For the homeowner who has a sloping section of yard which is difficult to maintain, Blue Rug juniper plants may offer a solution.
A Dioecious Shrub
Blue Rug juniper, or Juniperus horizontalis 'Wiltonii', is a very popular cone-bearing evergreen shrub of the family Cupressaceae. This juniper variety is dioecious, meaning the plants must have both male and female plants in the same area to propagate. The female plant is distinguished by the quarter inch long bluish silver juniper "berries" common to junipers. These "berries" are actually seed-bearing cones. The juniper does not produce blossoms. Because Blue Rug junipers use pollen to propagate, those with allergies to pollen should take care.
Physical Appearance
The bluish green foliage of the Blue Rug juniper has a silver cast to it. In winter, the striking coppery purple of the foliage stands out against the stark white landscape.
This cultivar grows to under six inches but it is not the shortest juniper variety. Mature Blue Rug shrubs can grow to five or six feet in diameter. When planted between four to six feet apart, Blue Rug junipers will have a carpet-like appearance when viewed from above. Some sites recommend spacing young Blue Rug junipers six to ten feet apart.
Best Location For Planting
Blue Rug junipers tolerate winters where there are sub-zero snaps and is recommended for USDA Plant Hardiness Zones 3 to 9.
This cultivar will grow somewhat slower when planted in a location with a half day of sun. To avoid the shrubs becoming straggly, they should be situated in a full sun location. The soil should be on the acidic side (5.1 to 6.0 pH). Again, Blue Rug junipers will tolerate soil which is less acidic but will not grow as well as in the right conditions.
One thing which may not be compromised is the amount of drainage in the soil. Blue Rug junipers do not tolerate being left in standing water. They can tolerate drought conditions. For this reason, many landscapers plant these junipers on sloping terrain because the slope allows the soil to drain well.
To encourage young Blue Rug juniper plants to get a good start, mulch around the plants but do not put mulch on the plant crowns. Mulch prevents weeds from growing and competing with the junipers for nutrients and water. Young shoots should be nipped back to encourage branches to spread out.
Reasons For Popularity
Blue Rug juniper plants work well in controlling erosion on sloping terrain. This is the biggest reason for the juniper's popularity.
It is also an excellent plant for a large rock garden. Blue Rug junipers are wonderful groundcover plants which will quickly spread with little maintenance or attention needed, unlike flowering groundcover plants. While these shrubs will cover the ground, reaching full maturity in about ten years under perfect conditions, they are not the quickest growing juniper. That title belongs to Juniperus horizontalis 'Prince of Wales'.
Many juniper species can fall prey to disease but Blue Rug junipers have a fairly good resistance to those diseases. It is also tolerant to hot, humid, or windy conditions.
While this cultivar prevents some weed growth because of its carpet-like growth pattern, it is not the best plant for that job. Juniperus sabina 'Tamariscifolia' does it better.
Care of Mature Junipers
Blue Rug junipers do not tolerate fallen branches or leaves from other trees or any other vine or plant topping its foliage.
Mature plants can have some foliage lightly pruned as they grow larger. This will allow air to get under and around the plants, an important preventative step to keep disease from infesting the junipers.
Resources:
Beaulieu, David . "Blue Rug Juniper Plants." About.com: Landscaping. 23 May 2009 <landscaping.about.com/od/groundcovervines1/p/blue_ju niper.htm>.
"Blue Rug Juniper plant info and purchase." Juniper Trees .com - juniperus garden plants. 23 May 2009 <http://www.junipertrees.com/blue-rug-juniper.html>.
"Juniperus horizontalis ( Blue Rug Juniper )." Backyard Gardener, Your Gardening Source with Gardening Tips. 23 May 2009 <http://www.backyardgardener.com/plantname/pd_25ad.ht ml>.
"PlantFiles: Blue Rug Juniper, Creeping Juniper Juniperus horizontalis 'Wiltonii'." Dave's Garden. 23 May 2009 <davesgarden.com/guides/pf/go/207/>.