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Journal American Rhododendron Society

Current Editor:
Dr. Glen Jamieson ars.editor@gmail.com


Volume 33, Number 1
Winter 1979

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Hand Pollination Versus Controlled Pollination
By Tue Jorgensen, Virum, Denmark

        It is a sad fact that it takes just as many years to grow an inferior plant as to raise a perfect specimen from seed. As time goes by, you realize that far too much time has been wasted already on growing seedlings of disputable quality, but certain growers demonstrate clearly that it is not at all impossible to raise beautiful plants from hand pollinated seed. I feel that anybody can do the same trick, provided that a few simple but very important rules are observed. The secret is basically divided into two different problems; that is, selection of parents and prevention of contamination.

Selection Of Parents:
        Only rarely does it happen that seedlings of true species are any better than their parents. Therefore, there should be no doubt that, whether you aim to make species seed or to raise the ultimate in hybrids, you should not be satisfied with anything less than the best possible parents for the purpose, even if it may take you some time and effort to select them. When making species seed, you should not expect a certain superior specimen to accept its own pollen; if seed capsules develop at all they will generally be small, contain very little seed, and the seedlings will often lack vigor. The same plant produces capsules of exceptional size with large amounts of viable seed when pollinated with pollen from a different plant of the same species. Naturally this other plant cannot be of the same clone, since this reaction is simply nature's way of preventing degeneration by in-breeding. When using different parents in a pollination, it is wise to let the plant having the most desired qualities bear the seed.

Prevention of Contamination:
        Pollen must be handled with absolutely clean hands and tools. In most cases it is fully developed shortly before the flowers open naturally. Collected at this stage there can be no doubt about the purity. If for some reason the pollen should not be ripe this early, it is essential that the flowers be protected against insects, wind drift of pollen from neighboring plants, etc., so that there can be no risk of contamination before harvesting. These precautions may seem a bit hysterical but actually it takes less pollen than the naked eye can detect to fertilize a vast number of seeds in the capsule; so don't take any chances. The pollen may be temporarily stored in a cool place for a period of 3-4 weeks, provided it is allowed to dry. Stored in a deep-freezer in a completely dry state it will keep its viability for years, and the enthusiast should always build up a private pollen bank as mother nature may not be quite dependable from year to year.
        Pollinating the flowers is the phase which offers the maximum of opportunity for errors. Some flowers have stamens of equal or greater length than the pistil; and in such cases, great care must be exercised in making a hybrid cross, as it is often necessary to remove the corolla and the stamens by loosening them at the base and sliding them forward and away from the pistil to avoid self pollination. Fortunately, the majority of rhododendron flowers have stamens shorter than the pistil and this allows you to attack the stigma from the front. In such a situation, the pollination can be done in a most simple and efficient manner by forcing the flower to open just before it would do so by itself. Seal off the outer part of the pistil using a small strip of surgical tape, which is also called micropore tape. This special tape has the unique qualities for our purpose: that it will keep the pollen in place, allow the air to circulate but prevent damage by foreign elements such as rain, etc., and last but not least it provides 100% protection against unintended pollination. You need not worry about timing, as the pollen will stay in place and perfectly healthy until the stigma decides to become receptive. There can be no overheating in bright sunshine, and with a little practice you will be able to make the whole operation so neatly that even the most cautious of your rhododendron friends will let you loan the only flower bud on their R. roxieanum, flowering for the first time after 30 years. If for some reason the pollination cannot be executed right away, just seal off the stigma leaving a small working space in front of the stigma disc, later allowing you access by cutting off the tape with a sharp knife or a small pair of scissors. After pollination, cover up with a new piece of tape on top of the remains of the old one.

Labeling The Capsules:
        Do not fall into the temptation to identify the capsules by writing on the small pieces of tape as the pistils very often dry out and break loose long before the capsules have ripened. Attach the labels to the pedicels if you want the pollinated flowers labeled individually or at the base of the truss if the pollinations are identical.
        I have no intention of claiming that this is the only way to make a really controlled pollination. It does, however, provide the exhausted businessman with a quick, safe and simple method of producing good seed in comparison with other methods I have tried. Good seed is always in short supply. Just ask Mrs. Ogle or Mrs. Berry. So, why not utilize the time you save this way to make another handful of fat seed capsules for the seed exchange. You can be sure that the seed exchange staff and "somebody out there" will love you for it. Hand pollination, as it is very often executed, only means that the flower was pollinated by the human hand before, after or in between the hybridization efforts done by the bees; and such seed ought to be down rated to the state of open pollination. I think that the term "hand pollination" means nothing; "controlled pollination" means everything.


Volume 33, Number 1
Winter 1979

DLA Ejournal Home | QBARS Home | Table of Contents for this issue | Search JARS and other ejournals