The Effect of Rose Root Size on Drought Stress Tolerance and Landscape Plant Performance

Abstract

Four rose (Rosa hybrida) cultivars, Carefree Beauty^™ (‘BUCbi’, CB), ‘Frontenac,’ (Fr), Polar Joy^™ (‘BAIjoy’, PJ), and Ramblin’ Red^™ (‘RADramblin’, RR), were evaluated for landscape performance and drought stress. Plants were planted in an RCB design, with four blocks, during winter 2007 and irrigated regularly during growing seasons one and two. During years three and four, plants received no supplemental irrigation. In summer 2011, temperatures exceeded 37.7 °C (100 °F) for 65 days and pan evaporation rates exceeded 70 mm·wk^-1. Landscape performance was rated monthly on a scale of 0 to 10, with 10 being exceptional. Plants were rated for drought stress using a 0 to 5 scale, with higher values representing increased drought stress. Plant roots were harvested by digging in a circular pattern 60 cm from the plant stem. Individual roots were carefully dug beyond the original radius until the entire length was exposed. CB and PJ had the highest landscape performance ratings, while RR had the highest drought stress scores. Though RR and Fr were similar in height, width, and shoot dry weight, PJ and CB had higher root dry weights. Strong correlations were found between landscape performance and root dry weight and root fibrosity. Drought stress was strongly correlated with root mass.