The Blue Rug Juniper (Juniperus horizontalis ‘Wiltonii’) is a highly valued, low-maintenance evergreen groundcover. Its dense, trailing habit makes it an excellent choice for stabilizing soil on inclined landscapes. This guide walks through the specific preparation and planting techniques necessary to successfully establish Blue Rug Juniper on a slope.
Site Preparation and Optimal Spacing
The Blue Rug Juniper thrives best when planted in an area that receives full sun, meaning at least six hours of direct sunlight daily. While this species is highly adaptable, selecting a location with adequate drainage is beneficial, as junipers dislike consistently saturated roots. This evergreen is known for its tolerance to poor soils, but heavy clay that retains too much water should be avoided or amended.
Clear the entire area of existing weeds, grass, and other competing vegetation before planting. Aggressively removing these competitors ensures the young juniper has access to all available water and nutrients during establishment. For larger areas, applying a non-selective herbicide several weeks prior to planting can efficiently reduce the weed seed bank and perennial grasses.
For slopes, planting should generally occur at intervals of 6 to 8 feet apart, measured center to center. This calculation balances the need for rapid coverage with the mature plant’s expected spread of 6 to 10 feet. Closer spacing is often prioritized on steeply sloped terrain to hasten the formation of protective coverage.
Specific Planting Technique for Slopes
When digging the hole on an incline, aim for a diameter that is at least twice the width of the root ball, but only as deep as the root ball itself. This wider hole provides loose soil for the juniper’s roots to spread quickly into the surrounding area, which is important for firm anchoring on a slope. It is necessary to position the top of the root flare—where the roots meet the stem—level with the surrounding soil line.
On a slope, it is often beneficial to plant the root flare slightly higher than the surrounding soil to accommodate for future settling and to prevent water from pooling at the stem. To counteract the natural pull of gravity and potential erosion, carefully angle the plant slightly toward the uphill side of the slope. This subtle angling helps the plant’s developing root system anchor more securely into the bank as it grows.
A technique specific to slope planting involves creating a shallow, crescent-shaped berm of soil on the downhill side of the plant. This small ridge acts as a miniature terrace, temporarily capturing water and directing it down toward the root zone rather than allowing it to immediately run off. This simple modification is particularly beneficial for young plants not yet established enough to withstand heavy rainfall erosion.
Backfill the hole with the original soil, gently tamping it down to remove large air pockets. Avoid excessive compaction, which can impede root growth and water percolation in the dense soil of a hill. Once the hole is filled, the plant should be secure, and the newly created berm should be ready to capture the first watering and subsequent rainfall.
Initial Watering and Long-Term Establishment
After planting, apply water slowly to prevent surface runoff from washing away the soil and disturbing the new plant. Using a soaker hose or a drip irrigation system is the most efficient method to ensure water penetrates the root zone effectively without causing erosion.
Applying mulch is important for moisture retention and weed suppression, but the technique must be adapted for inclines. Use a heavier, coarser type of organic mulch, such as wood chips or shredded bark, which is less likely to migrate downhill than fine materials. The mulch layer should be applied thinly, generally no deeper than two inches, and must be kept several inches away from the juniper’s central crown to prevent moisture-related rot.
During the first year, consistent moisture is necessary for the juniper to establish its extensive root system. Check the soil moisture regularly, providing supplemental water during extended dry periods or times of intense heat, especially in the summer months. Once established, this species becomes highly drought tolerant and requires minimal intervention. Pruning is rarely required, except to remove dead or damaged branches.