Good and Bad Landscape Plant Selections

By C Rae Hozer, Cumberland County Master Gardener

I didn’t name names last week in answer to the homeowner seeking suggestions for shrubs to replace dead evergreens in his yard. In part that was because I first wanted to emphasize that even good plants can go bad if planted improperly or set out in the wrong spot. There are few truly bullet-proof landscape plants.  Remember, real estate isn’t the only field where the three most important factors are location, location and location.

Some evergreens are finicky about placement. Yews are a prime example. Put a yew in too deep or plant it in wet soil and a nasty case of root rot typically results. Other shrubs that look good in three out of four sites are Japanese hollies and junipers. The one unlucky Japanese holly placed where it has wet feet usually dies from black root rot. Phytopthera is a fungal disease that attacks and kills juniper roots growing in soggy ground.

Other plants develop problems without regard to site. Trees should be long-term residents in any landscape but I can think of ornamental species that rarely last ten years. Purple leaf plum trees are sitting ducks when it comes to black knot. The only remedy for that is to cut out the diseased branches. Soon the chopped up little specimen is so out of shape it is more ugly than ornamental. I love the looks of young dwarf Alberta spruce. The tiny, slow-growing tree has dense but delicate evergreen needles and a perfectly conical shape. With regular spraying to prevent spider mite damage, they keep their good looks. However, I spray as a “last resort” and my two attempts at raising Alberta spruce have both ended badly. Each time spider mites infested one side and sucked the life out of the foliage there. As a result, the needles turned a reddish-brown color and fell off. A bare spot where spider mites kill the foliage never re-grows needles. In the end I become disgusted with the misshapened miniature pine tree and rip it out. Bradford pear trees get brittle as they age and break apart by their ninth or tenth birthday. A chain saw is the only solution for that problem.

You might want to put your home landscaping money on plants with more flower power. Not all lilacs and azaleas flower only in springtime. Some newer cultivated varieties have repeat blooms during the summer or flower first in springtime and again in autumn. The trend in modern plant breeding is selections with abundant blooms and a longer bloom period.

The Encore (brand) azalea trademarked description says it all- “More Blooms, More Often”. University of Tennessee’s Mark Windham tested Encore azaleas for cold hardiness in field trials at LaFollette and Crossville. Dr. Windham’s research found that the five top performing azaleas were Autumn Amethyst (dark lavender flowers), Autumn Cheer (pink), Autumn Monarch (ruffled blooms in orange-pink with red flecks), Autumn Ruby (small ruby red flowers), and Autumn Royalty (large purple blooms). 

A common complaint about older hydrangea cultivars is failure to flower. Today hydrangeas that are reluctant bloomers are being pushed aside in the marketplace by remondant varieties that flower on both new and old wood. When shopping for hydrangeas of this type these are variety names to look for- Penny Mac, Oak Hill, Decatur Blue, David Ramsey, Forever and Ever, Endless Summer, and the newer Dirr Endless Summer selection Blushing Bride. For pictures and reliable hydrangea information visit the United States National Arboretum webpage- “www.usna.usda.gov/Gardens/hydrangeafaq2.html”.

Plateau Gardening is written by Tennessee Master Gardeners about home landscapes and gardening in our state’s Upper Cumberland Region. For answers to specific yard and garden questions or to learn how to become a Master Gardener contact UT Extension Cumberland County, P.O. Box 483, Crossville, TN 38557, (phone 931-484-6743). Email inquiries to “mgardenerrae@frontiernet.net”. Email questions may be answered either individually or through future newspaper articles.