Plant 339

Lolium perenne L. (Poaceae)

Perennial ryegrass

Perennial ryegrass is native to Eurasia and North Africa but has been introduced to temperate and high-elevation tropical regions around the world as a forage and amenity grass. In Britain, perennial ryegrass is the most frequently sown and economically important forage grass. Moreover, it was the first grass sown for agricultural purposes, with records of its cultivation dating to the late sixteenth century. This highly variable, wind-pollinated species is especially abundant on damp, fertile soils.

Forage is essential for feeding livestock. Forage quality is determined by its nutrient content, the amount of energy grazers gain from it (digestibility) and the chemicals produced when it is digested. Forage nutrients include minerals, structural (cell-wall) and non-structural (starch, sugars, organic acids) carbohydrates, proteins, and fats. However, grasses are seasonal in their growth patterns. In Britain, when temperatures fall below five degrees Celsius, grasses hardly grow at all but grow vigorously in warm, wet periods.

As grasses get older the amount of stem relative the amount of leaf increases and overall forage quality decreases. Consequently, grasslands managed for grazers must use methods to promote the production of leaves over stems by changing either management regimes or the genetics of the fodder crop. Moreover, if livestock is to be fed over the lean months, forage grasses must be capable of being stored either dry as hay or pickled as silage; harvest happening when nutritional quality is at its maximum.

In 1681, the agriculturalist John Worlidge could hardly contain his enthusiasm for ryegrass, as it can ‘improve any cold, sour, clay, weeping lands, for which it is best, but good also for drier uplands, especially stony, light, or sandy lands’. In 1826, in Hortus Gramineus Woburnensis, George Sinclair described the results of experiments on field management and the improvement the nutritional quality of perennial ryegrass. Dramatic changes in the forage fortunes of perennial ryegrass came in the early twentieth century, when artificial fertilisers were applied to fields and its genetics manipulated.

Under the direction of the forage grass breeder George Stapledon, scientists at the Welsh Plant Breeding Institute selected strains of perennial ryegrass, adapted to many different climatic conditions and management regimes, from across its geographical and ecological range. The team selected varieties of perennial ryegrass with tolerance of trampling, and regular mowing and heavy grazing. Today, there are dozens of perennial ryegrass varieties, often with highly specialised features for use as forage or amenity grasses.

Further reading

Beddows, AR 1967. Biological Flora of the British Isles. Lolium perenne L. Journal of Ecology 55: 567-587.

Harvey G. 2002. The forgiveness of nature. The story of grass. Vintage.

Stephen Harris