Creeping juniper, Juniperus horizontalis, is a native, mat-forming, evergreen prostrate gymnosperm shrub that has numerous horizontal branches capable of 10 to 20 foot (3-6 m) lengths with a multitude of short erect stems 4 to 10 inches (10 to 25 cm) tall. Creeping juniper has a high frost resistance and tolerant of drought and cold, however, it has low shade tolerance, it is extremely sensitive to competition, and is usually consumed by fire because of the highly combustible resinous foliage. 

Creeping juniper is dioecious with separate male and female shrubs that are slow growing, long lived plants that have poor seed production, low germination rates, high seedling mortality, and rare seedling establishment. Branch segments broken from mature plants can root and develop into separate plants.

Creeping juniper grows in Wisconsin in cedar glades which are eastern red cedar savanna communities on steep hillsides of thin loess over limestone, or of gravelly glacial moraine with a major species component of common juniper, little bluestem, hairy grama, and sand dropseed, and also grows in upper lake dune communities with no true soil but not directly affected by wave action with a major species component of common juniper, sandbar willow, northern wheatgrass, intermediate wheatgrass, prairie sandreed, and canada wildrye (Curtis 1959).

Creeping juniper grows in North Dakota Badlands in little bluestem communities on steep upland slopes with very shallow soils containing exposed scoria outcrops with a major species component of shrubby cinquefoil, skunkbush, woods rose, plains muhly, and threadleaf sedge.

Creeping juniper can grow in deep sands, sandy, sandy loam, loamy, silty, and clay loam soils that are also described as poorly developed or shallow and in open communities with low plant density and little interspecies competition.

The sandy, shallow, and silty ecological sites of the 1983-2012 study had well developed soils; the shallow soils were well developed sandy loam that were relatively thin. The plant communities were

dense with grass tillers of normal height and with very little open spaces and almost no bare ground. These study sites have very different characteristics from the described plant communities where creeping juniper prefers to grow. The well developed soils of the study ecological sites permitted a healthy grass population to flourish. The tall dense grass tillers caused shading and strong aboveground competition for sunlight. The healthy grass root systems caused strong resource uptake competition for belowground nutrients and soil water. Such debilitating conditions would cause severe stresses on creeping juniper plants resulting in little resources for survival and fewer available resources for new growth. The creeping juniper plants were able to exist but unable to produce substantial new growth.

For more information Go To:

https://www.ndsu.edu/agriculture/ag-hub/publications/dickinson-rec-2016-annual-report