Rocky Mountain juniper 'Blue Heaven' makes a beautiful accent plant.
Rocky Mountain juniper is an evergreen large shrub or small tree to 50 ft (15.2 m) tall, but usually much smaller. Specimens are variable in habit, sometimes squat and shrubby, but usually narrowly cone shaped. The trunk is short and stout, often dividing near the ground. The branches are rather thick and spreading to partly erect. Rocky Mountain juniper has reddish bark that is stringy in narrow strips but does not exfoliate. Most of the leaves are like overlapping scales, closely pressed to the twigs. Juvenile leaves, usually only found on young seedlings, are more like needles, and they spread away from the twigs. The foliage is dense and pleasantly aromatic. Trees may have male or female cones, but not both. The fruits are fleshy berrylike spherical cones, about 1/3 in (0.8 cm) in diameter. They are bright blue with a whitish bloom and sweet tasting, with thin skins. Rocky Mountain juniper is closely related and quite similar to eastern redcedar, and was once believed to be the same species. But eastern redcedar has fruits that mature in a single season, whereas those of Rocky Mountain juniper take two year to ripen. Also, eastern redcedar had exfoliating bark. The two species hybridize where their ranges overlap.
Rocky Mountain juniper has dozens of named cultivars. 'Blue Heaven' is a shrub to 6 ft (1.8 m) tall with a conical habit and strikingly blue green foliage. 'Sky Rocket' is very narrow, almost pencil shaped and has grayish foliage; it is so skinny that it borders on the weird. 'Gray Gleam' has gray blue foliage which becomes more silvery in winter; it gets 10-15 ft (3.1-4.6 m) tall and has a dense, pyramidal habit. 'Table Top' is a wide spreading shrub to 6 ft (1.8 m) tall and 15 ft (4.6 m) wide with bluish foliage. 'Tolleson's Blue Weeping' gets 20 ft (6.1 m) tall and 10 ft (3.1 m) wide with arching branches and pendent, ropelike silvery green foliage.
Rocky Mountain juniper occurs in isolated and scattered localities within a wide band from British Columbia to North Dakota, and south to Arizona and New Mexico. It grows from near sea level in the northern part of its range to more than 8000 ft (2438 m) above sea level in the south. Rocky Mountain juniper grows in alkaline soils on ridges, cliffs and rocky slopes, sometimes in pure stands, but more often in association with other mountain loving evergreens such as ponderosa pine, pinyon pine and Douglas-fir.
Rocky Mountain juniper is a slow growing tree that adds only 6-12 in (15.2-30.5 cm) per year, but one that can live more than 300 years. In cultivation it tolerates acidic to alkaline soils, and does best in those that are loose and well drained. It is best adapted to culture in western and northern North America. Light: Seedlings and saplings can tolerate rather dense shade, but Rocky Mountain junipers, even the smaller cultivars, need full sun to grow to their full potentials. Moisture: Rocky Mountain juniper is tolerant of drought, but perhaps less so than the other junipers. It should be watered before the soil becomes completely dry. This juniper does poorly in humid climates, but does fine in hot, dry climates. Hardiness: USDA Zones 4 - 7. Propagation: The junipers are difficult to propagate from seed. Most cultivars are started from cuttings of ripe wood in autumn, rooted in a cold frame; or soft wood cuttings in summer, rooted with bottom heat and under mist. Some are grafted onto seedlings.
Use any of the cultivars of Rocky Mountain juniper for attractive foliage effects in all seasons. This evergreen is useful as a screen, hedge or foundation plant. They make great anchors or focal points for the ends of hedges or mixed borders. Rocky Mountain juniper is a tidy, formal accent shrub alone or in small groups.
Although most cultivars are probably too formal for naturalistic gardens, Rocky Mountain juniper is ideal for neat, well-organized landscapes. Most cultivars require little or no pruning and are relatively free of cultural problems, insects and diseases. They tolerate heat and drought well.