By C Rae Hozer
UT Gardens—Crossville has colorful shrubs and small trees (in addition to the Weigela florida varieties cited in recent "Plateau Gardening" columns).
Mary’s Garden sports two crape myrtles with dark burgundy leaves: Delta Flame (Lagerstroemia indica "Delec") and Delta Eclipse (L .indica "Deleb"). Differentiate them by their panicle colors. Delta Flame has dark coral-red blooms and Delta Eclipse pinkish-purple ones. These plants are smaller now because they were just installed in 2012, but both are expected to be medium sized for the species (at maturity 6 to 10 feet high with about that same spread). Their hardiness range is zones 7a– 9b (tolerating cold as low as zero degrees Fahrenheit). That means these selections should be suited to most parts of Tennessee but might be problematic in landscapes at higher elevations.
Last winter, the Crossville area had milder than average temperatures but folklore-signs this fall such as an abundance of dark wooly bear caterpillars indicate conditions may be harsher during winter 2013-'14. Recorded temperatures for the Cumberland Plateau north of the city have earned this place a designation of USDA plant hardiness zone 6b (average low temperature minus 5 degrees F) and gardeners with experience here know that plants growing outside their cold-weather range are actually at greater risk during abrupt temperature fluctuations which are typical in springtime than during a constantly cold winter season. Currently these crape myrtles seem to be thriving, but I wouldn’t rush to add them to a zone 6 landscape. If they still look good in Mary’s Garden two years from now they will have earned the confidence of homeowners in the Upper Cumberlands.
Two specimens with colorful foliage that grow in the Master Gardener theme garden "Home on the Plateau" should be safer bets in cold weather. Black Lace elderberry (Sambucus nigra "Eva" Black Lace) is a showy deciduous shrub with fragrant flowers and fruit that is edible. This cultivar thrives in hardiness zones 4a (low minus 40 degrees F) through 7b (to 5 degrees F). The deeply lobed leaves have a lacy texture similar in appearance to the finely cut foliage of some Japanese maples. In full sun the foliage is such a deep purple it seems almost black. Young stems are purple as well but turn a brownish hue with age. Grow in moist but well-drained soil.
At maturity this upright bush is typically six to eight feet tall. Pruning in late winter will eliminate some blooms but encourages branching for a full-bodied form with more pretty leaves and/or can be done to control shrub size. In June many tiny pink flowers which scent the air with the smell of lemons together form large (as much as 10 inches across) flat inflorescences. Butterflies are attracted to the flowers. Clusters of elderberries follow. The fruits attract birds and other wildlife.
Coppertina ninebark (Physocarpus opulifolius "Mindia" Coppertina) has showy layers of multicolored leaves. The foliage makes you stop and take notice. In spring new leaves are a coppery-orange color with red margins. Given a sunny location with dry to average soil, the foliage ages to become a rich red edged with burgundy that contrasts well with the off-white button-shaped blooms in summertime. Increase foliage density during the first two years after transplant by repeatedly pinching or shearing off an inch or two of new growth at branch tips. This cultivar is hardy in zones 3a (low minus 40 degrees F) through 7b (to 5 degrees F).
This article is the last for the 2013 season. Send email comments, topic suggestions and/or yard and garden questions to Master Gardener Rae, MGardenerRae@frontiernet.net.
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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.