CROSSVILLE —
I went to the Fall Gardeners Festival at Plateau Discovery Gardens on the grounds of the University of Tennessee AgResearch and Education Center near Crossville at the end of August to pick up continuing education credits for my annual Master Gardener certification and to get the latest scoop from the experts on growing, maintaining and arranging plants in home landscapes so I could pass that information along to “Plateau Gardening” readers. Of course, that is the reason for the education requirement — to ensure Tennessee Master Gardeners have research-based, up-to-date information when answering residents’ horticulture questions.
Since so many folks ask me about hydrangeas, attending Mark Windham’s talk “Hydrangeas: Winners, Losers and How to Care for Them” was a top priority (I caught the question and answer segment at the tail end of his 11 a.m. hydrangea presentation then circled back to hear the entire talk at 2 p.m.)
Dr. Windham’s area of study is entomology (the scientific study of insects) and plant pathology (study and diagnosis of disease) rather than horticulture. Plants stressed by insect infestations, infectious diseases, extreme temperatures (too much heat as well as too much cold) or the wrong amount of sun, moisture and soil fertility don’t perform as well as plants which are free of insect pests and/or health problems and are also installed in a suitable environment. Such university studies into a species or individual plant variety’s tolerance for these various stressors helps when trying to find the best plants for conditions in your gardens and landscape.
Windham has an on-going hydrangea trial at Discovery Gardens to evaluate resistance of various cultivars to the foliar diseases powdery mildew and black spot. For those who may be wondering, the term “cultivar” is horticultural shorthand for “cultivated varieties.” Just think cultivar equals variety. Stop at Discovery Gardens for a self-guided tour and stroll through the hydrangea plot to evaluate how healthy the leaves of different hydrangea cultivars look. Summarized in general, findings indicate hydrangeas that get too much shade exhibit more leaf spot; those receiving too much sun have more powdery mildew.
Tip for those raising hydrangeas at home: To avoid powdery mildew, don’t locate hydrangeas in full shade. To avoid black spot, don’t locate hydrangeas in full sun. When the particular hydrangea specimen you wish to add to your yard is described as needing “full or part sun” or as best in “full to part shade” find a spot to install it that gets at least six hours of mid-season sun early in the day (until 11 a.m. or noon) then shade for the rest of the day.
If you are on site at this hydrangea trial garden also be aware of how few blooms there are. When most of a plant’s energy goes into foliage production there are few flowers. To produce lots of leaves for disease analysis, these hydrangeas have an irrigation system that regularly supplies them with both water and fertilizer. If you want an abundance of blooms, don’t coddle your hydrangea by over-watering and over-fertilizing it. Turn off automatic irrigation. Manually water the hydrangea when there has been scant natural rainfall and its leaves appear wilted in the morning (don’t jump the gun — despite wilted foliage in the afternoon, hold off irrigating until morning). Hydrangeas don’t like wet feet. Where soil is soggy, a hydrangea won’t perform well no matter what you do. Use a mild, broad spectrum fertilizer not one heavy in nitrogen. Fertilize hydrangeas that are remondant (re-blooming) two times per season. Fertilize those that bloom once one time.
•••
Plateau Gardening is written by Master Gardeners for gardeners in Tennessee’s Upper Cumberland Region. UT Extension Cumberland County at P.O. Box 483, Crossville, TN 38557 (484-6743) has answers to horticulture questions, free publications and details on how to become a Master Gardener. Send email comments or yard and garden inquiries to Master Gardener Rae, mgardenerrae@frontiernet.net.
Speak Your Mind