It is no coincidence that many plants with gray foliage are from mountains or deserts. Gray foliage is ‘glaucous’, which, like glaucoma, diffuses light. This helps to protect it from desiccation and scald when sunny weather is also hot, windy or arid. The glaucous foliage of Rocky Mountain juniper, Juniperus scopulorum, is what distinguishes it most from related North American junipers.
Garden varieties of Rocky Mountain juniper are even grayer than wild plants. Some are even silvery. Also, they tend to maintain a somewhat symmetrical form. Most are compact, with dense evergreen foliage. Some loosen up with age. All want full sun, and seem to enjoy warmth. They lean away from shade. Color seems to be better if plants get watered occasionally through summer.
‘Skyrocket’ is very narrow while young, like a small silvery Italian cypress that gets only about fifteen feet tall. ‘Blue Arrow’ is similar, and becoming more popular because it is more resistant to disease. ‘Medora’ and ‘Cologreen’ are more bluish green. All get plump with age. ‘Wichita Blue’ and ‘Moonglow’ are more conical. ‘Wichita Blue’ is more bluish. ‘Moonglow’ is more silvery gray.