Food Reserve Storage, Low‐Temperate Injury, Winter Survival, and Forage Yields of Timothy in Subarctic Alaska as Related to Latitude‐of‐Origin 1

Timothy( Phleum pratense L.) is a valuable forage grass in cool, humid climates. However, the availability of genetic material within the species from over a broad geographic and latitudinal range, and the generally marginal winterhardiness of the species in Alaska has lent uncertainty to optimum germplasm sources for use in this northernmost state. Five experiments compared cultivars from diverse latitudinal sources for characteristics affecting winter survival and forage production in southcentral Alaska. Cultivars from Norway, Iceland, and Finland were more winter hardy than those from North America. In general, winter survival in Alaska was correlated with latitude of cultivar origin, with northernmost cultivars superior to those of more southern origin. ‘Engmo’, a cuitivar of extreme northern origin (69 to 70°N Lat), was more tolerant of freeze stress, stored higher levels of food reserves, had higher concentration of dry matter in crown tissues, and survived winters at this location (61.6°N Lat) markedly better than ‘Climax’, of intermediate latitudinal origin (ca. 45°N Lat), which in turn surpassed ‘Clair’ in these respects, a cultivar of more southern origin (38 to 39°N Lat). Northern‐adapted cultivars were more dormant in autumn after second forage harvest than mid‐temperate‐adapted cultivars. Timothy cultivars from North America, when well established and not winter‐injured, produced forage yields equivalent to Scandinavian cultivars and other extremely winter‐hardy, non‐timothy grasses, including ‘Polar’ bromegrass (predominantly Bromus inermis Leyss. ✕ B. pumpellianus Scribn.), ‘Garrison’ creeping foxtail( Alopecurus arundinaceus Poir.), ‘Nugget’ Kentucky bluegrass ( Poa pratensis L.), and ‘Arctared’ red fescue ( Festuca rubra L.). After sustaining sub‐lethal winter injury, timothy plants displayed a remarkable ability to recover during the growing season and produce second‐cutting forage yields comparable with hardier cultivars. The proportion of total‐season forage yield produced in the first cutting differed with origin of cultivars in the following ranking: Norway = Iceland = Finland > Sweden > Canada > USA. Snow cover in the field greatly enhanced winter survival of marginally winter‐hardy cultivars. Rhizomatous grass species survived the more stressful winters better than timothy. Apparently the more exposed, superficial position of the overwintering tissues of timothy crowns renders even the most winter‐hardy cultivars more susceptible to winter injury than hardy grasses with subterranean overwintering parts.