Crossville Chronicle, Crossville, TN

June 11, 2013

Plateau Gardening: Groundcover junipers provide erosion, weed control

And they look nice, too!

By C. Rae Hozer
Chronicle contributor

CROSSVILLE — This spring my neighbor gave up attempts to grow turfgrass on a south-facing slope from the edge of his woods down to the roadside. He replaced the lawn with groundcover junipers surrounded by mulch. Groundcover junipers provide erosion control, weed control and have attractive evergreen foliage.

The silvery, blue-green foliage on these low-lying plants makes me think they are Juniperus horizontalis Wiltonii. A short, dense carpet-like growth habit and bluish colored, scale-like, evergreen leaves inspire this plant’s common name "Blue Rug Juniper." This variety is a great choice for mass plantings on banks or in rock gardens.

This juniper’s zone 3 to 9 hardiness range makes it perfect for most Tennessee landscapes. The plants thrive in full sun and are happiest in soil with an acidic pH that is moist but well drained. If transplants get more water during the first year or two while their roots become established, the variety is not bothered by subsequent periods of drought.

Blue Rug Juniper tolerates diverse unfavorable conditions (compacted soil, dry soil or less than ideal acid/alkaline soil pH readings). It can be a solid performer in locations where other plantings struggle and is especially useful where mowing and watering are difficult. However, Blue Rug Juniper should not be placed in soggy soil, deep shade and/or where air circulation is poor. These conditions are known to weaken the plant causing health problems, insect infestations or death. As long as those three exceptional situations are avoided, Blue Rug Juniper makes a low maintenance addition to your landscape which has a year-round, good looking appearance.

Allowing sufficient space for growth of groundcover junipers is important. The mature size expected for a Blue Rug Juniper is four to six inches in height and a spread of six to eight feet. That means small juniper transplants (a width of about 12 inches by three or four inches in the case of my neighbor’s plantings) need room to grow. Their growth rate is moderate. When spaced four to six feet apart they should over time become dense enough to crowd out weeds.

Use mulch to control weeds after transplanting. Do not pile mulch over the plant crown. Don’t let fallen leaves or branches smother young plants in autumn. Young shoots can be pruned slightly in June to encourage branching. Use caution when pruning older branches. If cut back severely they may not produce new growth. Mature plants that have grown too close together may require thinning to avoid diseases encouraged when air circulation is poor.

Some varieties of J. squamata and J. procumbens are suited to groundcover use as are the J. horizontalis varieties Blue Rug, "Prince of Wales" (green foliage) and "Mother Lode" (greenish-gold foliage). The Japanese garden juniper "Nana" is a groundcover juniper that has been growing in the tree and shrub garden at Plateau Discovery Gardens about eight years. J. procumbens "Nana" has lush blue-green foliage and grows up to one foot tall with an expected spread of up to four feet. Plants set out in 2005 have completely grown together. 

Readers in the Crossville area should stop to view the various theme gardens and University of Tennessee ornamental trials within the Discovery Gardens complex which are open for self-guided tours daily during daylight hours. Plant specimens are labeled. Plateau Discovery Gardens, the most recent addition to the UT Gardens system, is located just south of I40 exit 311 Plateau Rd., off Hwy 70 N at the University of Tennessee Plateau AgResearch and Education Center, 320 Experiment Station Rd. See locator map. The entrance and free parking are located behind the office.

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Plateau Gardening is written by Master Gardeners for gardeners in Tennessee’s Upper Cumberland Region.  Contact UT Extension Cumberland County at P.O. Box 483, Crossville, TN 38557 (484-6743) for answers to horticulture questions, free publications and how to become a Master Gardener. Send email comments or yard and garden inquiries to Master Gardener Rae, MGardenerRae@frontiernet.net.