Perennial ryegrass

What is perennial ryegrass?

Perennial ryegrass (Lolium perenne) is a cool-season bunch grass that came from Europe, Asia and Africa. It looks a lot like Kentucky bluegrass in color and texture, which is why the two are often sown together.

Its claim to fame is speed. Penn State says the seed comes up in 5 to 7 days, far faster than bluegrass. That makes perennial ryegrass grass the usual pick for overseeding worn sports fields and thin lawns. Several turf varieties also carry endophytes, helpful fungi inside the plant that raise resistance to several leaf-feeding insects.

Its weak points are that it does not spread and can be short-lived. It has no rhizomes or stolons, so it recovers slowly. It gets several diseases, and dull mower blades shred the tips and give the lawn a gray cast (Penn State). On poor or acidic soil it gets thin and clumpy.

How to identify perennial ryegrass

Pull up a few shoots and look closely where the leaf blade meets the stem. Here is what to check on perennial ryegrass:

• Vernation: Folded in the bud.
• Ligule: Thin membrane, collar-like to blunt, may be toothed at the top, 0.5 to 1.5 mm (0.02 to 0.06 in.) long.
• Auricles: Small and stubby (rudimentary).
• Collar: Distinct, split by the midrib, not hairy.
• Leaf tip: Sharp-pointed.
• Leaf blade: 2 to 5 mm wide. Top is creased and deeply ridged; underside is smooth and glossy. Penn State notes a main midrib plus many small lengthwise veins.
• Sheath: Usually flattened and reddish at the base.
• Seedhead: A spike with flat spikelets set along the stem.
• Growth habit: Bunch-type; no rhizomes or stolons.

Where perennial ryegrass is grown in the US

In the North, perennial ryegrass is mostly a team player. Penn State lists it for lawns, parks, grounds, golf courses and athletic fields, and it is the standard grass for overseeding thin or worn turf because it sprouts so fast. Penn State says to keep it at no more than 20 percent of a seed mix because it can crowd out the other grasses.

In the South it is a winter grass. NC State uses it to overseed golf fairways, tees, sports fields and high-profile lawns where people want green color in winter. It usually dies out when warm weather arrives in late spring or early summer. NC State says that in North Carolina it is never seeded alone but always mixed with other grasses such as Kentucky bluegrass.

Colorado State covers it as a lawn option but ranks it last for staying power under low care. For mixes suited to our area, see our Pennsylvania grass seed guide.

Perennial ryegrass pros and cons

Pros

• Sprouts in about 5 to 7 days and fills in fast
• Takes heavy wear
• Blends well with Kentucky bluegrass in color and texture
• Endophyte varieties resist several lawn insects
• Low thatch

Cons

• Does not spread; slow to recover from damage
• Prone to brown patch, Pythium blight, dollar spot, red thread and rust
• Shredded, gray tips if mower blades are dull
• Easily hurt by ice cover
• Too aggressive if it is more than about 20 percent of a mix
• Colorado State ranks it lowest for staying power under low care
• Often sends up unsightly seed stems in late spring (University of Minnesota)

Grasses that look like perennial ryegrass

How and when to plant perennial ryegrass

Ways to plant: Seed. Colorado State notes it is not sold as pure sod.

Seeding rate: 4 to 5 lb per 1,000 sq ft when used alone (Penn State, turf types). Colorado State lists 6 to 8 lb. In mixes, keep it to 10 to 20 percent.

Germination: 5 to 7 days (Penn State).

When to plant: In the North, seed in late summer to early fall; Purdue gives Aug. 15 to Sept. 15 as the best window for cool-season seed. In the South it is sown over warm-season turf such as bermudagrass for winter color (NC State).

Seeding dates change from state to state. See when to plant grass seed by state, or our Pennsylvania grass seed guide if you are in PA.

How to care for perennial ryegrass

Mowing: Mow lawns at 1.5 to 2.5 in. (Penn State). Keep blades sharp; dull blades shred the leaves and leave a gray cast.

Watering: Colorado State says it handles drought well only when it is deep-rooted in well-prepared soil. UMass rates its drought tolerance poor.

Fertilizing: About 3 lb of nitrogen per 1,000 sq ft per year in Pennsylvania (Penn State). It does best on moderately to highly fertile, well-drained soil and gets thin and clumpy on poor or low-pH soil.

Nitrogen per year: About 3 lb N per 1,000 sq ft per growing season in Pennsylvania (Penn State). UMass lists about 2 to 4 lb.

Overseeding: This is its main job. Penn State uses 2 to 5 lb per 1,000 sq ft of turf-type ryegrass to renovate worn turf. UMass uses 6 to 8 lb for heavy-wear areas that are more than half bare. In bluegrass mixes, Purdue keeps it to 10 to 15 percent.

Thatch: Low. It builds thatch more slowly than Kentucky bluegrass and fine fescues (Penn State).

Common perennial ryegrass problems

If a pesticide is needed, use only products labeled for that use; the label is the law. If you hire someone to treat a lawn, make sure they hold your state’s pesticide applicator license; see our pesticide applicator license guide. To put a name to a lawn weed, use our weed identification guide.

Questions we get about perennial ryegrass

Similar lawn grasses

Kentucky bluegrassPoa pratensisSupina bluegrassPoa supinaTall fescueLolium arundinaceum