How to Overseed Your Lawn

What, how, and why to do so now – dormant seeding.

You’ve spent the spring and summer mowing, weeding, fertilizing, and edging your lawn. Now as winter sets in, you want to think you’re done for the season.

Not so fast! The billbugs and sod webworms have taken a toll on your lawn. There’s now work to do if you want that thick carpet of grass next spring.

Dormant seeding is a method of reseeding in cool soil, just before the cold weather sets in. It works best when snow quickly covers the seeds, letting them sleep until the soil warms again in spring.

USDA zones are guidelines to determine what kind of plants grow in various climates and topography. Colorado’s U. S. Department of Plant Hardiness Zones are from 3a to 7a – an average extreme temperature range of 35 degrees below zero to zero. Colorado’s climate yields average low temperatures in the upper teens during the winter. Reseeding in late October to mid-November keeps you from having to prepare the soil when it’s wet and cold during the spring.

Where to Dormant Seed

Dormant seeding works best on bare dirt areas, thin lawns, and dead spots. It won’t work as well on thick, dense grass because it’s harder for the seeds to germinate in solid turf.

When to Start

Timing is everything. If you overseed too early, some of the grains will germinate late in the growing season, leading to tender seedlings that will die in winter. Growing your lawn from seed is best done in spring or fall. But when it comes to dormant reseeding, sow before the ground freezes. It’s still cool enough to keep the seeds from germinating. Late October to mid-November is best.

Seeding

Chances are, your Colorado lawn is made up of one type or a blend of cool-season grasses. Most consist of Kentucky bluegrass, fine and tall fescues, and perennial ryegrass. Choose seed products that adapt to your lawn’s soil pH, sunlight, and how well it absorbs water. Just about any cool-season grass seed mixture is good for dormant seeding.

Once you’ve tested the soil, bought the seeds, and have your tools, you’re ready to begin.

  • For small areas: Loosen the earth’s surface with a hand rake and then plant the seeds about a quarter-inch deep.
  • For large bare areas: Use a power rake or vertical mower and set the blades to penetrate the top quarter-inch of soil. Raking the soil helps loosen thatch. Remove the debris before seeding.
  • Till in the grass seed lightly with a hand rake.

Water

Watering the grass is something you may not think you have to do in autumn. After all, the lawn is dormant. But if you want seeds to germinate in the spring, they must have water to drink. The fresh seeds won’t need much; about one-fifth to one-10th of an inch of water, along with cooler temperatures, will keep the seeds moist. Keep an eye on the amount of moisture the grass receives. DON’T overwater the new seeds at the outset — fall rains and winter snows will bring enough hydration to dormant lawns.

In the Spring

Colorado’s winter weather will determine the success of your overseeding. The soft layers of snow that cover reseeded areas should be enough to protect the seeds. The seedlings should begin to germinate by late April or early May.

Newly-seeded areas may be a bit thin, and you may have to add a few more seeds in the spring. This is common. But take your time and don’t tear up the sod before new seedlings have a chance to sprout through. Some are latecomers. If it becomes apparent that the dormant seeding did not work, you can always try again in the spring.

Dormant overseeding helps get rid of the bare spots, thicken turf, and fight any early weeds that crop up. But remember, if you overseed, you cannot use a pre-emergent herbicide for killing off weeds and crabgrass. It will kill the new grass seeds, too.


Bill Campbell is a landscaper and gardener who’s been mowing lawns since he was 14. He prides himself on being eco-friendly and maintains a green lawn without using chemicals.