The 2012 ASHS Annual Conference

Four own-root rose cultivars, Carefree Beauty^™ (‘Bucbi’, CB), ‘Frontenac’ (Fr), Polar Joy^™ (‘Baiore’, PJ), and Ramblin’ Red (‘Radramblin’, RR), were planted in a minimal input garden setting and evaluated for landscape performance and drought stress.  Experimental design was a RCB, with one plant of each cultivar per block (n = 4).  Plants were originally planted in winter 2007 and irrigated regularly (approximately once weekly) during growing seasons one and two to ensure establishment.  During years three and four, plants received no supplemental irrigation.  In Summer 2011, northeast Texas experienced exceptional drought and heat. Temperatures exceeded 37.7 °C (100 °F) on 57 days and estimated pan evaporation rates frequently exceeded 10 cm/week.  Landscape performance was rated monthly on a scale of 1 to 10, with 10 being exceptional and in full bloom.  Plants received a drought stress rating using a 0 to 5 scale, with higher values representing increased drought stress symptoms on the foliage, such as wilt, loss of color, leaf scorch, and chlorosis.  Plants were dug at the end of the study to evaluate the roots by carefully digging in a circular pattern, 60 cm from the plant stem.  When individual roots were found, the root was carefully dug beyond the original radius until the entire length was exposed.  CB and PJ had the highest landscape performance ratings.  RR had significantly higher drought stress ratings than other cultivars.  Surprisingly, no correlation was found between any variables of root size and drought stress.  Root dry weight was, however, positively correlated with landscape performance, confirming the importance of root size for landscape performance during periods of extreme drought.