Juniperus osteosperma

Utah juniper

Cupressaceae

The Basics

USFS Plant Database

Flora of North America

Utah juniper is a short tree that may live as long as 650 years. Utah junipers grow less than 8 m and are often as short as 3-4.5 m, with a trunk 10-30 cm thick.

Utah juniper is the most common tree in the Great Basin and is widely distributed throughout the arid West...Utah juniper is a climax species in a number of pinyon-juniper (Pinus-Juniperus spp.), sagebrush (Artemisia spp.)-grassland, and shrub-steppe habitat types...Utah juniper is not shade tolerant. It is a climax species in harsh areas where stands are open and regeneration can occur without competition for light.

Utah junipers have a taproot that extends deep into the soil (as far 4.5 m) and lateral roots that may extend as far as 30.3 m from the tree, several inches below the soil surface. Most root biomass is within the first 0.9 m of soil, with fine roots concentrated in the uppermost 46 cm or just below the soil surface.

Juniper litter has an allelopathic effect on some understory species, especially Idaho fescue (Festuca idahoensis), Sandberg bluegrass, and blue grama...Cheatgrass does not appear to suffer from allelopathic effects, and fourwing saltbush (Atriplex canescens) growth increases under juniper canopies.

The accepted scientific name for Utah juniper is Juniperus osteosperma (Torr.) Little (Cupressaceae).

In northwestern Nevada, Utah juniper hybridizes with western juniper (J. occidentalis). In Arizona, Utah juniper hybridizes with oneseed juniper (J. monosperma), Rocky Mountain juniper (J. scopulorum), and alligator juniper (J. deppeana).

Utah juniper is a climax species in a number of pinyon-juniper (Pinus-Juniperus spp.), sagebrush (Artemisia spp.)-grassland, and shrub-steppe habitat types. At the Idaho National Engineering Laboratory Site, Utah juniper dominates with big sagebrush (A. tridentata), antelope bitterbrush (Purshia tridentata), and threetip sagebrush (A. arbuscula), on areas with bluebunch wheatgrass (Pseudoroegneria spicata), needle-and-thread grass (Hesperostipa comata), Thurber's needlegrass (Achnatherum thurberiana), and Sandberg bluegrass (P. secunda).

In Utah pinyon-juniper sites, Utah juniper dominates with singleleaf pinyon (Pinus monophylla), Saskatoon serviceberry (Amelanchier alnifolia), threetip sagebrush, black sagebrush (Artemisia nova), big sagebrush, desert ceanothus (Ceanothus greggii), curlleaf mountain-mahogany (Cercocarpus ledifolius), true mountain-mahogany (C. montanus), green rabbitbrush (Chrysothamnus viscidiflorus), Stansbury cliffrose (Purshia mexicana var. stansburiana), antelope bitterbrush, desert snowberry (Symphoricarpos longiflorus), blue grama (Bouteloua gracilis), cheatgrass (Bromus tectorum), bottlebrush squirreltail (Elymus elymoides), sheep fescue (Festuca ovina), galleta (Hilaria jamesii), prairie junegrass (Koeleria macrantha), Indian ricegrass (Achnatherum hymenoides), western wheatgrass (Pascopyrum smithii), Sandberg bluegrass, bluebunch wheatgrass, and needle-and-thread grass. (Plant Database)

Identification

Shrubs or trees monoecious, to 6(--12) m, multi- or single-stemmed; crown rounded. Bark exfoliating in thin gray-brown strips, that of smaller and larger branchlets smooth. Branches spreading to ascending; branchlets erect, 3--4-sided in cross section, about as wide as length of scalelike leaves. Leaves light yellow-green, abaxial glands inconspicuous and embedded, exudate absent, margins denticulate (at 20); whip leaves 3--5 mm, glaucous adaxially; scalelike leaves 1--2 mm, not overlapping, or, if so, by less than 1/10 their length, keeled, apex rounded, acute or occasionally obtuse, appressed. Seed cones maturing in 1--2 years, of 1--2 sizes, with straight peduncles, globose, (6--)8--9(--12) mm, bluish brown, often almost tan beneath glaucous coating, fibrous, with 1(--2) seeds. Seeds 4--5 mm. (Flora of North America)

Threats

Utah juniper is not shade tolerant. It is a climax species in harsh areas where stands are open and regeneration can occur without competition for light.

Utah juniper is usually killed by fire, especially when trees are small. However, Utah juniper habitat types rarely have sufficient fine fuels to produce severe or continuous fires.

Phenolic compounds produced by the trees reduce ground cover and therefore further decrease fuel loading around the tree. Sites that are most likely to burn are those with small, scattered trees with sufficient herbaceous understory, or those with large, decadent trees able to sustain a crown fire under windy conditions.

Juniper stands are seldom dense enough to carry a crown fire from one tree to the next, so even if one tree is struck by lightning, a fire that burns throughout the stand may not result. (Plant Database)

Reproduction

Utah juniper is monoecious and sometimes dioecious. It reproduces by seeds in cones and produces abundant seeds in most years or every couple of years. Cones have 1 or 2 seeds. The seeds have dormant embryos and impermeable seedcoats, so they need a period of "after-ripening" and usually germinate the second season following maturity.

Utah junipers begin to produce seed only when they are about 30 years old. Utah juniper seeds are long-lived. In one study, 17% of Utah juniper seeds germinated after 45 years. In general, about 8 to 49% of Utah juniper seeds germinate. Animal transport of seeds is an important factor in the dissemination of juniper seeds, especially by jackrabbits. Seeds that have passed through the digestive tract of animals germinate more quickly than those that have not. (Plant Database)

Species Distribution

Utah juniper is the most common tree in the Great Basin and is widely distributed throughout the arid West [67,80]. The tree occurs occasionally in southern Idaho, southern Montana, and western Wyoming, and is common in Colorado, Utah, Nevada, New Mexico, Arizona, and southeastern California. Utah juniper is the most common juniper species in Arizona. (Plant Database)

Citation

USDA Plant Database http://plants.usda.gov/characteristics.html USDA, NRCS. 2016. The PLANTS Database (http://plants.usda.gov, 4 February 2016). National Plant Data Team, Greensboro, NC 27401-4901 USA.

Flora of North America http://www.efloras.org/flora_page.aspx?flora_id=1 Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 19+ vols. New York and Oxford.

Silvics of North America Burns, R.M., and B.H. Honkala. 1990. Silvics of North America (Volume 1: Conifers, Volume 2: Hardwoods). USDA Forest Service Agricultural Handbook 654.

Intermountain Herbarium http://intermountainbiota.org/portal/collections/harvestparams.php Consortium of Intermountain Herbaria. 2016. http//:intermountainbiota.org/portal/index.php. Accessed on February 04.

Burke Museum Plant Image Collection The plant image collection at the Burke Museum, University of Washington.

Jepson Manual http://ucjeps.berkeley.edu/eflora/ The Jepson Manual: Vascular Plants of California. B.G. Baldwin, D.H. Goldman, D.J. Keil, R. Patterson, T.J. Rosatti, and D.H. Wilken [editors]. 2012. 2nd edition, thoroughly revised and expanded. University of California Press, Berkeley, CA., hardcover; 1600 pages. ISBN-13: 978-0520253124.

USGS Plant Species Range Maps http://esp.cr.usgs.gov/data/little/ Critchfield, W.B., and Little, E.L., Jr., 1966, Geographic distribution of the pines of the world: U.S. Department of Agriculture Miscellaneous Publication 991, p. 1-97. Little, E.L., Jr., 1971-1978, Atlas of United States trees, volume 1,3,13,17, conifers and important hardwoods: U.S. Department of Agriculture Miscellaneous Publications.