Sclerochloa dura

Sclerochloa dura is a sturdy annual grass forming low, flat clumps of short stems, some prostrate and some upright. The flat, overlapping leaf blades are a few centimeters long. The inflorescence is a crowded, one-sided series of flattened spikelets, each with (2–)3–4(–7) florets. At the base of the inflorescence, each glume has 3–7 prominent veins. The lemmas at the base of each floret are glabrous with rounded tips.^[3][4]

Sclerochloa dura is sometimes confused with Poa annua, especially in a vegetative state. The two species are more easily distinguished based on floral characteristics.^[5][6][7]

Both species flower in the spring. Sclerochloa dura turns yellow as it ages, making it easy to find at the end of its growing season.

Sclerochloa dura was first described as Cynosurus durus by the Swedish botanist Carl Linnaeus in 1753.^[8] Linnaeus based his diagnosis on a specimen collected in southern Europe.^[9] Over the next 75 years, the species was placed in five different genera:^{[10][11][12][1][13]}

In 1812, the French botanist Palisot de Beauvois placed the species in a new genus Sclerochloa,^[14] which means "hard grass", a reference to the leathery glumes and lemmas of its inflorescence.^[15] As of September 2026^[update], the name Sclerochloa dura (L.) P.Beauv. is widely accepted.^{[2][16][17][3]}

Sclerochloa dura is native to northwest Africa, south-central Europe, and central Asia.^[2] It was introduced in North America, South America, and Australia. In North America, it occurs in both Canada and the United States.^[18]

• Canada: British Columbia, Ontario
• United States: Arizona, Arkansas, California, Colorado, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Michigan, Mississippi, Missouri, Montana, Nebraska, New Mexico, New York, Ohio, Oklahoma, Oregon, Tennessee, Texas, Utah, Virginia, Washington, West Virginia, Wisconsin

In the US, it was first discovered near a woolen mill in Yonkers, New York in 1895, after which the species was not seen in New York for over a century. In 1991 it was reported to occur in a total of 18 US states;^[19] however, only a single population was known in 10 of those 18 states. Between 1995 and 2002, at least 162 additional sites were documented from Illinois, Indiana, Michigan, New York, Ohio, Ontario, Pennsylvania, West Virginia, and Wisconsin. Most of these new populations were found on fairgrounds, hence the common name "fairgrounds grass".^[20] Besides fairgrounds, it is found in lawns, campsites, roadsides, and especially athletic fields. It prefers severely compacted soils at heavily disturbed sites.^[3]