Perennial Ryegrass (Lolium perenne L.)

Common Name: Perennial Ryegrass

Scientific Name: Lolium perenne L.

Synonym: An additional common name for perennial ryegrass is 'English ryegrass'.

Family: Poaceae

Tribe: Poeae

Origin: Indigenous to parts of Europe, Asia, and North Africa.

Time of introduction:
During colonial times, exact date uncertain; likely late 1700s.


Perennial ryegrass is a cool season perennial grass used in cool, temperate climates throughout the world. It has many worthy attributes and is considered the best overall pasture grass for many areas. The inflorescence is a spike with alternately arranged spikelets attached edgewise directly to the central axis. Leaves of perennial ryegrass are folded in the bud. Blades are bright green, prominently ridged on the upper surface, and sharply taper-pointed. Lower surfaces are smooth, glossy, and hairless. Leaf margins are slightly rough to the touch. Ryegrasses, in general, grow best on fertile, well-drained soils but perennial ryegrass can tolerate wet soils better than some other grasses. It also does not generally tolerate drought or extended periods of extreme temperatures well. Perennial ryegrass will do well in fertile summer-irrigated or sub-irrigated soils. It is not very persistent or productive on lower fertility summer-dry soils. Perennial ryegrass establishes rapidly, has a long growing season, is high yielding under good environmental conditions and proper fertilization, contains high quality nutrients, recovers well after grazing, tolerates traffic, and is valuable as hay, silage, and pasture. It is often used in mixtures with white clover. Perennial ryegrass is highly digestible for all classes of ruminant animals. Ryegrass staggers is an important disorder associated with perennial ryegrass. It is caused by a fungal endophyte, but monitoring crop development can help avoid problems.

Life cycle (annual/biennial/perennial):
Short-lived perennial. Seeds may live in the soil for quite a while.

Growth habit & Regrowth type:
Bunch growth habit. The shoot apex is positioned within the base of an enveloping leaf sheath. When conditions are suitable, the leaf primordia elongates to form a leaf, and the bud may form a new vegetative tiller. The shoot apex is transformed to a reproductive tiller if vernalization requirement (> 2 weeks at 39 F; 4 C or lower) has been met. Regrowth is culmless and tolerant of severe defoliation.

Invasive potential:
Low; no rhizomes or stolons, short-lived.



Image Gallery: The OSU Forage Information System contains an Image Gallery that includes Perennial Ryegrass photographs and drawings useful in identification. The URL for the gallery is:

The direct URL for Perennial Ryegrass is:

Inflorescence: The inflorescence is a spike 2 to 12 inches (5 to 30 cm) long. It has 5 to 40 alternately arranged spikelets attached edgewise directly to the central axis (rachis). Lemmas are awnless, in contrast to annual ryegrass. Perennial ryegrass inflorescence image.

Spikelets: Spikelets contain 3 to 10 florets. The terminal (end) spikelet has two glumes, but the inner glume is absent in the other spikelets. Perennial ryegrass spikelets image.

Seed: Lemmas of perennial ryegrass are awnless. In contrast, annual ryegrass is awned.

Seeds per pound average 237,000 (521,000 per kg), with a range of 200,000 to 265,000 per pound (440,000 to 583,000 per kg). Perennial ryegrass seeds are 0.2 to 0.3 inches long (5 to 8 mm), and width at the midpoint is 0.04 to 0.06 inches (1 to 1.5 mm). Perennial ryegrass seed image.

Stem: Flowering stems (culms) are comprised of nodes and internodes, each node bearing a leaf. Culms are 12 to 40 inches in height (30 to 100 cm) depending on variety, moisture, and site conditions. The uppermost culm segment is called the peduncle, the structure that supports the flowering parts. The stem base commonly is reddish. Perennial ryegrass stem image.

Leaf: Leaves of perennial ryegrass are folded in the bud (in contrast to those of annual ryegrass, which are rolled). Leaf blades are 0.08 to 0.25 inches wide (2 to 6 mm) and 2 to 6 inches long (5 to 15 cm). They are bright green, sharply taper-pointed, and keeled. Blades are prominently ridged on the upper surface. Lower surfaces are smooth, glossy, and hairless. Leaf margins are slightly rough to the touch. Blades increase in size from the first to the seventh leaf on a tiller, although tillers rarely have more than three live leaves at one time. Leaf sheaths usually are not keeled. They are compressed but sometimes almost cylindrical. Sheaths are hairless, pale green, and reddish at the base. They may be closed or split.

Collar: The collar, a narrow band of meristematic tissue at the junction of the blade and the stem, accounts for increasing blade length. Once the blade has achieved its maximum length, cells in the collar cease dividing. The perennial ryegrass collar region is narrow, hairless, and yellowish- to whitish-green. Auricles are small, soft, and claw-like. The 0.01- to 0.1-inch (0.25 to 2.5 mm) ligule is thin-membranous and rounded or toothed at the tip. Perennial ryegrass collar drawing.

Root: The shallow root system is highly branched and produces adventitious roots from the basal nodes of tillers. Perennial ryegrass has no rhizomes, though stolons have been reported. Perennial ryegrass root image.

Physiology and growth period:
Cool season (C3) species producing most of growth in spring and autumn. Perennial ryegrass has a long growing season with excellent persistence under close grazing and compatability with white clover. Growth in the fall continues longer than reed canarygrass, smooth bromegrass, orchardgrass, or timothy. Performs best under a high N status. Growth initiation temperature is 41 F (5 C). Growth stops at approximately 86 F (30 C), and optimum growth occurs at 68-77 F (20-25 C).

Both perennial and Italian ryegrasses are self-incompatible and cross-pollinated. Lolium species are interfertile, and will cross with Festuca species, including meadow fescue and tall fescue. Perennial ryegrass has an obligate vernalization requirement of at least 2 weeks at 39 F (4 C) or lower before inflorescence development will initiate.

Quality/anti-quality factors:
Quality of perennial ryegrass forage is excellent, with high levels of protein and digestibility. It is very palatable to all classes of livestock and wildlife.

Fungal endophyte/ryegrass staggers
Ryegrass staggers is an important disorder associated with perennial ryegrass. It is caused by a fungal endophyte (Neotyphodium lolii Latch, previously known as Acremonium lolii Latch). This is a different endophyte from the one associated with tall fescue.

This fungus does not harm the grass plant and is transmitted only by seed. In fact, the endophyte benefits the plant by producing toxins that impart resistance to several kinds of insects and diseases. Unfortunately, the same toxins cause adverse health effects in animals.

In the early stages, affected animals have difficulty flexing their legs and thus have an unusual gait. In severe cases, animals have difficulty walking and may fall repeatedly. Convulsions and death may occur. There is no treatment for ryegrass staggers except to reduce consumption of infected plants.

The symptoms of ryegrass staggers are worsened by excitement. If animals show symptoms, allow all the animals in that paddock to move to a safe paddock. Open the gate, move the salt, and allow the animals to move quietly on their own to the uninfected paddock. Don't drive them. Animals showing convulsions or inability to walk on their own should be quietly carried to a dark corner of the barn to eliminate noise and other stimuli. Give them uninfected forage and water to allow toxins to clear from their system.

The endophytic fungus is present only in seed head tillers and not in basal leaves. Thus, monitoring crop development can help avoid problems. The long-term solution to this problem may be the introduction of "novel endophytes" that produce specific chemical compounds that impart insect resistance without causing animal disorders. See Cheeke's book, Natural Toxicants in Feeds, Forages, and Poisonous Plants for more information.

Facial eczema
Facial eczema is a condition of severe dermatitis in cattle, sheep, and goats. Newly shorn sheep are especially vulnerable. It is caused by a toxin in spores of the saprophytic fungus Pithomyces chartarum (Berk. And Cart.) M.B. Ellis. In reality, the skin lesions are the secondary result of liver damage, rather than the direct result of the plant toxin.

The P. chartarum fungus grows in the moist, protected dead material at the base of forage plants, especially perennial ryegrass. Fungal growth is favored by warm, wet, humid weather, heavy dew, or irrigation. Intensive grazing practices increase the risk of facial eczema.

Animals suffering from facial eczema become restless and seek shade (photophobia). Growth and milk production are reduced dramatically. Typical symptoms of facial eczema include severely ulcerated skin in nonpigmented areas of the body. Other symptoms may include itching and rubbing of affected areas, scabs, loss of appetite, droopy and swollen ears, and swollen lips and eyelids.

Remove animals suffering from facial eczema from the contaminated pasture and provide them with shade, cool water, and a good diet. Feeding hay and/or grain reduces toxin consumption and maintains the animals until the skin lesions heal, and new, healthy liver tissue grows. (See Natural Toxicants in Feeds, Forages, and Poisonous Plants for more information.)



Perennial ryegrass is best adapted to temperate climates with mild winters and cool summers. It is less winter-hardy than orchardgrass and tall fescue and less drought-tolerant than smooth bromegrass. Studies in Wisconsin, however, suggest that perennial ryegrass is able to overwinter in colder climates, even where snow cover is unreliable. In the Pacific Northwest, perennial ryegrass will survive most winter weather conditions. However, during very harsh winters, it may winter kill. Thus, it should be considered a short-lived perennial.

Suitability zones:
Humid temperate regions with moderate winters. Its primary use for forage in the United States is in the Pacific Northwest. There also is considerable use in irrigated intermountain valleys, the Midwest, and the Northeast.


Grass is not very tolerant of prolonged drought or severly cold (<20 F; -6 C), open winters. Newer varieties have improved winter hardiness, but still suffer stand loss over time in Plant Hardiness Zones 4 and 5. Not suited for Plant Hardiness Zones 1-3 as depicted by the 1990 USDA Plant Hardiness Zone Map regardless of snow cover. Not suited to low fertility or droughty soils.

Quantitiative Table:

Max Temp (C)
Min Temp (C)
Precip (mm)
Soil pH Soil Drainage
Soil Salinity
Low High Low High Low High Low High Low High Low High
Well Adapted 22 32 -10 9999 550 9999 5.75 7.5 MWD MWD 0 2
Moderate 20 34 -15 9999 450 9999 5.5 7.75 SPD MWD 0 8
Marginal 18 36 -20 9999 350 9999 5.25 8.0 PD WD 0 8
1. For the High values for January Minimum temperature and Annual Precipitation: "9999 is entered to indicate no limit to the high values for this tolerance category."
2. For Soil Drainage categories, " Abbreviations are used for Soil Drainage categories: VPD (very poorly drained), PD (poorly drained), SPD (somewhat poorly drained), MWD (moderately well drained), WD (well drained), SED (somewhat excessively drained), ED (excessively drained)."

Climate: Perennial ryegrass is best adapted to cool, moist climates where winter kill is not a problem because it is less winter hardy than other grass species. Spring and fall are the seasons of best growth; during the hot summer months, perennial ryegrass becomes dormant. Maximum growth occurs between 68 and 77 F (20 to 25 C). Perennial ryegrass is adapted to shade in the warmer portions of a cool, humid climate. Perennial ryegrass is more sensitive to temperature extremes and drought than is annual ryegrass. Even with irrigation or abundant rainfall, production suffers when daytime temperatures exceed 87 F (31 C) and nighttime temperatures exceed 77 F (25 C). Its minimum precipitation range is 17 to 25 inches (450 to 650 mm). Perennial ryegrass is less winter-hardy than orchardgrass and tall fescue and less drought-tolerant than smooth bromegrass. Studies in Wisconsin, however, suggest that perennial ryegrass is able to overwinter in colder climates, even where snow cover is unreliable. In the Pacific Northwest, perennial ryegrass will survive most winter weather conditions. However, during very harsh winters, it may winter kill. Thus, it should be considered a short-lived perennial.

Soils: Perennial ryegrass grows best on fertile, well-drained soils, but is suited for use in soil drainage classes ranging from well drained to poorly drained. It will tolerate long periods of flooding (15 to 25 days) when temperatures are below 80 F (27 C). Perennial ryegrass tolerates both acidic and alkaline soils, with a pH range of 5.2 to 8.0. Best growth occurs when soil pH is maintained between 5.75 and 7.5. Perennial ryegrass is tolerant of salinity levels between 0 and 8 mmhos/cm.

Grazing Management: Cutting and grazing management greatly influences forage quality, productivity, and persistence. Quality is most affected by maturity stage at harvest.

Perennial ryegrass can withstand close, frequent grazing and thus is ideally suited for intensive sheep and cattle grazing systems. The diploid varieties in particular tolerate treading well.

Turf Management: For turf, perennial ryegrass is used alone or in combination with other grasses. Disease problems and limited cold and heat tolerance, however, limit its persistence and zone of adaptation. Recent improvements in turf varieties include improved disease resistance, heat tolerance, darker green color, and better mowing characteristics.

Be aware, however, that a fungal endophyte often is added to "turf-type" varieties of perennial ryegrass for increased pest resistance. The endophytic fungus produces toxins that can cause serious health problems for livestock. Use endophyte-infected varieties with caution, if at all, for livestock feed.

Pests: Diseases: In humid climates, perennial ryegrass is susceptible to ergot, which is toxic to livestock, and to stripe smut, which can cause grass to be unpalatable. Many varieties are susceptible to leaf spots, fusarium, brown blight, and other fungus diseases in hot, humid climates. Most varieties also are susceptible to snow molds, and many are susceptible to mildews of various sorts including powdery mildew.

In the northeastern and northwestern sections of the United States, crown rust, stem rust, and bacterial wilt can be problems depending on weather conditions and variety susceptibility. Stem rust often is a problem in late spring and early summer, especially if forage is allowed to accumulate. Stem and crown rust occur in late summer and early fall.

Although rust is not toxic to livestock, it can affect quality and palatability. For horses especially, the spores from rusts can cause significant respiratory problems. Maintaining high fertility and harvesting the accumulated forage reduce rust problems.

For turf and grass seed production, chemical control measures are available. Most, however, are not registered for forage use.

Pests: Insects: The grass grub is an important pest of ryegrass. Grub larvae eat ryegrass roots, rendering the plant more susceptible to drought. In New Zealand, the Argentine stem weevil is a major perennial ryegrass problem. Perennial ryegrass is resistant to this weevil (and other pests) if the grass is infected by the fungal endophyte. Presence of the endophyte, however, can cause a neurological disorder in livestock known as ryegrass staggers. See "Animal health/forage antiquality issues." The European cranefly (Tipula paludosa Meigen) is important in some parts of the Pacific Northwest. Chemical control measures are available, but seldom economical. Typically, pastures are renovated and reseeded when stands are lost to the European cranefly.

Pests: Nematodes: Perennial ryegrass is susceptibile to root lesion nematodes.


Scores of turf-type and forage-type cultivars are listed in the "Grass Varieties in the United States" publication. These have been cataloged in the Forage Information System Cultivar Database.


Perennial ryegrass can be seeded in spring or late summer. In addition, it may be fall-seeded in areas with mild winters. Perennial ryegrass may be seeded alone or with associated forage species. Seeding may be done in a clean, well-prepared seedbed in existing sod with a sod-seeder or grassland drill. It is common practice to drill ryegrass in standing stubble. Under favorable conditions the species will germinate and emerge quickly.

Seeding rate:
When seeded alone, the seeding rate for perennial ryegrass forage applications is typically 18-20 lbs/acre (20-22 kg/ha). When broadcasting, increase seeding rates by 50 percent or more, depending on seedbed condition. Reduce seeding rates by 30 percent for well-prepared seedbeds for irrigated production in the intermountain West.

When renovating, mow or graze the existing sod short to reduce competition. A non-selective herbicide may also be used to reduce competition for renovation.

Seeding depth:
Seeding depth should be between 0.25 and 0.5 inch (0.6 to 1.25 cm). When seeding with legumes, 0.25 inch (0.6 cm) is preferred.

Fertilization and liming:
Perennial ryegrass requires high fertility levels for good production. Fertilization should be based on a soil test. Obtain specific recommendations from extension nutrient management guides.

Perennial ryegrass is very responsive to nitrogen (N) fertilization. For each pound of N added (up to 250 to 400 lb/a/yr or 280 to 448 kg/ha/yr), per-acre yields of dry matter increase by 20 to 30 lb (22 to 34 kg/ha). At higher rates, the yield increase from each pound of additional fertilizer N declines. Typically, the maximum economic level of annual N fertilizer is approximately 160 lb N/a/yr (180 kg N/ha/yr).

Applications of total yearly N should be split as evenly as possible to meet the continuing need for nitrogen throughout the growing season. Make the first application at the beginning of the season and the others after each harvest except the last. This pattern produces greater annual yield and better quality forage than does a single, early spring application.


Perennial ryegrass is grown primarily for pasture and silage. It can be grown for hay, but typically will provide only one hay cutting and little regrowth due to sensitivity to dry soil and high temperature conditions. It also is used for reducing soil erosion, recycling nutrients from manure and biosolids, wildlife feed, and turf.

Seed crop:
Nearly 100% of US perennial ryegrass seed production occurs in Oregon. Approximately 160,000 acres (64,800 hectares) is planted for seed production, resulting in 250 million lbs (113.5 million kg); 156.25 lb/acre or 175.15 kg/ha.

Perennial ryegrass is considered the premier-quality pasture grass throughout the world, having higher digestibility than other temperate, perennial grass species. Tetraploid varieties (those having four sets of chromosomes) have slightly higher digestibility than diploid varieties (with two sets of chromosomes).

Because of its high quality, perennial forage-type ryegrass is used primarily for lactating dairy cows on pasture. However, it is suitable for all classes of livestock, especially those with high nutrient requirements such as young, growing animals. Currently, lack of persistence and sensitivity to high temperature and drought are the main limitations to expanded use for pasture in the United States.

Silage and Hay
Perennial ryegrass often is harvested for silage. It makes up a considerable portion of dairy-quality grass silage in coastal regions of the Pacific Northwest. As with all forage species, silage quality is influenced greatly by maturity stage. For the optimal compromise between quality and quantity, cut perennial ryegrass in the boot stage.

Harvesting perennial ryegrass for hay is not recommended in high rainfall/humidity areas such as the coastal Pacific Northwest. Good hay curing weather typically occurs too late in this region for producing high-quality ryegrass hay.

Erosion Control/Conservation:
Perennial ryegrass is well suited to soil conservation uses. Its extensive, shallow, fibrous root system makes it effective for reducing soil erosion. It is recommended for use alone or as a fast-starting component in mixtures, where it provides rapid cover and allows longer-lived or more winter-hardy species to become established.

Manure and biosolids application
High growth rates under high fertility and an extensive root system make perennial ryegrass valued for use in nutrient recycling systems. Highly productive grasses such as perennial ryegrass can utilize 300 to 400 lb of nitrogen (N) per acre (336 to 448 kg N/ha) per year from livestock manure or biosolids. This ability to use large quantities of nitrogen results in high-quality forage and protects groundwater from contamination through leaching of unused nitrate.

Wildlife habitat and feed:
Perennial ryegrass also is useful as wildlife feed. Geese, coots, widgeons and other ducks, wild turkeys, rabbits, deer, and elk graze this forage. Quail and songbirds such as the white-crowned sparrow, golden-crowned sparrow, Savannah sparrow, and brown towhee feed on seeds, as does the pocket mouse.

Use of perennial ryegrass for turf has increased in recent years with selection of more dense-growing and persistent turf types. It is one of the most versatile turfgrass species.

Economic value:

The approximately 160,000 harvested acres of seed production produce 250 million pounds with a farm gate value of $137.5 million, wholesale value of $171.875 million, and retail value of $240.625 million.

Due to high yield, forage quality, and palatability, perennial ryegrass is highly valued as a feed for dairy cattle and sheep. Throughout the world, it is the premier forage grass for irrigated pastures, typically combined with white clover.

In the USA, primary adaptation and usage of perennial ryegrass for forage is in the Pacific Northwest, though there is considerable use in irrigated intermountain valleys, the midwest, and the northeast. Estimated perennial ryegrass forage production was provided by Balasko et al. (1995) at 123,500 acres (50,000 ha) each for the Pacific Northwest and northeastern areas. For the midwest, the estimate is 20,000-25,000 acres (8,000 to 10,000 ha). Combined that's approximately 275,000 acres (111,375 ha). If each acre produced 4 tons of dry matter (8,000 lbs) and was valued at $75 per ton ($300 per acre), that would be a total value of $82.5 million for perennial ryegrass forage.

Soil and water conservation:
Green values are difficult to quantify. Nevertheless, due to its rapid germination and ease of establishment, perennial ryegrass often is included in soil conservation mixtures to stabilize soil and promote water infiltration. Its extensive, fibrous root system makes it effective for reducing surface soil erosion.

Perennial ryegrass is planted as permanent turf in northern areas and is overseeded into warm season turf in the south. Total perennial ryegrass turf plantings represent 40% of the approximately 50 million acres of lawn area. Planted at 100-300 lbs per acre, this creates a large seed market and economic value.


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  2. Barnes, R.F., M.E. Heath, and D.S. Metcalfe. 1973. Forages: The Science of Grasslands Agriculture. Third Edition. 29:307-313. Iowa State University Press. Ames, IA.
  3. Cheeke, P.R. 1998. Natural Toxicants in Feeds, Forages, and Poisonous Plants. Second Edition. Interstate Publishers, Inc. Danville, IL.
  4. Cool-Season Forage Grasses. 1996. American Society of Agronomy monograph No. 34. ASA, CSSA, SSA, Madison, WI. 841 pp.
  5. Forage Information System [Online]. 2004. Oregon State University. Corvallis, OR. Available at (verified 12 July 2004).
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  7. Perennial Ryegrass (Lolium perenne L.). 1999. Oregon State University. PNW Exten. Circ. 503. Corvallis, OR. Available at (verified 12 July 2004).
  8. USDA, NRCS. 2004. The PLANTS Database, Version 3.5 [Online]. National Plant Data Center, Baton Rouge, LA. Available at (verified 12 July 2004).

Marc Cool, Barenbrug - USA
David B. Hannaway, Christina Larson, and Daniel Myers, Oregon State University

Document creation:
4 June 2004

Last update:
16 August 2004

James B. Cropper, Natural Resource Conservation Service (NRCS)
Keith Johnson, Purdue University (Not contacted yet)
Marty Chaney, Natural Resource Conservation Service (NRCS)

Review date:
22 June 2004 (Cropper)
07 July 2004 (Chaney)