How to Plant, Grow, and Care for Rocky Mountain Juniper

Few trees work well in both wild landscapes and home yards! Rocky Mountain juniper is the exception. It’s tough and resilient, yet it’s also decorative and gorgeous. Its scaly leaves, brown-red bark, and blue berries make a statement in the front yard.

Not only is this juniper a great low-maintenance choice for the gardener, but it’s also a superb tree for wildlife. It provides habitat space for roaming mammals and insects, and it feeds hungry birds with its berries and seeds. 

When choosing junipers for the landscape, it’s best to select a species that originates from nearby. The Rocky Mountain juniper is a great choice for dry gardens in the western U.S. Consider alternative junipers if you live in states with high humidity levels and wet soils.

What Is It?

Rocky Mountain juniper is a long-lived evergreen tree that slowly grows taller and wider as it matures. It’s an iconic native species that grows well without extra care, irrigation, or pruning. Though it is low-maintenance, it prefers to grow in high elevations near mountainous regions. 

Native Area

Rocky Mountain junipers are native to British Columbia and Alberta, the western U.S., and northern Mexico. As their name suggests, they fill high-elevation areas throughout the Rocky Mountains. They love gritty, gravelly soils that drain freely.

This juniper’s range overlaps with the western and common junipers, Juniperus occidentalis and J. communis. It resembles the western juniper, as both have blue berries, scaly foliage, and brown-red bark. In its native range, it tolerates salt spray, dry weather, and air pollution. 

Characteristics

This native tree of the Rockies has a few distinguishing characteristics. You can tell it apart from others by its height, stature, and growing habits. This species reaches between 30 and 40 feet tall in maturity, with a narrow to medium-sized spread. 

Trees in the sun grow into pyramidal, triangular shapes that are incredibly ornamental and highly desirable. They tend to have a single trunk. The more shade the trees receive, the less pyramidal they’ll grow. Shaded junipers grow long sprays with thin branches, and they tend to form multi-trunk trees.

Off the branches sprout small, male cones in spring that dump pollen onto receptive female cones. The fertilized cones morph into blue berries during the growing season. They are technically soft cones, not berries, despite their look. As the false berries fall to the ground, the seeds inside may sprout into new juniper seedlings.

Planting

Whether you’re buying trees from a nursery or planting seeds yourself, the planting process is an important step for the future health of your Rocky Mountain junipers. Give your junipers what they need and they’ll reward you with lush growth, ridged bark, and beautiful blue berries.

Growing from Seed

Though it’s a challenging process, it’s not impossible to grow a juniper crop from seeds. Start by finding a reputable source for seeds. Gather them yourself from nearby specimens, or look online for a specialty retailer. They’re commonly available in the West, where the species naturally grows. 

Juniper seeds won’t germinate in their first year. They follow a natural process that allows them to sprout the following spring. They typically stay on the tree and fall off in the second spring, after which they readily germinate in the soil.

You have two options here. Collect juniper berries that have sat on the tree for a year already, or collect fresh ones. It’s easier to sow one-year-old seeds than fresh ones. Plant the one-year-old seeds in pots or the ground, water them well, and wait for them to sprout.

If you’re sowing fresh juniper seeds, you’ll want to plant them outdoors this spring. Keep them moist, not soggy, and let them overwinter outdoors. You’ll see seedlings sprout the following spring as days lengthen and warm after winter. 

Transplanting

Transplanting is a straightforward process if you have the right tools. Gather a spade or shovel and some mulch. Compost is a great mulch to use, though leaf mold, straw, or fallen leaves work well too. If you’d like to stake your tree, also prepare stakes or supports and place them nearby. 

Start the process by preparing a hole for planting. Choose an open site with full sun or partial shade, and avoid planting it near other large trees and shrubs. Using your shovel or spade, dig a hole as deep and twice as wide as the rootball. 

Place your tree’s rootball inside the hole, and add stakes now if you plan on staking your Rocky Mountain juniper. Backfill the hole with the garden’s native soil until it reaches ground level. Water the tree well, then add more soil if the ground sinks low. 

Then, add a mulch, like compost, on top of the soil. Place a layer two to three inches thick, and leave some space between the trunk and the mulch. The compost will feed, insulate, and protect your juniper’s roots while they establish in the planting hole. 

How to Grow

Give a Rocky Mountain juniper what it needs, and it’ll ask for little else! It may need some care in its first year, though it’ll be hardy and drought-tolerant in the years thereafter. Give your juniper lots of sun, well-drained soil, and regular airflow to help it survive and thrive in the landscape. 

Light

These mountain dwellers prefer full sun or partial shade to grow well. How much light they receive influences their mature size and shape. Those growing under full sun will be broad and pyramidal, while those in partial shade will have many trunks with slightly weeping branches. 

Too much shade is detrimental to junipers. Avoid growing this tree in sites with fewer than three to four hours of daily direct sunlight. The more sun the juniper receives, the better it will grow. You want to emulate their native range on mountainsides, where they’re exposed to many hours of piercing sunlight. 

Water

Rocky Mountain junipers don’t need that much water to survive. They’ll struggle in wet sites, as they prefer a dry soil culture. You may not need to water them at all during the growing season! They’ll grow in moist or dry conditions with little to no extra irrigation.

Some winter moisture is common where these trees grow. They tolerate some winter rain and snow, though they struggle with ice. Their branches will break under the weight and pressure of large amounts of ice. 

Soil

Well-drained soil is the best type for this species. It tolerates a wide range of soils, as long as they’re free-draining. Sandy, dry soils are ideal, though junipers adapt well to a wide range of garden soils.

If you notice signs of pooling or sogginess in the ground, consider transplanting the Rocky Mountain juniper to a new, dry location. Sogginess is a leading killer of these mountain-dwelling junipers. 

Fertilizing

You don’t need to fertilize this juniper species if it’s growing in the ground. In-ground specimens rarely need extra nutrients, and they thrive in poor soils. 

Potted juniper trees are a different story. They may need some fertilizer during the growing season to continue growing well. Apply a regular dose of well-balanced organic fertilizer once in the spring as new growth sprouts. 

Maintenance

These juniper trees require little maintenance to thrive. They’ll retain their lower branches if you let them! For a typical tree shape, you may want to prune these lower branches off when they’re young. This frees up the lower portions of the trunk.

Aside from pruning the lower branches, you may need to remove dead or damaged limbs after winter. Winter storms can cause damage, and removing the damaged parts will make room for fresh new growth. 

Propagation

There are two main means for propagating Rocky Mountain junipers: taking cuttings and sowing seeds. Cuttings replicate the original plant to make new clones. Seeds are slow to grow, but planting them is a fun way to find new, disease-resistant varieties. 

Take Cuttings

Take cuttings from healthy branches during the growing season. Select four to six-inch portions and prune them off the main limbs. Strip the cuttings of their lower leaves, then place them in pots with fresh potting soil. 

Juniper cuttings take weeks to months to sprout roots. Keep them under dappled sunlight or partial shade while they root, and ensure their soil stays moist, but not soggy. 

Test the cuttings by lightly tugging them. If they resist, they likely have roots forming under the soil. Let them grow new shoots and roots until they’re robust and ready for planting. Then, transplant them in the spring or fall. 

Save Seeds

Juniper seeds reside inside berry-like cones. To save them, you’ll need to extract them from the berries and store them in a cool, dark, and dry location. Start by sourcing blue berries from a local Rocky Mountain juniper, or find them available online. 

Unlike other seeds that are easy to collect, juniper seeds are difficult to process. You’ll need to separate the seeds from the berries with a blender! Put the berries inside the blender with lots of warm water, then pulse them on a low speed. After pulsing, remove the floating debris and strain the seeds that sink to the bottom.

The seeds may still be sticky with resin after the first blending period. To clean them, pulse them again with plenty of warm water and a few drops of detergent. Strain the seeds again, then let them dry on a paper towel or cloth rag.

Store the dry seeds in a container, then put the container in a cool, dark, and dry location. Pantries, closets, and fridges work well. 

Popular Varieties

Rocky Mountain juniper is one of the more widely used trees of the genus. Plant breeders and collectors have discovered dozens of varieties with various habits. Find cultivars that perform as shrubs, trees, or even as groundcovers! The possibilities are endless. 

Blue Arrow

‘Blue Arrow’ is a narrow, columnar cultivar that tops out at between 12 and 15 feet. It’s perfect for tight spaces or for making a living wall to separate property lines. This variety also grows well in containers. Plant two on opposite sides of a walkway for a dramatic effect.

Alongside its columnar habit, ‘Blue Arrow’ features blue-green foliage that’s striking in gardens. Pair it with green plants to make it stand out, or grow it with other bluish trees like the Colorado blue spruce. 

Moonglow

‘Moonglow’ is another upright cultivar that’s less narrow than ‘Blue Arrow’. It features sweeping branches and a columnar, pyramidal shape. The scaly, evergreen foliage has a silver-blue hue that shines under direct sunlight. 

‘Moonglow’ works well as a specimen in the landscape. Plant it in a main focal point of the yard with a tree well, then grow shade-tolerant perennials beneath its branches. 

Wichita Blue

If you like the dwarf Alberta spruce, you’ll love the ‘Wichita Blue’ juniper. It grows into a compact, conical shape. It features whitish, blue-silver leaves that form upright sprays. 

‘Wichita Blue’ tends to stay between 10 and 15 feet tall, though it can grow up to 30 feet when mature. Give it plenty of room to grow, or selectively prune it to keep it small. 

Common Problems

These trees tend not to have major issues with pests and diseases, though you may see some spotty leaves or feeding insects while they grow. Use a three-step approach to combat pests: monitor, prevent, and intervene. 

Pests

You may see aphids, scale, webworms, bagworms, spider mites, and wood borers on your tree. The best way to prevent them is to maintain a healthy tree. Add mulch to the soil a few times a year to feed the soil, and avoid overwatering your Rocky Mountain juniper. 

If pests do occur, try spraying them off with a hose daily until they disappear. The best way to battle a pest is to target it specifically. First, identify the pest, then find potential treatments and prevention methods to battle the pesky creatures. 

Diseases

You may see signs of twig blight and cedar-apple rust on your juniper. Twig blight causes stem dieback, while cedar-apple rust grows alien-like orange structures on infected branches. Prune affected branches, and monitor to ensure the disease hasn’t spread elsewhere.