Dactylis glomerata L.

Abstract

Cocksfoot or orchard grass is common in Europe within the area of the July isotherms 50[degree]-80[degree]F. In the United Kingdom it rarely grows at higher altitude than 609 m, but in Kashmir and Western Tibet has been found up to 3656 m. Plants show great variation in growth form and size. Domin gives 160 named infra-specific varieties while Hubbard states that the number in European literature is at least 200. Plants tend to be solitary, panicle shoots are from 30-160 cm tall; anthesis, which is optimum in June, occurs during the early morning. The pollen is carried by wind so that outcrossing is usual and prolific seed production is possible. Self-compatibility is very low as a rule. The viability of caryopses kept dry in the laboratory remained high over 4 years then fell away rapidly, and almost to zero in 12 years. The germination of new seed in official tests reached 90% or slightly more, but sown in soil in boxes under greenhouse conditions the viability was about 10% lower, and showed greater year to year variation. Buried caryopses may retain viability if they remain in the upper 2-3 inches, but apparently relatively few do so. D. glomerata is tetraploid, 2n = 28, but aneuploids of 26, 27, 29 and 30 are found. Some tetraploids carry B-chromosomes. Until recently only 1 species was known, but now a diplpid D. polygama Horvats (D. aschersoniana Graebn.) has been recorded. Artificial hybrids from D. glomerata X D. polygama were triploid and male sterile. The parasites and diseases of D. glomerata in the United Kingdom are listed.