Everything You Need to Know About Perennial Ryegrass

Perennial ryegrass (Lolium perenne) is a fast-germinating, cool-season grass often grown year-round in Northern climates. In Southern climates, perennial ryegrass can be overseeded to add color to warm-season lawns that go winter-dormant and brown. It gives those lawns a quick “green-up" and then dies when temperatures rise and warm season grasses start growing again.

What is Perennial Ryegrass?

Native to Europe, Asia and Northern Africa, perennial ryegrass is an attractive, durable and widely used turfgrass. It germinates as quickly as five days after sowing and grows into a stand of glossy, green blades. This easy-to-grow grass tolerates cold, holds up to heavy foot traffic and helps control erosion. Old varieties were often vulnerable to drought and diseases, but newer ones have more resistance and drought tolerance; some use up to 30 percent less water each year (and perennial ryegrass traditionally needs a lot of water). Unless you specifically want a common or forage-type perennial ryegrass, look for these improved varieties, which produce a high-quality lawn. Not sure what kind of grass you want? There are different types of perennial grasses to choose from.

Unlike annual ryegrass (Lolium multiflorum), perennial ryegrass comes back every year when given proper care. Thanks to its durability, rye is a popular choice grown around the U.S. on sports fields and golf courses and in pastures where animals forage. Both annual and perennial ryegrasses are considered winter grasses.

Warm-season grasses are more common in warmer climates, but they turn brown and go dormant when the temperatures drop. To keep their yards green, lawn owners often overseed their existing grass with perennial ryegrass seeds. When the temperatures go back up, the warm-season grasses start growing again and the perennial ryegrass dies out.

Perennial ryegrass is sometimes called a “nurse” grass because it can be mixed with slower-germinating grass seeds to shade them until they’re established. Perennial ryegrass can tolerate temperatures up to about 90 degrees F. It's a good choice for growing in the transition zone, an area that runs through the middle of the U.S. where cool- and warm-season growing conditions meet and other grasses often struggle. Your county extension service agent or a lawn care professional can help you find the right grass for your area.

One note: perennial ryegrass grass is not the same as cereal or winter rye (Secale cereale L.), which is planted in the fall for erosion control or to use as a cover crop or early-season forage crop.

When to Sow Perennial Ryegrass Grass Seed

Most people plant perennial ryegrass seeds. Before you begin sowing or overseeding, aerate your soil if it's compacted. Then test it and add amendments if indicated; for best results, mix them into the soil several months before planting. Perennial ryegrass needs a pH of 5.5 to 7.5 and well-draining, fertile soil. While it thrives in full sun, it can also tolerate light shade.

How to Grow Perennial Ryegrass in Cool Climates

The best time to sow perennial ryegrass seeds is in the late summer, early fall or early spring, when the ground is moist and the weather is relatively mild. Perennial ryegrass seedlings grow fast into a lawn that may need to be mowed as soon as 21 days after sowing.

After you've aerated, tested and amended the soil, clear away leaves and other debris and rake the soil to loosen it. Level it and sow the seeds 1/4 to 1/2-inch deep. For new lawns, sow about 3 to 5 pounds of seeds per 1,000 square feet. Cover the seeds lightly with soil or compost and water them. Keep them consistently moist, watering daily or multiple times each day, until the perennial ryegrass grass is about three inches tall. Then cut back to watering once a week.

How to Grow Perennial Ryegrass Lawns in the South

If you’re overseeding a warm-season grass that goes winter-brown and dormant, mow the existing grass short and remove the clippings. Sow about 5 to 10 pounds of perennial ryegrass grass seeds per 1,000 square feet, or 10 to 15 pounds per 1,000 square feet for a dense, lush look. To help the seeds make good contact with the ground, run a stiff brush over the existing grass to knock them down or gently rake them in.

As with newly-sown perennial ryegrass seeds, cover the seeds lightly with soil or compost and water them. Keep them consistently moist until the seedlings are three inches tall, and then cut back to watering once a week.

How to Maintain Perennial Ryegrass

Perennial ryegrass grows in bunches or clumps that have shallow roots. Because it spreads slowly through vertical shoots called tillers, unlike grasses that spread by underground stems (rhizomes) or above-ground stems (stolons), this bunch-type grass can look patchy or thin in spots.

"Most perennial ryegrass lawns need about one inch of water per week," says Don Chouinard, Principal Pro Account Manager at Irrigreen, a company that produces smart, in-ground irrigation systems. He recommends splitting that watering into two or three days a week. "Every time you water deeply, you are training the root system to chase that moisture as it moves through the ground, which builds a stronger, healthier, more resilient lawn.''

Perennial Ryegrass Pros and Cons

The benefits of perennial ryegrass include:

- Germinates and establishes quickly
- Tolerates partial shade
- Adds green color to winter-dormant lawns
- May stay green all year in cool climates, especially in the Pacific Northwest
- Wear-resistant

Some cons of perennial ryegrass are:

- Needs lots of water, fertilizer and mowing
- Low tolerance for heat and drought
- May go dormant or die, even in Northern climates, at extremely high or low temperatures
- Doesn’t self-repair (that is, fill in bare spots, like grasses with runners or rhizomes)

Care Calendar for Perennial Ryegrass

In spring: Sow perennial ryegrass seeds when temperatures are between 50 and 65 degrees F. Once the grass is actively growing, apply 2 to 4 pounds of nitrogen (N) per 1,000 square feet or, ideally, use the amount indicated by your soil test. Don’t apply it all at once. Divide it into two to four smaller amounts and apply some in spring and some in fall. Do not apply nitrogen during the hot months.

If you’re overseeding, wait until after your second mowing to apply 1/2 pound of nitrogen per 1,000 square feet or the amount shown on your soil test.

Start mowing new or overseeded areas when the grass is 1-1/2 to 2-1/2 inches tall. Bag and discard the first clippings in case fungal diseases are present. If you expect weeds and crabgrass to be a problem, use a pre-emergent herbicide. Start fertilizing monthly. Read and follow the directions on all product labels; you may need to wait a few weeks before using herbicides and fertilizers. The grass needs at least one inch of water per week, so water it if rain is scarce.

In summer. When you mow, don’t remove more than 1/3 of the grass blades at one time. Keep your blades sharp to make clean cuts. Let the grass grow 3 to 4 inches tall in hot, dry weather. When you mow an overseeded area, mow to the height recommended for the warm-season grass that’s been overseeded. Increase watering to 1-1/4 inches of water weekly. In general, stop fertilizing when it's hot and dry.

In fall. As weather cools down, mow the grass to 1-1/2 to 2-1/2-inches tall. Mow until it stops growing. This is one of the best times to plant or overseed. In Northern climates, sow the seeds 45 days before the average first fall frost. In Southern climates, overseed when your warm-season grass starts to go dormant and overnight air temperatures are about 65 to 70 degrees F.

In winter. Keep the grass free of leaves and other debris. In Northern areas, flush perennial ryegrass with water in late winter, when the soil thaws out, to remove deicing salts or other pollutants.