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Rhododendron ABC's #11

In our previous discussions of the various aspects of rhododendron culture, little emphasis has been placed on the rewards and pleasantries of growing and studying rhododendrons as a hobby. One can obtain a lot of satisfaction from just growing and cultivating known species and hybrids of these colorful and interesting plants. Many enthusiasts have, however, found that their greatest rewards have come from hybridizing-that is, combining two plants with interesting traits to produce offspring with new, and occasionally, superior traits never seen before!

How is this accomplished? There is not sufficient space to discuss all of the various aspects of the science of genetics (the study of inheritance of traits from one generation to the next). But, I should like briefly mention the techniques involved in crossing rhododendrons to produce new individual plants. All of us know that rhododendrons belong to the great congregation known as flowering plants. Each flower has male and female organs in the same flower. These organs produce what are known as gametes (either of two mature reproductive cells, an ovum or a sperm), that in uniting produce a zygote, which can then develop into a new individual of a subsequent generation. In the flower, the ovum is produced in the ovary and the sperm or pollen cell is produced in the anther.

Without going into further detail, we can say that one can obtain a new series of zygotes, that show themselves as seeds, by placing pollen from the male anthers from any flower on the stigma of the same or another flower. The stigma is connected to the ovary by the style. If the stigma is receptive and sticky, the pollen grains grow quickly down the style, enter the ovary and combine with an ovum to produce a zygote, which is nurtured in the ovary to produce an embryo encased in a small capsule that we call a seed.

After sufficient time has elapsed, say five or six months, the ovary develops into a seed capsule which can be harvested, dried and opened to release seeds containing embryos with new, and, hopefully, exciting traits. All of this seems straight forward and relatively simple and it is! However, nature is inherently tricky and it can be shown mathematically that in each cross we are playing a genetic lottery.

Because of the way traits are passed down through chromosomes (threads of little messengers and controllers called genes), the chance of obtaining new individuals with all of the hoped for and desired traits is pretty small. To be certain, one would need to grow hundreds, if not thousands, of seed from each cross. Space requirements, of course, prevent this, so we plant relatively few seeds and hope that we are lucky!

So the hybridizer (hobbyist) keeps trying and each blooming season looks forward to winning the genetic lottery (it does happen once in a while). Perhaps the whole hybridization experience can be summed up by remembering what one droll English hybridist remarked. He said, rhododendron crossing is very rewarding. It consists of years of anticipation and only one day of disappointment, the day the new hybrid blooms!

In the next ABCs, I should like to share the methods I have developed for planting seeds and raising new individual plants. These methods are certainly not the only way to accomplish this goal, but they do result from more than 30 years of experience in searching for the elusive winners from the genetic lotteries!

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Dave Goheen