JARS v48n3 - Rhododendron Garden Dead Spots

Rhododendron Garden Dead Spots
Mark G. Konrad, M.D.
Sewickley, Pennsylvania

Even when a rhododendron garden has ideal environmental conditions, there can be spots where the plants do not flourish to our expectations. We are often mystified by the malady, but we can be prepared to cope with the unfortunate illness and render a satisfactory remedy.
Above ground, sites may be variously influenced by winter cold and wind as well as summer heat and dryness. Below ground, the important factors of soil moisture and pH levels may vary. The soil composition and mineral content may be unsatisfactory in some areas. Isolated pockets of poor soil can occur naturally or be related to the previous detrimental use of the land. Foundation backfilling with excessive lime would be an example. An underground flow of water in some places may be a problem, and areas of poor drainage in other places may also be a problem. Trees can also cause areas of localized dryness, with some, such as maples, being worse than others. Some trees also present excessive shade.
Providing microclimates can be vital to good rhododendron culture. Barrier protection, either artificial or natural, can make a significant difference. By altering wind patterns beneficial effects may ensue, possibly even accompanied by increased humidity during the summer. Generally, rhododendrons do not like hot, dry summers, and this is understandable when we consider that many have their origins in cool, moist climates.
By evaluating the strengths and weaknesses of your garden, sites may be chosen which lead to the best possible cultural settings. When practical, one should not hesitate in moving a plant to a proven area. At other times, prospective sites may be improved following soil analysis. Also, adding organic material or other soil conditioners, such as sand and perlite, may be helpful in some instances.
In summary, an attempt has been made to point out rhododendron garden site deficiencies and to suggest changes which could lead to improved cultural conditions.

Mark Konrad, a member of the Great Lakes Chapter, is a frequent contributor to the Journal. Among his articles are ones on big rhododendron breeders and designing a classic rhododendron garden.