Seedling Culture, One More Time
Dr. Mark Konrad
Sewickley, Pennsylvania

Through the years I have had many varied experiences raising rhododendron seedlings, including many misjudgments and losses.

Much of this can be traced to not fully appreciating the continuum of steps necessary for a successful outcome. Each step is dependent upon the other and must be completely executed for a fruitful culmination. The whole endeavor is only as strong as the weakest link in the continuum.

• INDOOR/OUTDOOR TRANSITION. The transition from indoor to outdoor culture is a very critical stage. If the conditions including temperature and moisture are not just right dormancy can intervene and retard growth.
• OUTDOOR CULTURE. When seedlings are taken outdoors a convenient and continuous method of maintenance should be arranged. Watering and moisture control become very important. Any laxity can lead to enormous losses.
• INSECT AND ANIMAL CONTROL. A method must be arranged to control insect and animal invasion. Failure to do so can lead to decimation of large populations of plants. Examples can include larval stages of insects, sow bugs, mice and chipmunks.
• OVERWINTERING. Over wintering is also a significant issue. Losses can be great if proper protection is not arranged.

Currently, I am using a method which is relatively simple and addresses many of the pitfalls that can occur along the way.

Twenty to twenty-five seedlings are transplanted into 9-inch (22.5 cm) pots with a height of 6 inches (15 cm). The depth of the medium is approximately 1-2 inches (2.5-5 cm), which allows for adequate growing space. Clear plastic sheeting is laid lightly over the pots, both indoors and outdoors. When taken outdoors the pots need appropriate shading and also the addition of overhead plastic paneling to shield from the rain. This is usually positioned 2 or 3 inches (5-7.5 cm) above the pots on my benches.

For overwintering, the addition of burlap or other cloth is placed beneath the plastic sheeting, which allows for extra insulation and the reduction of light and any temperature increase.

The pots can be left on the benches or placed on the ground. With the latter, the plastic panels can be laid lightly over the pots, but there is more vulnerability to animal invasion when on the ground. There is also the option of storing the pots in an unheated garage. In this case only a plastic sheeting cover is needed to conserve moisture.

Some of the advantages are these:

Comment: An artificial mix of equal parts of perlite, Canadian peat and shredded pin bark is recommended. The safest way to use a fertilizer (acid loving) is to spread a small amount on the surface of the medium.

Dr. Konrad is a member of the Great Lakes Chapter.