Introduction

Juniperus scopulorum is a native plant that can be found in the western United States. In general, Juniperus scopulorum is a slow growing evergreen tree with a narrow, pyramidal habit that grows to a mature height of 30 to 40 feet. It is similar to other junipers in that it requires a full sun exposure and will tolerate dry and droughty soils. Juniperus scopulorum is useful as a privacy screen or specimen. This juniper is difficult to grow in the south due to disease problems. If you try it, provide excellent drainage and keep the foliage dry.

General Information

Scientific name: Juniperus scopulorum

Pronunciation: joo-NIP-er-us skop-yoo-LOR-um

Common name(s): Rocky mountain juniper, Colorado redcedar

Family: Cupressaceae

USDA hardiness zones: 4A through 9A (Figure 2)

Origin: native to North America

Invasive potential: not assessed/incomplete assessment

Uses: screen; specimen; highway median; bonsai

Description

Height: 30 to 40 feet

Spread: 10 to 15 feet

Crown uniformity: symmetrical

Crown shape: pyramidal, columnar

Crown density: dense

Growth rate: slow

Texture: fine

Foliage

Leaf arrangement: opposite/subopposite

Leaf type: simple

Leaf margin: entire, terminal spine

Leaf shape: scale-like

Leaf venation: none, or difficult to see

Leaf type and persistence: evergreen, fragrant

Leaf blade length: less than 2 inches

Leaf color: green, blue or blue-green

Fall color: no color change

Fall characteristic: not showy

Flower

Flower color: unknown

Flower characteristics: not showy

Fruit

Fruit shape: cone, round

Fruit length: less than 0.5 inch

Fruit covering: fleshy

Fruit color: blue

Fruit characteristics: attracts birds; showy; fruit/leaves not a litter problem

Trunk and Branches

Trunk/bark/branches: branches don't droop; not showy; typically multi-trunked; thorns

Pruning requirement: little required

Breakage: resistant

Current year twig color: brown, gray

Current year twig thickness: thin

Wood specific gravity: unknown

Culture

Light requirement: full sun

Soil tolerances: sand; loam; acidic; alkaline; well-drained

Drought tolerance: high

Aerosol salt tolerance: unknown

Other

Roots: not a problem

Winter interest: no

Outstanding tree: no

Ozone sensitivity: unknown

Verticillium wilt susceptibility: resistant

Pest resistance: resistant to pests/diseases

Use and Management

There are many cultivars of this plant available to consumers due to the efforts of nursery operators. Only a small sample of their variability will be presented here. 'Gray Gleam'—silvery gray foliage, pyramidal, slow growing to 15 feet in 30 years; 'Skyrocket'—very narrow columnar growth, bluish green foliage. After the plant reaches about 15 feet tall (after about 10 to 15 years) it is subject to bending of the lateral branches, some to the ground, ruining its form. 'Table Top'—semi-upright, flat-topped growth habit, silvery gray foliage, 5 feet high in 10 years; 'Wichita Blue'—bright blue cast to foliage, pyramidal form.

Pests

Bagworm caterpillars web foliage and debris together to make bags up to two inches long. The insects live in the bags and emerge to feed on the foliage. Use sprays of Bacillus thuringiensis. The insects can also be picked off the plants by hand.

Juniper scale causes yellowed needles, and infected branches fail to produce new growth. The scale is round and at first white, later turning gray or black.

The juniper webworm webs twigs and needles together, causing them to brown and die. The larva is 1/2-inch-long and is brown with darker stripes. The larvae are often in the densest part of the plant and can go unnoticed.

Mites cause stippled and bronzed foliage.

Diseases

Twig blight causes death and browning of twigs tips. The disease may progress down the stem killing the whole branch. Small lesions may be seen at the base of dead tissue. Prune out dead branch tips.

Three rust diseases seen most often are cedar-apple rust, hawthorn rust, and quince rust. Cedar-apple is the most common. On juniper the disease forms galls and orange jelly-like horns in spring. The horns are most likely to form following periods of rainy, warm weather. Spores formed in the horns infect the alternate host. The diseases are more serious on the alternate host than juniper. A separation of a few hundred yards may help avoid the disease. Prune out the spore horns when seen in the spring.

Junipers are not tolerant of ice coatings. Expect dieback when junipers are covered with ice for several days. Removing the ice is impractical.