Microenvironment and Transplanting
Michael R. Rachinsky, Ph.D., Nanuet, New York
Gardeners for years have noted a practice that I think bears a few remarks concerning the transplanting of rhododendrons, i.e. removing "soil" from a potted plant before placing it into its new site.
Many rhododendrons are potted in a high sphagnum peat media (+- 30 per cent by volume). This appears to be a highly acceptable practice. The writer has followed the practice himself.
The result has been the loss of a few fine plants. To such losses one could attribute a lack of plant hardiness. In fact the plants literally "starved" to death in their own micro-garden. Upon examination the very fine roots of the rhododendrons could be seen as never having left the initial peat ball. In some cases they actually grew inward.
Suggested remedies are: 1. Do not pot in a high peat medium. After the rooted cuttings are taken from their initial beds, usually high in peat, they should be placed in a more natural soil-like environment. 2. Wash or shake off enough soil to expose roots and the plant from the peat ball and place into acceptable garden soil (which may or may not contain a little peat as an extender.) 3. Wash or shake off enough soil to expose roots and place in a medium which contains peat in reducing amounts as one draws circles with larger and larger diameters around the plant. (A method suggested by G. Guy Nearing to the author).
This writer's preference is the use of as little peat as possible. The plant thus forms the less fine roots and more easily adjusts to its new environment. Such obviously could not be practical at all times, i.e. alkaline regions. However, in the example case the site often is also high in peat percentage.
Note that this discussion concerns sphagnum peat. It has been stated that sedge peat is also an excellent extender. This note also applies to the handling of seedlings.