The 2012 ASHS Annual Conference

Winter-hardiness is an important agronomic trait for perennial horticultural crops such as rosemary (Rosmarinus officinalis L.). For many species winter-hardiness is reported as an average, without taking into account genetic variation within the species. A randomized, replicated winter hardiness field study was conducted at the NMSU Agricultural Science Center near Artesia, New Mexico during the winter of 2010–11 with 89 genetically distinct clonal lines of rosemary. The study showed extremes of variation in winter hardiness from total plant loss to minimal damage. Several clonal lines with an ability to withstand freezing temperatures (as low as –21 °C) were identified. Winter survival ranged from 0% to 100% in the collection of lines studied. Winter hardiness could be classified into (a) absolute leaf tissue survival; and (b) regrowth ability. Absolute leaf tissue survival was limited to only a few clonal lines. In contrast, regrowth from the base was apparent on several lines that appeared to be dead in early March. The clonal line known as “White Flowered” exhibited the best winter hardiness and optimal phenotype with limited injury and rapid spring regrowth.