Lolium arundinaceum, tall fescue is a cool-season perennial C3 species of grass that is native to Europe and introduced to California.

Most publications have used the names Festuca arundinacea or, more recently, Schedonorus arundinaceus for this species, but DNA studies appear to have settled a long debate that it should be included within the genus Lolium instead.

Tall fescue is a long-lived tuft-forming perennial with erect to spreading hollow flowering stems up to about 165 cm (5'6") tall (exceptionally up to 200 cm) which are hairless (glabrous), including the leaf sheaths, but with a short (1.5 mm) ligule and slightly hairy (ciliate) pointed auricles that can wrap slightly around the stem.

Flowering typically occurs from early June until late August, with an erect to slightly nodding open panicle up to about 40 cm (1'6") long.

The branches are normally in pairs, each of which has 3-18 spikelets, which are 9-15 mm long and comprise 4-8 bisexual florets and two short, unequal glumes.

In its native European environment, tall fescue is found in damp grasslands, river banks, and coastal area.

[12] Its Ellenberg values in Britain are L = 8, F = 6, R = 7, N = 6, and S = 1, which show that it favours damp, brightly sunny places with neutral soils and moderate fertility, and that it can occur in slightly brackish situations.

[15] This association between tall fescue and the fungal endophyte is a mutualistic symbiotic relationship (both symbionts derive benefits from it).

[22] Tall fescue was introduced into the United States in the late 19th century, but it did not establish itself as a widely used perennial forage until the 1940s.

As in Europe, tall fescue has become an important, well-adapted cool season forage grass for agriculture in the US with many cultivars.

This non-native grass is well adapted to the "transition zone" Mid Atlantic and Southeastern United States and now occupies over 35,000,000 acres (140,000 km2).

In 1943, Fergus and others recognized this tall fescue cultivar as being vigorous, widely adaptable, able to withstand poor soil conditions, resistant to pests and drought.

Broodmares that forage on infected fescue may have prolonged gestation, foaling difficulty, thickened placenta, or impaired lactation.

[27] To moderate toxicosis, it is recommended that pregnant mares should be taken off infected tall fescue pasture for 60–90 days before foaling as late gestation problems are most common.

Additionally, cattle may experience decreased weight gains and poor milk production when heavily grazing infected tall fescue pasture.

Many studies have suggested that long term endophyte-infected tall fescue plots increase soil carbon storage in the soil by limiting the microbial and macrofaunal activity to break down endophyte infected organic matter input and by increasing inputs of carbon via plant production.

[30] Site-specific characteristics, such as management and climate, need to be further understood to realize the ecological role and potential benefits of tall fescue and the endophyte association as it relates to carbon sequestration.

A widely used and tested novel endophyte is called MaxQ and is grown in the tall fescue grass host Georgia-Jesup.