Growing Together: How to repair a thin lawn
Did you know that lawns make our world a healthier place? Every section of lawn 5 feet wide by 5 feet long produces enough oxygen every day during the growing season to support one adult’s oxygen intake, according to the University of Minnesota.
Besides oxygen production, lawns reduce atmospheric carbon dioxide, prevent wind and water erosion, provide cooling to the surroundings, reduce noise and help break down organic chemicals. Well-kept lawns make neighborhoods inviting while encouraging interaction between residents. Lawns play a silent and often unrecognized part in strengthening connections in communities.
Lawns aren’t the only way to make a home yard healthy and attractive. Many homeowners are downsizing the amount of turf in their yard in favor of other planting options. But for homeowners who enjoy a grassy lawn, keeping it healthy is the goal.
Sometimes lawns don’t grow as full and uniform as we’d like. Common causes are low soil fertility, disease, pet urine and heavy clay soil that’s become compacted. As trees grow, increased shade can thin sun-loving grass types while tree roots compete for moisture and nutrients.
We might even be responsible for a lawn’s decline ourselves by mowing too short all summer and by giving frequent shallow sprinklings instead of deep waterings spaced appropriately to support deep prolific roots.
When a lawn isn’t thick and uniform, the problem is often random bare spots or a thin, lackluster turf across the whole lawn. We can repair each with separate approaches.
Random bare patches can be reseeded in early May, as soil warms to temperatures required for seed germination. If spots were caused by pet urine, first flood the spots with water to dilute and leach adverse compounds. Rake bare areas to reduce excess debris and dead grass to provide better contact between seed and soil. Bare soil is not required, and some stubble helps keep the spots moist for better germination.
If the bare lawn patches have deteriorated to bare soil, a light mulch of dried grass, straw or commercial mulch products will help conserve moisture. Keep bare areas dark-moist until grass seedlings are visible.
If the entire lawn is thin and patchy, a general overseeding might be the best remedy. Begin by mowing the existing lawn as short as possible so new grass seedlings will get enough sunshine. To reduce thatch so seed can contact soil, power raking (dethatching), core aeration or brisk hand-raking will help.
When selecting grass seed for lawn repair, bargain mixes are usually poor investments, as they contain less-desirable grass types. High quality seed is well worth spending a little more for a lawn that can last a lifetime.
For sunny areas, choose seed containing 50 percent or more Kentucky bluegrass cultivars, as indicated on the label. Overseeding with a mix composed entirely of Kentucky bluegrass cultivars is also an option for thickening an existing thin lawn. For shaded areas, choose a mix containing about 80 percent fine fescues combined with Kentucky bluegrass.
To determine how much seed to spread, check the label for directions, which will tell how many pounds to apply for a given number of square feet. Measure the length and width of your lawn surface, and multiply together to find your square-foot area.
To spread grass seed, small areas can be scattered by hand. For overseeding an entire lawn, use a drop-type spreader, set according to the directions. When using a spreader, divide the seed quantity in half and go over the area first in one direction, then crisscrossing in the other. Slit-seeders are also effective for overseeding and can be rented.
Kentucky bluegrass takes two to three weeks to sprout. Keeping the lawn surface moist during that period will greatly enhance success.
When overseeding into existing thin grass, continue to mow the existing grass short for about a month. When the new grass matches the existing grass’s height, raise the mowing height to the recommended 3 inches.
Many lawns don’t need additional seed, but can be improved by fertilizing around Memorial Day, raising the mowing height to 3 inches, core aerating if compacted and watering deeply by applying at least 1 inch per week rather than frequent light sprinklings during dry periods.
Don Kinzler, a lifelong gardener, worked as an NDSU Extension horticulturist and owned Kinzler’s Greenhouse in Fargo. Readers can reach him at firstname.lastname@example.org.