Flower:

A single erect spike to 12 inches long at the tip of the stem, with a single spikelet (flower cluster) at each node, arranged alternately on opposite sides of the stem. Spikelets are stalkless, flattened, appressed to ascending, rotated so the edge of the spikelet is against stem (rachis) rather than the flat side. The rachis is grooved on the side facing the spikelet and smooth-textured on the opposite side. Each spikelet is 5 to 22 mm (to ~.9 inch) long (excluding any awns) and has 4 to 10 florets, rarely more; the uppermost floret(s) may be sterile.

At the base of a spikelet is a single bract (glume) that is leathery, 5 to 7-veined, not keeled, hairless, lance-elliptic, blunt to pointed at the tip, awnless, and about as long as or longer than the adjacent floret, often over-topping it; only the terminal spikelet has a pair of glumes. Florets are surrounded by a pair of bracts (lemma and palea), the lemma hairless, 5-veined, 3.5 to 9 mm long, not keeled, blunt at the tip, mostly awnless but some with a straight awn up to 8 mm long; the palea is more or less as long as the lemma.

Leaves and stems:

Leaves are alternate, ascending to spreading, up to 12 inches long, 2 to 6 mm (to ¼ inch) wide, flat and hairless. The sheath is hairless and may or may not have a pair of small brown lobes (auricles) at the sheath apex. The ligule (membrane where the leaf joins the sheath) is 1 to 2 mm long, jagged across the top edge, and lacks a fringe of hairs. Nodes are hairless. Stems are unbranched, smooth, usually erect, multiple from the base, forming loose clumps. Leaves of new shoots are folded lengthwise.

Fruit:

Any awns remain straight as spikelets mature, all turning bleached tan when dry. Florets drop off individually at maturity leaving the glumes behind on the stem.

Notes:

Perennial Ryegrass, native to Europe, Asia and north Africa, is commonly included in turf grass seed mixes, as well as being used for forage and erosion control. Besides lawns, it is most often found on roadsides but can show up in virtually any area subject to soil disturbance. It is likely under-reported in Minnesota, though determining whether a given population was intentionally planted or not is anybody's guess.

There are two Lolium species known to be in Minnesota, the other being Lolium multiflorum (Annual Ryegrass), and it is not always easy to distinguish them; the two are even considered different vars of the same species in some references (L. perenne var. multiflorum or var. aristatum, and var. perenne). Lolium in general is fairly distinct with the spikelets rotated so the edge is against the stem (rachis) and only the terminal spikelet has two glumes. Vaguely similar are some Elymus species, notably Quackgrass, which has the flat side of spikelets against the stem and a pair of glumes on all spikelets.

L. perenne is distinguished by a grooved rachis that is smooth on the surface, spikelets usually having 5 to 10 florets, the glume about as long as or longer than the adjacent floret, lemmas awnless or having an awn less than 8 mm long, sheaths lacking auricles or with poorly-developed auricles, and leaves of new shoots folded lengthwise. By comparison, L. multiflorum has a rachis that is rough-textured on the surface, spikelets have 10 to 20 florets, the glume is shorter than the adjacent floret, most lemmas have awns up to 15 mm long, sheaths have well-developed auricles, and leaves of new shoots are rolled in along the edges. A third Lolium species, L. temulentum, is present in Iowa and may also be in MN; it has a particularly long glume, even over-topping the uppermost floret.