Answer: Newly planted trees and shrubs will need regular watering for their first year, until the roots become established. Your best bet might be to plant in early fall when natural rainfall is abundant, which should give the plants a jump start on root establishment prior to the hot, dry conditions of summer. Neither rhododendron or azalea will be happy in the severe weather of your mountain garden. Sorry!
Shrubs that will grow well under the conditions you describe include Ceanothus (wild lilac), Cercis occidentalis (western redbud), Cerocarpus (mountain mahogany), Cordia, Dodonaea viscosa (hop bush), Dendromecon (bush poppy), Fremontodendron (flannel bush), Genista (broom), Lavender, Juniperus, and Grevillea.
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