JARS v51n3 - 30 Years with Seeds and Seedlings - Part II

30 Years with Seeds and Seedlings -Part II
Mark Konrad, M.D.
Sewickley, Pennsylvania

With success comes the production of hundreds or even thousands of 1 - and 2-year-old rhododendron children. In many respects the real work is just beginning, and we soon learn that all of our creative and organizational skills will be stretched to raise the family.

How we manage the ongoing culture will depend on whether an indoor or outdoor method is used. Regardless of the method, a satisfactory outcome will depend on our ability to organize on a step-by-step basis. This becomes very important so that the method can be reproduced each year. Before describing each method, it must be further stressed that young rhododendrons, like children, need special nurturing. Each way has advantages and disadvantages.

Usually indoors or outdoors it is advisable to carry the young seedlings in flats with two transplantings often needed. After the plants are 4 to 6 inches tall some growers continue on with individual pots.

In the greenhouse, conditions can be highly controlled but are more expensive, labor intensive and involve more risk. With proper temperature control, potting mixes and extended light periods, plant growth can be rapidly accelerated. Quite often the larger potted plants are carried over in unheated poly houses for winter protection. One advantage of the outdoor method is the early loss of many plants not suited to a particular environment.

When indoors it is generally better to use artificial mixes to reduce potential disease problems. The coarse mix of Canadian sphagnum peat moss, shredded pine bark and perlite has proven ideal. Dolomitic lime is added to adjust the pH to 5.5-6.5 and to provide calcium and magnesium. Gypsum is added as a source of essential sulfur and calcium. Phosphate fertilizers have become a standard additive along with fertilizers with trace elements. Wetting agents are frequently used along with Epsom salts (magnesium sulfate) in some instances. Weldon Delp of the Great Lakes Chapter has had great success with his formulations.

When going outdoors an increasing amount of sandy loam can be added to the coarse mix as the plants increase in size. Increments of a broad spectrum fertilizer can also be considered at this time.

Also when outdoors it is mandatory to have proper summer shading and winter protection for the young plants. Either wire or snow fencing can be used, supplemented with plastic covering in the winter and additional cloth shading in the summer.

When outdoors a small amount of powdered sulfur added to the watering can help avoid most insect problems. A recent innovation has been the use of cardboard flats which have greatly reduced outdoor maintenance.

Container for Rhododendron seedlings
Cardboard flats are used for 1 - and 2-year-old seedlings.
Plastic shade fabric is used for summer care
and plastic film for winter protection.
Photo by Mark Konrad

The ever increasing size and number of plants produces an ongoing logistical problem. Some opt to grow in larger containers to flowering size while others transplant the larger plants to natural sites.

When a voluminous number of plants are produced a nursery or factory approach will be needed with considerations for proper maintenance, mulching, shading and irrigation when needed.

In summary, the special and nurturing needs for young plants has been reviewed. If the method is well organized the amount of work is lessened and the losses minimized.

Dr. Konrad, a member of the Great Lakes Chapter, is a frequent contributor to the Journal.