Tall fescue was introduced into the United States in the late 1800s, 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. In addition to forage, it has become an important grass for turf and soil conservation. This non-native grass has become well adapted to the southeast US and now occupies over .
The dominant cultivar grown in the United States is Kentucky 31. In 1931 E. N. Fergus, a professor of agronomy at the University of Kentucky, collected seed from a population on a hillside in Menifee County, Kentucky although formal cultivar release did not happen until 1943. Fergus heard about this "wonder grass" while judging a sorghum syrup competition in a nearby town. He wanted to see this grass because it was green, lush, and growing well on a sloped hillside during a drought. While visiting the site he was impressed and took seed samples with him. With this seed he conducted variety trials, initiated seed increase nurseries, and lauded its performance. It was released as Kentucky 31 in 1943 and today it dominates grasslands in the humid southeastern US. 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.
Tall fescue is a long-lived perennial bunchgrass species. Photosynthesis occurs throughout the leaves, which form bunches and are thick and wide with prominent veins running the length. The underside of the leaf may be shiny. Emerging leaves are rolled in the bud with no prominent ligule. The auricles are usually blunt but occasionally may be more clawlike. The culm is round in cross-section. Typically, this species of grass has a long growing season and ranges between 2 to tall in seedhead stage..
Tall fescue spreads through seed transmission only - not by stolons or rhizomes, which are common in many grass species. However, tall fescue may have numerous sterile shoots that extend the width of each bunch. There are approximately 227,000 seeds per pound.
Typically found across the southeast US, tall fescue performs best in soils with pH values between 5.5 to 7. Growth may occur year-round if conditions are adequate, but typically growth ceases when soil temperature falls below .
Tall fescue can be found growing in most soils of the southeast including marginal, acidic, and poorly drained soils and in areas of low fertility, and where stresses occur due to drought and overgrazing. These beneficial attributes are now known to be a result of a symbiotic association with the fungus Neotyphodium coenophialum..
This association between tall fescue and the endophyte is a symbiotic relationship since each benefits from the mutualism. The fungus remains completely intercellular, growing between the cells of the aboveground parts of its grass host. The fungus on its own is nonreproductive, although it can be made to reproduce on a Petri plate in culture. It is transmitted to new generations of tall fescue only through seed, a mode known as vertical transmission. In other words, the fungus cannot live on its own, and has an ecological advantage when symbiosis occurs in the grass. The ungerminated seed and fungal symbiont are living organisms and have life spans. The fungus is able to survive in the host for a limited amount of time. Typically, after a year or two of storage the fungal endophyte will die in the seed, and if germinated the stand will be endophyte-free.
When the tall fescue endophyte relationship occurs, it confers a competitive advantage to the plant. Endophyte-infected tall fescue compared to endophyte-free tall fescue deters herbivory by insects and mammals, bestows drought resistance, and disease resistance. In return for shelter, seed transmission, and nutrients the endophyte produces secondary metabolites. These metabolites, namely alkaloids, are responsible for increased plant fitness. Alkaloids in endophytic tall fescue include pyrrolizidines (lolines), ergot alkaloids (clavines, lysergic acids, and derivative alkaloids), and pyrrolopyrazine (peramine).
The lolines are the most abundant alkaloids, with concentrations 1000 higher than those of ergot alkaloids. Neither endophytes grown in culture nor endophyte-free tall fescue produce produce lolines; therefore, the mutualism between the host and endophyte is needed to produce the specific alkaloid. Lolines have been shown to deter insect herbivory, and may cause various other responses in higher organisms. Despite their lower concentrations, ergot alkaloids appear to significantly affect animal growth. Ergots cause changes in normal homeostatic mechanisms in animals that result in toxicity manifested through reduced weight gains, elevated core temperatures, restricted blood flow, reduced milk production and reproductive problems. Peramine, like the ergot alkaloids, is found in much lower concentrations in the host compared with loline alkaloids. Its activity has been shown to be primarily insecticidal, and has not been linked to toxicity in mammals or other herbivores.
Horses are especially prone to reproductive problems associated with tall fescue, often resulting in death of the foal, mare, or both. Horses which are pregnant may be strongly affected by alkaloids produced by the tall fescue symbiont. Broodmares that forage on infected fescue may have prolonged gestation, foaling difficulty, thickened placenta, or impaired lactation. In addition, the foals may be born weakened or dead. 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.