Planting grass seed can seem a little like witchcraft to the uninitiated. While turf arrives more or less pre-planted and rolls out as easily as carpet, planting seed requires coaxing vibrant, living grass from bare dirt.
Grass seed is almost always cheaper than turf, and can often result in better-established and more resilient lawn grass. But if the prospect of planting your own lawn still feels intimidating, you're not alone. There are many factors that go into successful seed planting, ranging from the weather to your garden’s incline to plain luck.
The good news, however, is that planting grass seed is easier than you'd think once you're armed with the right information. Today, let's take a closer look at a question that intimidates many new planters. Namely, when's the best time to plant grass?
The Best Time of Year to Plant Grass Seed
Grass falls into two broad categories: cool weather and warm weather. And as those category names suggest, these grasses handle the seasons differently.
Cool Weather Grasses
Cool season grasses—such as fescues, Kentucky Bluegrass, and ryegrass—do best with Autumn planting. Air temperatures should be between 10 and 18 degrees Celsius. Start seeding at least 45 days before your area’s typical first autumn frost.
Cool-weather varieties do their best when sown in autumn for a number of reasons. The soil temperature will still be warm enough for them to germinate, but they won't face the stress of dry and hot mid-summer days. After early autumn germination, they'll have a prime window for strong growth and development throughout the rest of the Autumn and early winter.
While you'll definitely see evidence of that growth as leaves grow above the soil, the real magic is happening underground. A strong, long-lasting lawn thrives on a well-established root system. Cool weather gives your new seeds plenty of time to grow one.
Planting in autumn also limits how much your seedlings will have to compete with weeds for space. The prime summer growth period for weeds will already be fading, and your cool-weather seeds will be better prepared to come out on top.
Cool-weather grasses can stay bright green through cold months, providing a welcome burst of colour to your garden. However, they are not well-suited to high heat and dry conditions. Be prepared to water your seeds frequently during hot summers.
Warm season grasses are less common in the UK. These grasses include St. Augustine grass, Zoysia grass, and Bahia grass.
Warm-weather grasses germinate best at 27 degrees Celsius or higher. Spread their seeds at least 90 days before your estimated first autumn frost.
Spring—with its moist soil and warming days—is generally the best time to sow. Warm weather seedlings fare badly through cold snaps, so always wait until frost risk has totally passed.
With these types of seeds, soil temperatures need to be consistently around 10oc for 3-5 days in a row. In the UK this is typically April onwards.
For the same reason, seeding these varieties in autumn is a bad idea. A well-established warm-weather lawn can survive cold winters, but only if seeds have had time to mature beforehand.
Warm-weather lawns tend to go dormant and brown in cold weather. Periods of extreme cold can even damage the lawn, leaving bare patches when warm weather returns.
Mixing Grass Varieties
Many parts of the world—including parts of the UK—experience a mix of weather conditions that sometimes accommodate warm-weather varieties and sometimes accommodate cool ones. Cool-weather varieties adapt to heat better than warm-weather varieties adapt to the cold. So if you're a UK lawn grower, you'll want to depend on cool-weather seeds.
However, there are reasons you may want to mix up your lawn seed. If you're noticing bald patches in your cool-weather spring lawn, new cool weather seeds will struggle to cover them up through the summer. Instead, try filling patches in with warm-weather varieties. When autumn comes, reseed with cool-weather seeds.
Two kinds of cool-weather seeds may still run on different germination schedules and tolerate moisture, shade, and temperature conditions differently. Lawn professionals can work with you to find the best seed variety—or seed mixture—to fit your garden’s conditions.
Other Scheduling Considerations
We've covered the best time of year to sow grass seed. But once you've settled that question, you should still take other factors into consideration:
The Weather Forecast
What does the weather look like for the next week or two? Keep an eye out for any cold snaps or heat waves, but look at precipitation, too.
Seeds germinate best in soil that's warm and moist—not soaked. Your seeds may simply rot in water-logged soil. And even a minor rainstorm can wash seeds sitting on a bare lawn away.
If torrential rain is in the forecast, hold off on planting until it's passed. If you're worried that your garden may be too dry for germination, you can use a hose to gently water your soil. Use a fine mist setting to moisten the top layer without disturbing your seeds.
Seeding your lawn can be a gratifying activity, leading to a lush, well-established garden. But it's also a fair bit of work. If you're seeding your lawn by yourself, keep that commitment in mind.
You'll have to prepare the soil by scrubbing or raking your lawn of existing weeds and their root systems. The actual sowing requires making many passes with a seed spreader. Some steps, such as applying fertiliser, should take place a few days before actual planting.
Your newly sown seedlings will be at their most delicate while they're germinating and beginning to sprout, which means it's a bad time for kids to play on the lawn.
You'll have to be vigilant about keeping your newly planted lawn moist (but not waterlogged) and eliminating new weeds. If patches of lawn don't sprout after the germination period listed on the seed packet has passed, you'll need to re-sow those areas.
Seeding your lawn is by no means gruelling or beyond the skills of a home gardener. But plan your schedule to sow a new lawn ahead of time. Don't tackle this project the same week you have a big assignment due at work.
Your Weedkiller Application
Seeds and young grass plants are delicate, and they don't handle weed killer as well as a mature lawn. Depending on the herbicide you used last, you may need to wait weeks or even months before planting grass seeds. Don't apply any herbicide products again until your new lawn has matured and been mowed a few times.
Experts Can Help
Still have questions about the best time to plant grass or lawn care in general? Lawn experts can give you valuable advice.At Grass Science Seeds, we use our industry expertise to create high quality seed mixes for all kinds of UK lawns. We're happy to talk to you about what your lawn needs and when to plant grass seed. Contact us today to learn more.