The Blue Rug Juniper (Juniperus horizontalis ‘Wiltonii’) is a low-growing evergreen shrub known for its dense, mat-forming habit. This cultivar features striking silvery-blue, scale-like foliage that provides year-round color and interest. It is prized as a ground cover due to its durability and ability to thrive in harsh conditions once established. Its naturally prostrate growth makes it an excellent choice for stabilizing slopes and covering large areas with minimal maintenance.
Selecting the Planting Site and Preparing the Soil
The selection of the planting location is the most important factor for the long-term success of the Blue Rug Juniper. This plant requires full sun exposure, meaning the chosen site should receive a minimum of six hours of direct sunlight daily for optimal growth and foliage color retention. Planting in too much shade will cause the growth to become sparse and leggy, diminishing its effectiveness as a dense ground cover.
The soil requires excellent drainage, as junipers are highly susceptible to root rot in waterlogged conditions. The plant naturally thrives in well-drained, sandy, or rocky soils and is adaptable to a wide range of soil pH levels. Before planting, clear the area of all existing weeds, grasses, and debris to eliminate competition for resources.
If the soil is heavy clay, it must be amended to ensure water does not pool around the roots. Mixing in organic matter, such as compost, aged manure, or coarse grit, will improve the soil structure and increase porosity. This allows excess water to drain away quickly, mimicking the drier conditions the plant prefers. Prepare the soil across the entire planting area, not just in the individual holes, to encourage widespread root establishment.
Proper Spacing and Planting Depth
Correct spacing is necessary to achieve a continuous, dense ground cover carpet without overcrowding the plants. Blue Rug Juniper matures to a spread of approximately 6 to 8 feet, so a typical spacing distance is between 4 and 6 feet apart when a thick mat is the desired outcome. Planting the junipers closer together, perhaps at the 4-foot mark, will result in faster coverage and weed suppression, though it requires purchasing more individual plants.
To begin the planting process, dig a hole that is two to three times wider than the root ball of the container plant, but no deeper. This width encourages the roots to spread outward into the prepared surrounding soil. Before placing the juniper in the ground, inspect the root ball for compactness or circling roots.
For container-grown plants, gently loosen the outer roots with your fingers or lightly score the root ball with a knife to disrupt the pattern of circling growth. The plant must be positioned so that the top of the root ball is level with, or slightly higher than, the surrounding native soil. Planting the juniper too deeply can cause the crown, where the stem meets the roots, to become buried and retain moisture, leading to stem rot.
Once the plant is correctly positioned, backfill the hole with the amended soil mixture, tamping gently to eliminate large air pockets around the roots. Finally, create a shallow, circular berm or ring of soil around the outer edge of the planting hole. This soil ridge acts as a temporary basin to direct water inward toward the root zone during the initial watering phase.
Watering and Establishment Care
Immediately after planting, the juniper requires a deep and thorough watering to settle the soil and eliminate any remaining air pockets. This ensures good soil-to-root contact, allowing the plant to begin absorbing nutrients and water. The water should fill the shallow berm and slowly soak into the ground until the entire root zone is saturated.
During the first full growing season, the Blue Rug Juniper must receive consistent moisture to develop a strong, extensive root system. This usually translates to a deep watering once per week, though this schedule should be adjusted based on rainfall and local temperatures. Before watering, check the soil moisture by sticking a finger about three inches deep; if the soil feels dry at that depth, it is time to water again.
Once the juniper is established, typically after the first year, its watering requirements decrease significantly, as it becomes highly drought-tolerant. Apply a 2- to 3-inch layer of organic mulch across the planting area. Use materials like shredded wood chips or pine needles, ensuring the mulch layer does not directly touch the central stem or crown of the plant.
Keeping the mulch several inches away from the stem prevents moisture buildup around the base, which can lead to fungal issues and rot. Blue Rug Juniper is a low-maintenance plant that generally requires little to no pruning. Any necessary trimming should be limited to removing dead or damaged branches or clipping stray growth.