Avoid drastic grass type changes.
  • Buy quality seed – Certified, high purity and germination ratings. Avoid generic seed. Purchase from reputable supplier.
  • Select by climate – Cool-season grasses for northern regions, warm-season types for southern zones. Confirm regional suitability.
  • Factor in sunlight – Some grasses perform better in shade vs. sun. Choose seed suited for conditions.
  • Consider grass characteristics – Fine texture? Wear tolerance? Growth rate? Color? Choose seed that meets lawn’s needs.
  • Have a purpose – What do you want to achieve? Thicker growth? Fix bare spots? Improve lawn’s appearance? Buy seed tailored for goals.
  • Purchase in fall – Best availability and freshness. Seed before winter dormancy.
  • Check expiration dates – Use within recommended shelf life for optimal germination.

Lawn Assessment Before Planting

  • Analyze lawn’s current condition and needs
  • Identify bare, thin, diseased or compacted areas in the existing turf
  • Decide which sections need renovating with new seed
  • Conduct soil test, check pH and nutrient levels
  • Determine average sunlight, shade and traffic patterns
  • Remove debris, rake up leaves, clear out problem weeds beforehand
  • Make any necessary soil amendments per soil test
  • Mow, dethatch and eliminate bumps or low spots
  • Repair irrigation coverage if spotty or inadequate
  • Plan timing wisely according to grass seed variety chosen

Optimal Time To Plant Grass Seed

  • Spring – Early portion before summer heat arrives.
  • Fall – From late summer until first frost. Best for cool-season grasses.
  • Avoid summer – Heat, drought stress and diseases can damage new grass.
  • Know first frost dates – Plant 6-8 weeks before so grass establishes.
  • Temperature requirements – Most thrive and germinate at 60-75°F.
  • Seed warm season in spring – Needs heat, avoids winter kill.
  • Watch weather patterns – Prolonged rains or heat waves can ruin new