How to Grow and Care for Rocky Mountain Juniper Trees

Rocky mountain juniper tree with blue-green leaves in front of pink flower bush

The Spruce / Evgeniya Vlasova

“Of the mountain” is the meaning of the botanical name for Juniperus scopulorum. Its normal form is unlike other junipers in that it is somewhat formal in shape. It reaches mature heights of 30 to 40 feet in a columnar shape with one or two main leaders or main “stems”. The foliage depends on the variety but ranges from dark green to blue-green. The needles on young plants are soft and short but become appressed and scale-like as the tree matures. Another shining feature is the rocky mountain juniper’s berry-like cone. The little fleshy cones ripen in their second year, are dark blue, covered in a whitish bloom, and have been used for food, medicine, and making all types of beverages from tea to gin.  

Botanical Name Juniperus scopulorum
Common Name  Rocky Mountain Juniper, Red Cedar
Family Cupressaceae
Plant Type Tree, shrub 
Mature Size 3 to 30 ft. tall, spread of 3-15 ft.
Sun Exposure Full, Partial
Soil Type Sandy
Soil pH Neutral
Hardiness Zones 4, 5, 6, 7, 8, 9
Native Range North America

Rocky Mountain Juniper Care

A rocky mountain juniper is a very adaptable tree, accepting of a variety of soil types. Though it loves full sun, it can also withstand very cold temperatures, making it the perfect tree for northern zones. It's a drought-resistant variety, so it can handle long summers with little rain. It's hardy enough that fertilizing isn't necessary, and if you happen to forget to water it, the tree will forgive you. This tree is so adaptable that it can be used as a bonsai alternative, as a windbreak, or as a towering tree in a vast landscape.

Rocky mountain juniper tree with blue-green leaves foliage closeup

The Spruce / Evgeniya Vlasova

Rocky mountain juniper tree stem with blue-green scale-like foliage closeup

The Spruce / Evgeniya Vlasova

Light

The rocky mountain juniper prefers full sun but will take to partial shade. Like all junipers, it is pretty adaptable.

Soil

The ideal soil for this tree is a loose, inorganic mix of a neutral pH. Adding vermiculite, perlite or a pumice mixture is perfect if you are looking to amend your soil to give it texture to help your juniper.

Water

The tree does not require much watering and is very drought tolerant. This plant is perfect for xeriscaping or other waterwise gardens.

Temperature and Humidity

This plant prefers warm dry temperatures, but it is cold hardy to -35 degrees Fahrenheit. 

Fertilizer

The rocky mountain juniper does not require feeding.

Types of Rocky Mountain Juniper

In the United States, the rocky mountain juniper is a favorite for the bonsai enthusiast. To create a bonsai using a rocky mountain juniper, there are many dwarf or miniature cultivars available that are perfectly suited for bonsai creations.

Juniperus scopulorum ‘Snow Flurries’ is an especially nice, variegated cultivar. You need to transplant it into a pot just large enough for its roots with a premixed bonsai soil that will consist of inorganics such as pumice, vermiculite, and crushed lava. Occasionally, pine bark is also included. 

Once established for a few years, you can re-pot to a larger pot by removing the soil from the roots and trimming and shaping the tree into your own unique work of art. 

If you are looking for a tall slender cultivar for the garden, you might want to choose Juniperus scopulorum ‘Blue Arrow’, this cultivar is often used as windscreens and hedges. 

Pruning

Rocky mountain juniper should be pruned around a central leader, a hardy stem that grows upright. Prune it in early spring, after the last chance of frost has passed but before new buds set on the stems. Cut any dead, damaged, or diseased stems down to the trunk. Cut out tips of branches if it might open up the tree and allow light to touch more branches in the center. In total, try to cut back only 20 percent of the tree each season.

Propagating Rocky Mountain Juniper

Juniper can be propagated via cuttings, seed, or grafting. Grafting is rather difficult and requires an experienced gardener to make it work well. Therefore, creating a cutting for propagation, or using seeds, will be the most common routes for the typical home gardener.

To create the proper cutting, choose a branch that is healthy and green. Do this during the winter or early spring, as you want to use only established growth. Separate the cutting from the main branch with sharp shears, so that you have a "heel" or "node" on one side and lively growth on the other.

Peel the bottom half of the cutting, up to about 1 inch, then dip it in rooting hormone. Place this in damp peat moss and tamp the medium down thoroughly. Use pots that are at least 5 inches deep to allow for better root growth. It might take up to six months for the cuttings to develop their root systems.

How to Grow Rocky Mountain Juniper From Seed

Collect seeds in the fall, clean them well, and place them in a paper bag. Keep this bag in a cool place, such as a garage, through the winter. In early spring, sow the seeds in 5-inch pots, with about 1 inch between each seed. Cover them lightly with potting soil and water thoroughly. Though a greenhouse is best for growing these tiny saplings, a transparent lid can help raise the humidity enough if the pots are in sunlight. Look for temperatures above 75 degrees Fahrenheit and humidity at above 75 percent. Expect the first shoots to appear within two weeks.

Potting and Repotting Rocky Mountain Juniper

Rocky mountain juniper can't be grown in pots unless it is a variety specifically meant for bonsai enthusiasts. Allow other varieties to grow in a pot only until ready to plant outdoors.

To plant your tree, pick your location knowing the size, and the characteristics of your tree. Consider the utilities and any infrastructure under the plant and think about future improvements.

Once a site is chosen, dig a hole twice as wide as your tree’s root ball, or container, and just as deep. Remove the tree from the container or burlap and set it in the hole. Maintain it in an upright position as you fill the hole and compress the soil. Lightly mulch to a depth of 3 inches to the dripline of the tree making sure that no mulch touches the trunk of the tree itself. 

If your tree is in a windy spot, consider staking it to ensure that it remains upright.

Overwintering

These trees thrive in even very low temperatures. Young, immature trees might benefit from mulch over the roots if the temperatures dip below 10 degrees Fahrenheit. Adult trees are cold hardy and don't need protection through the winter.

Common Pests and Plant Diseases

Spider mites and bagworms are common pests that make their home in the rocky mountain juniper. Botanical oils and insecticidal soaps can help with the problem. Bagworms can be removed by hand and killed by dropping into a bucket of warm, soapy water.

Rocky mountain juniper is vulnerable to Cercospera blight; copper-based fungicides can help with this issue. The tree might also develop Botryospaeria stevensii canker, especially when growing in humid areas. Cutting out the affected area is usually the best and easiest solution. Keep in mind that canker usually takes hold only if the tree is already stressed, so pay closer attention to proper watering, pruning, and soil amendments.

FAQ
  • How long can Rocky Mountain Juniper live?

    One especially old specimen, the Jardine Juniper, was discovered in 1923 within the Cache National Forest. This ancient tree has been dated to be approximately 1500 years old. Proper planning needs to be done when planting this tree, as it is going to be around for a long while.  

  • Can Rocky Mountain Juniper grow indoors?

    The dwarf variety can be trained much like a bonsai plant. These are designed to grow indoors. Other varieties must be planted outdoors as soon as their root system is mature enough to dig into the ground.

  • What trees are similar to Rocky Mountain Juniper?

    Some trees, like the Utah Juniper, as so similar to the Rocky Mountain Juniper that it can be tough to tell them apart. The Welch Juniper and Winter Blue Juniper can look similar, though have different colorations.