Crossville Chronicle, Crossville, TN

June 3, 2013

Plateau Gardening: Questions about plant identification

By C. Rae Hozer
Chronicle contributor

CROSSVILLE — May in the Neighborhood

Note the picture showing plantings around two mailboxes observed in May. These are my best guesses as to the vegetation species and varieties shown there. At left front are dark violet-blue salvia flower spikes, which may be the hybrid "May Night" Salvia X sylvestris, 1997 Perennial Plant of the Year. The four- to five-inch diameter double lavender clematis blooms with slightly ruffled edges (mid-photo) are a more recent introduction, Clematis vancouver "Sea Breeze." The vine works in a spot like this because of plentiful flowers from late spring into autumn, a compact form and disease resistance. Golden foliage on the creeping Jenny groundcover, Lysimachia nummularia "Aurea" (at center and in front of the long thin daylily leaves on the right) provides a striking contrast to the purple blossoms.

Reader Donna M’s email gave me the idea of printing occasional photos featuring plants seen while walking our dog, Cocoa. The gist of her message: "We recently settled in this area and are not familiar with many of the beautiful flowering shrubs, perennials and trees. I want to learn the names of plants growing on our property. When we telephoned the Cumberland County University of Tennessee Extension office in Crossville, a visit with a Master Gardener Monday through Friday was suggested."

I replied explaining that Master Gardeners, who man the homeowner question and answer desk at the Crossville UT Extension office weekday mornings, might be of assistance, but their primary focus is diagnosing plant problems rather than identifying flowering shrubs and other ornamentals.

Rhododendron Borer Follow-up

Another reader sent an email after seeing the last article to ask what should be done to avoid borer damage to the huge, beautiful rhododendron in her yard. Good question.

The old riddle is true. What is the one thing always seen in a healthy landscape? Answer: the gardener’s shadow. Check your treasured plants in late winter and springtime. A problem that started early in the season may be beyond help if not discovered until late summer or during autumn. Noticing in February the damaged stem on the rhododendron by my driveway alerted me to the possible presence of rhododendron borers. That was confirmed by our county agent after he saw a photo showing the shrub in question.

As a general rule, don’t use insecticides unless the pest or identifiable pest damage has been observed. If a control is to be employed, make it one proven effective against the particular infection or infestation. Apply when the probability of a successful outcome is highest. Permethrin (sold under Astro and other brand names) or bifenthrin (Onyx) are preventive controls for rhododendron and other clearwing borers. Treat rhododendron trunks and branches in May and late June, when adult rhododendron borers are active and larvae which hatch from eggs deposited on the bark are still out in the open. 

Not sure what is making your plant look sick or bad? Your local UT Extension office is the place to go. Physical examples of plant pest or disease problems can be analyzed there and recommendations made for remedies. Cut off a sample displaying symptoms. Put it in a clean plastic bag. Another option is available online. Experts at the UT Extension Soil, Plant and Pest Center post information and photos on the lab’s Facebook page each day about pest and/or disease issues they see. View that page by entering https://www.facebook.com/SoilPlantPestCenter in your web browser.

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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.