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Journal American Rhododendron Society

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Dr. Glen Jamieson ars.editor@gmail.com


Volume 53, Number 3
Summer 1999

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Tips for Beginners: Rhododendrons From Seed - A Cautionary Tale
M. J. Harvey
Victoria, British Columbia
Canada

Reprinted from the Victoria Chapter Newsletter, February 4, 1999

        Growing rhododendrons from seed is a little like politics. You vote for a party and then find out that you didn't have enough information. What you thought they were going to do turned out to be quite different from what you got.
        Thus it is with rhododendrons from seed - you never quite know what you are going to get. And furthermore it may take about eight years to find out, which is about as long as it takes to get the average government to change.
        Now don't let me put you off sowing some seeds by stating the above. Growing rhododendrons from seed is real fun, albeit slow-motion fun. And it is what we, as a society, are mandated to do as one of our functions. My aim is to encourage you to try seeds, but you need to know the equivalent of the party policy.
        So you think you buy a packet of seeds and that the offspring will come up just what the label says? Like radishes? Think again. The world is more complicated than that.
        The purpose of this article is to put down a geneticist's experience and to tell cautionary tales as to what you may expect from particular batches of seeds. I will go through some of the joys and pitfalls of what can happen. And this will just touch on the genetic side, not the practicalities of germinating seeds and growing on the seeds successfully. That is another problem entirely and has been touched on several times in recent years...
        This article is about genetic problems, but first let me digress to human problems. These include several uncontrollable factors which bear on the seedling results. I include here the skills of the individual producer and the care and attention he or she puts into producing the seed supplied.
        Some people are very good at producing seed accurate to the label. These are the majority, I think. Others are less careful or do not understand the process of pollination and how to control what happens. The problem of "beating the bees," I call it. I have seen plants labeled as a certain hybrid that were better explained as the result of an accidental self-pollination. The fact that the hybridizer thought they were hybrids, or that the label on the packet said a certain thing, may have to be reexamined in the light of the results.
        I am reminded here of a talk I went to as an undergraduate. The occasion was Clement Attlee addressing the Science Society in Newcastle upon Tyne about his experiences in the War Cabinet. In his experience, he said, the scientists they had to consult during the Second World War "were always quarrelling among themselves."
        I thought at the time, and still do, that Mr. Attlee, an arts graduate, misunderstood what science was about, and how it operated.
        Science operates on the conflict of hypotheses - the clash of ideas. Anyone who is a scientist should expect their ideas to be challenged. This has an echo in seed packet labels. One hypothesis is that the label description is what the contents are. The contrary hypothesis (there is always a contrary hypothesis) is that the label is, to some degree, wrong. This is just another way of saying, keep an open mind.
        So doubting that the contents are what the label says is not impugning the honesty, motives, or parentage of the seed donor. It is just a normal routine examination of what you have grown. We all make mistakes; I've made many myself, so expect them, and don't get hot under the collar about it. One of the more useful conventions in genetics, possibly the sole remaining relic from the age of chivalry, is that in writing down crosses the lady (female) always goes first. That is, the seed parent goes first, followed by an "x" and then the pollen (male) parent. This convention should be stuck to religiously and retained on the label, as should any breeder's number attached to the packet. Then if any puzzle arises about the parentage, you may not know who the father (pollen parent) was but you do know who the mother was and can usually make plausible deductions from that.
        One of my aims is to enable you to look at a seed list and be able to separate out certain categories to choose something which will fit your interests. I don't want you to spend a few years growing something and then realise you made a mistake. Choose wisely to start with.
        This applies whether you choose from your local chapter offerings or from the much more comprehensive list of the ARS Seed Exchange with its over 1,200 items. This latter is published early in the year and has to be requested since it is too expensive to send a copy to each member.
        First a few abbreviations:
WC: wild collected (or CW if you don't like the lavatorial implication).
OP: open pollinated, i.e., the flowers left open to insects.
HP: hand pollinated, i.e., pollen from a chosen donor has been dabbed on the stigma and some method adopted to prevent other pollen from reaching the stigma.
F1: the first generation cross between any two different plants.
F2: the offspring from selfing an F1

WC: Wild Collected Seed
This is the most reliable seed. It is more likely to produce plants like its female parent than almost any other category. Such seed is rare, especially that from Asia where certain species are being reintroduced for the first time in a century.
        Note that WC seed is not certain to reproduce the plant from which it was gathered. There are bees in the wild and when two rhododendrons flower at the same time within flying distance, natural hybrids may be formed. These have in the past caused much confusion, especially with Asia being out of bounds for much of this century, preventing observations on plants in their natural habitats. Cox and Cox in their Encyclopedia of Rhododendron Species make many comments about this problem. But even so, don't panic, WC seed is generally very reliable.

OP: Species From Gardens
This is a variable category. Because gardens, and especially botanical gardens, bring together plants from widely different geographic areas into close proximity, there is a good chance of the bees crossing the different species.
        You might assume that seed which has come from, say, the Royal Botanic Garden, Edinburgh, would be really good reliable seed because Edinburgh has one of the world's great collections of rhododendrons and the people there are top notch. Not so! Edinburgh has so many plants in such a small areas that OP species seeds from there have a higher chance of containing some hybrid seed.
        My public quarrel with the late David Leach (see JARS 42(4), Fall 1989) revolved around the above problem. David had received some of the first yakushimanum seed in North America from Exbury Gardens. He planted out a couple of hundred seedlings in his test field and selected the seven most vigorous and colourful seedlings. One of these he subsequently named 'Mist Maiden'. He maintained that 'Mist Maiden' was a fine selected plant of absolutely pure "yak" - a species which is known to be variable in the wild. I maintained that 'Mist Maiden' was a garden hybrid, and that it was its hybrid vigour that had attracted his attention in the first place.
        I last saw David Leach at the Oban convention and we talked briefly about it, but never did come to an agreement. I should say, that our "quarrel" was really just light-hearted banter; we rather enjoyed our differences.
        Some OP seed is reliable non-hybrid. This is the case for species which either flower at a time when almost nothing else is open, or belong to a small group which does not cross with other groups. Good examples are Rhododendron mucronulatum, R. schlippenbachii, R. albrechtii, R. camtschaticum, R. calophytum, and R. maximum.

HP: Seeds From Hand Pollinations
This is the most interesting category of seeds since it allows for the hybridiser to aim to produce a particular type of plant. There is, or should have been, thought applied to choosing the parents in order to emphasize a certain set of characteristics, be it colour, flower size, time of bloom, plant size, leaf characteristics, disease resistance or, God help us, double flowers.
        Sometimes you don't know what the breeder's aim was. It may have been that the two plants were just out at the same time. Among HP seed there are several categories:
1.  HP selfed species. A selfed species should produce offspring identical (or very close) to its parent. Beware though that a named clone selection never passes its name on to its seedlings, however similar. That is the Law.
2.  F1 interspecific hybrids. This is when Species A has been crossed with Species B to produce what is called the primary hybrid. These are what the early hybridisers produced. Even today there is still a use for primary hybrids. For instance, my own hobby over the past 25 years has been to make F1 hybrids between indumented dwarf species. The advantage of using species is that the F1 offspring are uniform. I have in fact found that planting out rows of seedlings reveals no variation (see JARS 39(3) Summer 1985 for an account).
3.  F2 and other hybrid generations. In contrast to the above, it is characteristic of batches of F2 seedlings that no two are identical. I remember the talk by Hachmann, the German breeder, in Vancouver, where he said that for any particular cross he raised 20,000 seedlings and might select two or three for further consideration. Don't be put off by him. This is big talk designed to impress you.
        What is true about the genetics of such crosses is that the genes are "exploded" into a myriad of combinations. It doesn't really matter whether it is a true F2 or two F2's crossed or any other way of shaking up the genes. The combinations possible among a few hundred genes are in practical terms infinite.
        This of course is the fun part of breeding. Gamblers are attracted to F2's. Your first coin (seedling) may hit the jackpot, or you may end up with empty pockets (a garden full of average pink hybrids). Come to think of it, you are better off gambling with seedlings than with coins. At least you end up with something! But, like horse racing, it is important to start with good blood stock.


Volume 53, Number 3
Summer 1999

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