The 2011 ASHS Annual Conference

Water shortage and poor water quality are critical challenges to gardening and landscaping in many regions of the world. Therefore, selection of drought and salt tolerant plants becomes increasingly more important for the development of sustainable landscapes. Earth-Kind^® is a special designation given to select rose cultivars by the Texas AgriLife Extension Service through the Earth-Kind landscaping program. It is based on the results of extensive research and field trials and is awarded only to those roses demonstrating superior pest tolerance combined with outstanding landscape performance. Knowing how Earth-Kind^® rose respond to drought stress will provide useful information that breeders can use in developing adaptable rose cultivars and lead to a better understanding why certain cultivars withstand unfavorable environmental conditions. A greenhouse study was conducted to evaluate four Earth-Kind^®- rose cultivars (‘RADrazz’, ‘Belinda’s Dream’, ‘Old Blush’, and ‘Maria Pavie’) in response to drought stress. Plants grown in 11.4-L containers with a peat-based substrate were subjected to two watering treatments, well watered (35% average soil moisture content) and cyclic drought stress. The cyclic drought stress was induced by watering the plants to container capacity and then withholding irrigation until container weight reached a predetermined weight and plants exhibited incipient wilting. At each watering time, plants were well irrigated using a nutrient solution containing 300 mg∙L^-1 15-5-15 Cal Mag fertilizer and reverse osmosis (RO) water. Shoot growth and flower number were reduced in the drought treatment compared to the well-watered control in all cultivars. Net photosynthetic rate (P_n), stomatal conductance (g_s), transpiration rate (E), and mid-day water potential of all cultivars decreased as substrate moisture content decreased. However, the relationship between these physiological parameters and the substrate moisture contents differed among the cultivars, and ‘RADrazz’ was considered to be more tolerant to drought compared to the other three cultivars.