- Small, evergreen tree or shrub
- Mostly ascending branches
- Pollen and berry-like seed cones at branch tips on separate plants
- Bluish-purple berries covered with a waxy, whitish bloom
- Leaves on mature plants are opposite and scale-like
- Leaves on young plants are prickly, needle-like, and in whorls of 3
- Thin, fibrous, shredded bark
- Coniferous shrubs or trees often with fibrous bark on mature trunks
- Scale-like leaves or needles; plants often have both forms
- Separate male and female cones on branch tips of the same tree or separate trees
- Each cone has 2 seeds (sometimes 5–6)
- Many members of this family have aromatic and highly valued wood
Small, erect evergreen tree or shrub, up to 10 m tall, with a conical form or a wide, irregularly rounded crown. Occasionally grows as a sprawling shrub, less than 1 m tall.
Usually with a single trunk that is often twisted and knotty. Dense growth of mostly ascending branches that often grows close to the ground. Leaves of mature trees arrange in opposite pairs, cover the branch in 4 vertical rows, and make the stem appear 4-angled. These leaves are grayish-green and scale-like, 1–1.5 mm long, lying flat and tightly encasing the branches, barely overlapping. Leaves on seedlings and young trees are needle-like, longer than on old trees, 5-7 mm long, and prickly. The juvenile leaves arrange in whorls of 3 on branches.
Thin, grey or reddish-brown bark that shreds off in strips. Bark on mature trees is fibrous or stringy with narrow ridges of scales. Aromatic wood with creamy white sapwood and reddish heartwood.
Pollen (male) and seed (female) cones on separate plants and attach at branch tips. Fleshy round, bluish-purple to bluish-black, berry-like seed cones, 5–6 mm long, have vestiges of fused cone scales visible on their surfaces. Seed cones are dry and resinous with a heavy, waxy bloom and mature during the second summer, producing 1–5 wingless seeds. Pollen cones are egg-shaped, 3–5 mm long, brown and less conspicuous with 12–16 stamens (pollen organs).
Dry, open, rocky or sandy soils of grassy slopes, open shrub lands and forests, rock outcrops, and old river terraces at low- to mid-elevations. Often growing in calcium-rich, nitrogen-deficient, or alkaline soils and on warm, dry, south facing slopes. Does not tolerate much shade.
The dry habitats, their thin bark, and the low, resinous, flammable branches of Rocky Mountain juniper leave them relatively defenseless against fire. Therefore, they prefer to germinate in areas with little to no neighboring vegetation to spread fire to them. Fire suppression has enabled Rocky Mountain junipers to spread beyond the sites with rocky or marginal soils to which they were previously relegated. Larger Rocky Mountain junipers can survive some low fires as their own shade and litter create a firebreak, and inhibit germination of other plants after these fires. Rocky Mountain junipers typically live for 200–300 years, but specimens over 1,000 years old have been found.
The species name scopulorum “broomy,” which refers to the dense growth of branches. Several species of birds, such as Townsend’s solitaires (Myadestes townsendi) and waxwings (Bombycillidae spp.), and some mammals, including bighorn sheep (Ovis canadensis), eat the berries (seed cones). The passing of berries through these animals’ digestive tracts dissolves the fleshy coating and enables germination of the seeds. The berries cling to trees all winter and can persist for many years, making an excellent year-round food source. Deer (Cervidae spp.) and livestock graze the foliage and appear to have favorite trees that they graze more heavily than others. These trees often have a mushroom-shaped growth form with shortened branches up the height of the browse line.
The raw berries are edible and sweetest after the fall of their second year. Small quantities of berries are used to flavor stew, meat, and vegetable dishes such as sauerkraut and potato salad. Some tribes cooked, mashed, and dried Rocky Mountain juniper berries into cakes for winter use. The berries can also be roasted, ground, and brewed as a coffee substitute. The most well known use of Rocky Mountain juniper berries and other species of juniper is for flavoring gin.
The berries are widely used medicinally but may irritate the kidneys with prolonged use. Eating a few berries before meals stimulates digestive acids. A tea made of the berries alleviates gas, coughs and stomach ailments, and can serve as a diuretic to disinfect the urinary tract and help dissolve kidney stones. The Blackfoot people used a juniper tea to cure vomiting. An infusion made of the berries and leaves can be added to baths to stimulate rheumatism, or used as an antiseptic wash and an anti-dandruff hair rinse. Herbalists during the Middle Ages also harnessed the disinfectant properties by keeping juniper berries in their mouth as an antiseptic barrier while treating people with contagious diseases. Some tribes also burnt or boiled the boughs to disinfect rooms, ward off illness, and repel insects.
The wood is prized for fence posts due to its ability to avoid decay for a long time. The tough sapwood has also been used for making bows, spear handles, clubs, and spoons. The fragrant wood chips and boughs impart a nice flavor to smoked fish and meat. The fibrous bark provides good tinder for starting fires.