Morphology, Turf Quality, and Heat Tolerance of Intermediate Ryegrass

Bermudagrass ( Cynodon spp.) turf is often overseeded with a cool-season species such as perennial ryegrass ( Lolium perenne L.) to provide an improved winter surface for activities such as golf or athletic events. Perennial ryegrass can become a persistent weed in overseeded turf due to the heat and disease tolerance of improved cultivars. Intermediate ryegrass is a relatively new turfgrass that is a hybrid between perennial and annual ryegrass ( L. multiflorum Lam.). Very little information is available on intermediate ryegrass as an overseeding turf. Greenhouse, field, and growth chamber studies were designed to compare two cultivars of intermediate ryegrass (`Transist' and `Froghair') with three cultivars of perennial ryegrass (`Jiffie', `Racer', and `Calypso II') and two cultivars of annual ryegrass (`Gulf' and `TAM-90'). In a greenhouse study, the perennial ryegrass cultivars had finer leaf texture (2.9-3.2 mm), shorter collar height (24.7-57.0 mm), and lower weight/tiller (29-39 mg) than the intermediate and annual cultivars. In the field studies, the intermediate cultivar Transist exhibited improved turfgrass quality (6.1-7.1) over the annual cultivars (4.5-5.8) and the other intermediate cultivar Froghair (5.4-5.7). However, neither of the intermediate cultivars had quality equal to the perennial ryegrass cultivars (7.0-7.9). The perennial ryegrass cultivars exhibited slow transition back to the bermudagrass compared to the annual and intermediate ryegrass cultivars. In the growth chamber study, the annual and intermediate cultivars all showed increased high-temperature stress under increasing temperatures compared to the perennial cultivars, which did not show stress until air temperature exceeded 40 °C. Collectively, these studies indicate that the intermediate ryegrass cultivar Transist may have promise as an overseeding turfgrass due to its improved quality compared to annual types and a lack of heat tolerance relative to perennial cultivars, but with transition qualities similar to perennial ryegrass.