Mostly short-lived perennial; culms slender, 3-9(-12) dm; spike slender, 1-2 dm, the rachis scabrous on the margins and sometimes also on the back; spikelets (2-)5-22-fld; glume 4-12 mm, herbaceous, distinctly shorter than the spikelet; lemmas awned or awnless, the lowest 5-8 mm, the upper progressively reduced; 2n=14, 28. Native of Europe, cult. in meadows and lawns and often escaped onto roadsides and in waste places throughout our range and w. to the Pacific. Two well marked but wholly intergradient vars., apparently originating as agronomic strains.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Common Name: perennial ryegrass Duration: Perennial Nativity: Non-Native Lifeform: Graminoid General: Perennial with stems to 100 cm, erect to decumbent at base. Vegetative: Blades dark green, glossy, 10-30 cm long, 2-4 mm wide, smooth to slightly scabrous above. Inflorescence: Spikes 3-30 cm long with 5-37 spikelets, spikelets 5-22 mm long, 1-7 mm wide with 5-9 florets that are appressed to erect-spreading, rachis 0.5-2.5 mm thick at nodes, flattened, scabrous on angles; glumes 3.5-1.5 mm, half to three-quarters as long to exceeding the upper florets; lemmas 3.5-9 mm long, 1-2 mm wide, awnless or with a minute tip. Ecology: Found in disturbed sites, widespread, introduced via cultivation; flowering May-September. Distribution: Introduced to every continent and found throughout N. Amer., in every state in the US. Notes: Distinguished by the flattened spikelets which are ranked alternately up a spike with the side towards the rachis lacking a glume and fitting into a groove in the rachis. Recent reorganization places this and other species previously in Lolium within Festuca, but this is inconsistent with other work. This treatment follows Tropicos, which still maintains this species as is. There have been ssp. multiflorum identified within the park, but there is not clarity in FNA or Manual of North American Grasses that this is separable from Lolium multiflorum, an annual to short-lived perennial non-native. Ethnobotany: Unknown Etymology: From Latin lolium for cockle, also the classical name for rye, while perenne means perennial. Synonyms: None Editor: SBuckley 2010, 2011, FSCoburn 2015
From Flora of Indiana (1940) by Charles C. Deam
This species is doubtless sparingly found throughout the state. It has been sown intentionally as an adulterant of grass seed in meadows and lawns. It is now found as an escape along roadsides, on the unkept borders of lawns, and in waste places. Besides one small colony which I have seen, I have no evidence to indicate that it is more than an occasional escape. Usually known in commerce as English Ryegrass.
Indiana Coefficient of Conservatism: C = null, non-native
Wetland Indicator Status: FACU
Deam (1929): This grass is extemely variable, due no doubt its being under cultivation for more than 200 years. It was probably first cultivated in England where it has always held an important place as a forage crop. I find no evidence that it was ever cultivated in Indiana for hay or pasture.