Blue rug juniper, also known as juniperus horizontalis or "Wiltonii" juniper, is a creeping plant that is prized for its use as a ground cover in hot, dry conditions. Although blue rug juniper will tolerate environments as far north in the United States as southern Minnesota, Wisconsin and Michigan, it prefers warmer and drier environments, including those in the Rocky Mountains and the Southwest.
Blue rug juniper is especially well-known for its ability to thrive in nearly any type of soil conditions. Although it prefers moist, well-drained soil and cannot tolerate excessively damp ground, blue rug juniper will grow well in a wide variety of soil conditions, including compacted soil, dry soil, urban environments, and soils with widely variable pH or acid/base readings. Its tolerance for varied soil conditions makes blue rug juniper a solid choice for ground coverings in urban areas, irregularly shaped areas, or places where mowing and watering are infrequent.
Blue rug juniper grows horizontally across the ground rather than upwards. Most plants only reach about four inches tall. The leaves of blue rug juniper are bright blue in spring and summer and a darker reddish-blue in winter. The leaves feel soft and scaly to the touch. The plant's stems are woody and red or reddish-purple, often hidden behind the leaves. Blue rug juniper in the wild often has dark blue berries that take two years to fully form; however, cultivated plants rarely develop berries.
The plants tolerate heat, drought, poor soil, trampling, and regular cutting or shearing well, making them an ideal ground cover for yards with little water. However, they cannot tolerate salt spray, full shade, or excessive water. Blue rug juniper growing in an environment that is too wet often suffers from disease or infestation by pests like scale, aphids, and mites that feed on the plants.
With these facts about blue rug juniper and the right growing environment, blue rug juniper can be a great addition to your garden or landscape design.