Step 1: Prepare Your Lawn
MOW YOUR LAWN. A lower cutting height reduces competition from existing grass and helps seeds reach the soil. Mow your lawn to about 1-1/2 inches and bag the clippings.
REMOVE THATCH AND DEBRIS. Grass clippings collect at the base of the plant and form a matted layer called thatch. Thatch over ½ inches thick can prevent seeds from reaching the soil. If the thatch is too thick, water and nutrients will also be prevented from reaching the soil. Break up and remove thatch with a rake before seeding. This allows seeds to reach the soil.
Step 2: Aerate the Soil
CORE AERATION fights compaction and allows water, fertilizer, and oxygen to enter the root zone. Use a core aerator (rented from a garden supply or hardware store) to remove small plugs of soil, improving soil compaction and allowing water, nutrients, and oxygen to reach the root zone. Aerate the lawn in one direction, then again at a 90-degree angle.
At the end of the process, your yard should be littered with 2-3-inch plugs. Leave the plugs (don't rake them up) to boost your yard's nutrients as they decompose.
AVOID OVER-AERATION. Aerating too frequently can stress your lawn. Aim to aerate once a year, ideally in the fall.
Step 3: Choose the Right Seed
Choose a blend suitable for your region and lawn conditions. Is it shady or sunny? Extra wet? There is a grass seed or seed blend for every situation. Cool-season grasses like Kentucky Bluegrass and Perennial Ryegrass often work well in northern climates.
Consult the U of M Extension or your local garden center to determine the right variety and quantity for your lawn.
CHECK THE SEED LABEL. Ensure the seed is weed-free and has a high germination rate. Avoid using old seed, as its viability decreases over time.
Step 4: Seed Your Lawn
BEFORE SEEDING, cover bare spots with good black dirt for best results. You can spread your seeds by broadcasting with your hand (no tools required, but not the most consistent) or using a hand-held seed spreader or push spreader for even distribution.
APPLY THE SEED evenly across your lawn, focusing on bare or thin areas. Follow the recommended seeding rate on the seed package.
COVER THE SEED. Lightly rake the soil to cover the seeds. Consider applying a thin layer of topsoil or compost in bare spots to help retain moisture.
Step 5: Water Consistently
WATER LIGHTLY AND FREQUENTLY (2-3 times a day) for the first 10-14 days to keep the soil moist but not waterlogged.
Ideally, the top 2 inches of the soil will remain moist. This encourages deeper root growth, making your mature lawn resistant to heat and drought. Sandy soil dries out faster, and clay retains more water. Not sure what type of soil you have? Have your soil tested at the U of M, or perform this simple mason jar test yourself.
Once seeds germinate, reduce watering frequency but increase the depth to encourage deep root growth.
Step 6: Post-Overseeding Care
LIMIT FOOT TRAFFIC. Keep off the newly seeded lawn to avoid compacting the soil and disturbing the seeds.
WAIT TO MOW until the new grass is at least 3 inches tall. Cut to a height of 3-3.5 inches, and never remove more than one-third of the grass blade in a single mowing session.
FERTILIZE WHEN THE GRASS IS ESTABLISHED. To promote healthy growth, apply a balanced fertilizer once the grass reaches about 3 inches.
TEST YOUR SOIL to determine what fertilizer is right for your lawn. You can use a kit from a garden center or send a sample to the U of M soil lab.
Test kits from garden centers and big box stores may not have accurate results or give you any recommendations on what actions to take. (Here's what the U of M says about fertilizer.) Soil testing at the U of M takes about two weeks. They will not only tell you what kind of soil you have but also recommend what amendments to add to it, if necessary.
Common Overseeding Mistakes to Avoid
Skipping Soil Preparation > Seeds may not germinate or establish well without proper preparation.
Overwatering > Excess water can lead to seed rot and poor germination.
Using the Wrong Seed > To ensure successful growth, select a seed variety that suits your climate and lawn conditions.