By C. Rae Hozer
"Plateau Gardening" readers may recall Mike, who gardens in the Crossville area, asked in a June article the most advantageous time to relocate a rhododendron shrub. Mid- to late-autumn (after leaves have dropped from deciduous trees and shrubs indicating plants have entered their dormant phase) up through February is the most beneficial period for transplanting woody-stemmed species in our state.
Each transplanted tree or shrub needs to re-establish its root system at the new location. That takes about two years. Until roots regenerate, the transplant cannot bring moisture in efficiently. Irrigation is required to compensate for lessened root capacity. Pot-grown nursery stock can be set out year round. However, where transplants are of the same species, size and basic pre-transplant health; specimens installed in late-autumn or during winter have an advantage over those that are spring-planted. Producing new shoot growth, leaves, flowers and seeds in springtime and summer leave little energy to fuel root mass development. Hot, dry summer days can seriously stress impaired roots with a heavy demand for water. Since the ground rarely freezes to any appreciable depth during a Tennessee winter, roots of an autumn transplant have a couple months to grow without competition from spring above-ground growth and to better prepare for summertime heat.
While not the right time to transplant trees and shrubs, August is good time to do preparatory research. Learn the sunlight and moisture requirements for perennial plants you wish to add to your landscape. Allowing enough space for a plant’s mature size is important, too. Select the best available spot on your property to meet the needs of each species. Observing the negative effects of our unusually rainy spring and summer on plants in home landscapes should help raise gardener-awareness of the potential harm in iffy plant placements and lax maintenance practices.
Abundant and persistent rainfall can encourage an explosion of plant diseases and insect problems. Fungal problems develop both when a plant’s growing area is damp and cool (during springtime and autumn) and/or when it is damp and warm (in spring and summer). Fungal and bacterial plant diseases grow well, multiply and spread when plant surfaces are moist. Sometimes splashing rain spreads diseases from plant to plant. Sometimes winds carry disease spores. Insects can be disease vectors, too. Insect numbers stay high when plants are close-growing. Crowded plants create a humid environment as do frequent rain storms. Since treatments to stop the spread of fungal diseases must be reapplied to plant surfaces after each heavy rain, in a year like this, home gardeners may get discouraged thinking they’ll go broke buying commercial spray products to stop plant diseases and insect infestations.
Some gardening choices caused few problems in the past but have come back to haunt me in 2013. My mixed fescue lawn looks lush and green at first glance, but a closer look reveals lots of weeds. If only I had raced out to spray broadleaf weed killer on one of the two days three weeks ago when there was no rain forecast. White powdery mildew dusts the leaves of tall garden phlox in a bed to the left of our front porch. Modern phlox cultivars are resistant to this disease, but openly-pollinated hybrid phlox usually produce seedlings that are highly susceptible to powdery mildew. I should have cut off the seed heads last fall or spread a pre-emergent weed killer this year to keep those seeds from sprouting.
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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.