Counter-Observations on Breeding Rhododendrons
G. G. Nearing
Under the title "Observations on Breeding Rhododendrons" David G. Leach has written some interesting and provocative suggestions from a theoretical point of view. Donald L. Hardgrove has asked me to comment on these suggestions as they apply to the practice of actual hybridizing.
At the time of Anthony Waterer, such knowledge was guarded with the utmost secrecy, in order to prevent competitors from breeding commercially successful plants. In modern America we feel that the exchange of all possible information results in all breeders producing better plants, and what is more important, stimulates public interest, to the great benefit of everybody.
I wish that I knew more about genetics. In fact I wish I knew much more about that subject than the geneticists know. They don't make it easy for us to learn, because they change their theories, often with an about-face, every few years. They have to. The results catch up with them.
However, a thorough grounding in the work of Mendel has served me so well, that I would advise every breeder to review Mendel's work until he knows it by heart. Mendel first made his experiments, then drew up a theory based on them. The reverse process so popular with geneticists today sometimes works too, but not too frequently.
By all means let us have plenty of theory. It suggests new directions for practical breeding, sometimes points out probable explanations for past failures. Even a wrong theory is better than none at all. Outstanding results have come sometimes by accident while attempting to bred an entirely different plant from what was actually produced.
One of the disadvantages of overemphasis on theory is a tendency to build up blindness to the facts. The facts, in this case, are plants. Breeders, particularly in Britain, have set out to produce a pure shade of red. Concentrating their attention on this one quality alone, they have given fantastic awards to plants which, it is true, flower in this shade, but have little else to recommend them. Shall we do the same in America?
If we want a pure shade of red, and care nothing about what comes with it, our best route is to the paint shop. We can find there the purest imaginable shade. We can use it on house and garage, and perhaps decorate a few rocks with it. How the neighbors would stare! On second thought, what we want is not this single quality of red but a beautiful plant bearing abundant and beautiful flowers of the red shade.
There is no gene for beauty. Beauty comes when you least expect it, sometimes from combinations of unlovely things. Science and theory have no comprehension of beauty, because science cannot explain it. Beauty lies in the province of art. How then shall we breed a beautiful plant?
The most likely way is to take a beautiful plant and try to improve it, or take two beautiful plants and try to combine their elements of beauty, while eliminating whatever undesirable qualities they possess. This last method is the one Mr. Leach has in mind, and to which he applies his theories.
"There has come into being among rhododendron breeders, he writes, "a philosophy of arranging crosses which, from a theoretical standpoint, seems to be wholly without support." Philosophies and theories (Is there any difference here?) need support from results rather than from other theories. Some theories need support very badly.
Mr. Leach then advocates the crossing of two species, later inbreeding the progeny, or if the plant will not accept its own pollen, crossing it with a sister seedling. This we have often tried, and sometimes it succeeds, but usually not.
"There is entirely too much crossbreeding among rhododendrons, in my opinion," Mr. Leach writes, "and the variability which results from this cross-breeding is seldom used to advantage by the hybridist because he fails to inbreed for his next generation."
Well, one man's opinion is as good as another's, sometimes even better, as F. P. A. used to say. In practice, inbreeding in the second generation does not commonly give as much variation as one would hope for or expect. Rhododendrons tend to breed toward what I like to call the norm of the genus, which is something half way between R. ponticum and nothing at all. The results of inbreeding and of crossing complicated hybrids, tend to approach this norm.
Beauty is the quality that wins ribbons, and science does not tell us how to achieve it. The best we can do is shake up the qualities of more than one beautiful species in Mendel's hat, and see what we can draw out of it, but we must be sure to do the best possible job of shaking up, and in practical experience, Mr. Leach's does not appear to be the best method.
Furthermore, we must also include the indispensable quality of hardiness. With a very few hardy species we have been crossing a great number of superior non-hardy ones. If now each of these interspecific hybrids is selfed, we will have a series of intermediates between them and the inferior norm of the genus. (This norm has no scientific standing, isn't even a fact, but rather a tendency.) In other words, we have found that most of our trouble in raising thousands of plants is wasted.
What actually happens with the hybridist? Take an example. In 1935 I moved my nursery to Ridgewood, N. J., and while moving had a potted plant labeled decorum x auklandii come into bloom. I had no time to spare and little pollen. Usually I carry a tin box with forceps and small scissors and a number of envelopes containing whatever pollen I have been able to collect. During the moving I had collected none. To self this hybrid would have been futile, for not a single plant of the offspring would have proved hardy. So I used pollen of the red hybrids R. 'Charles Dickens', R. 'Chas. Bagley', and R. 'Kettledrum', expecting nothing in particular. The seed parent contributed large and beautiful flowers and fragrance, the pollen parents hardiness and red color.
The astonishing result was a batch of fully hardy plants with fine, disease free foliage much like that of R. decorum. The flowers too in the best forms were about the size and shape of decorum, some of them fragrant, many in remarkable shades of bright rose, some with a conspicuous central blotch of maroon. Mr. Leach, seeing them in 1950, declared them equal to anything he had seen in a week's tour of the East, including many of the Dexter hybrids. The hardiest is 'Beatrice Pierce'. Two others are being propagated.
These Ridgewood hybrids were by far the best cross I ever made, excepting the dwarfs, and were not the result of any plan, but mere force of circumstances. So to a lesser degree are many of the crosses made by many of us. A plant comes into flower. What pollen should be used on it? Surely some pollen we have or can secure. The stigmas will wait a few days if the flowers were emasculated just before opening. (Goodbye hopes of a color slide.) Suppose the plant is 'May Day' (haematodes x griersonianum). Here is a parentage of very fine red color, good flower form, poor growth habit, sparse foliage and no hardiness. How are we to shake Mendel's hat so that we can draw out a beautiful hardy plant. Somewhere in the pollen parent must be the missing qualities of hardiness, dense foliage and good growth habit. And since the red color is the outstanding merit of the seed parent, we should also try for a fine red. Experience teaches that if we want a red flower, as many as possible of the parents should be red. Gable's red catawbiense might fill all these requirements, as might catawbiense x haematodes. We try them and hope.
That is the practical way to breed rhododendrons, to use the best of what you have or can procure. Several types of cross give promising results. In the Rhododendron Stud Book the list is overwhelmingly of first crosses between species, and the overwhelming majority of them have received no awards. Of those with awards, virtually none are hardy. In a second large group, the first cross between species has been crossed again with a third species. Here the proportion of awards is much larger. In a few cases, the second type of cross has been backcrossed on one of the species, or has been crossed with a fourth species. In still fewer instances hybrids have been crossed together, and twelve of these have won awards.
But the Stud Book includes few plants fit for general cultivation, even in England. The rhododendrons actually planted and generally popular are mostly bred in the nurseries of England and Holland, and though their parentage is in most cases carefully concealed, sufficient detail has leaked out to guide those who wish to be guided. In 1850 Standish and Noble actually published the pedigrees of some of the older hybrids.
A quotation from this publication may throw some light on the fear of degeneration from selfing, which Mr. Leach mentions and considers of little importance: "We find that...breeding 'in and in' produces weak and deteriorated constitutions. We have a remarkable instance of this in a batch of hybrids raised from R. 'Caucasicum Album' (that being a hybrid), fertilized by its own pollen. The plants are extremely dwarf with variegated foliage. So dwarf are they that many of them bore eight or ten flower-buds when only from 4 to 6 inches high and four years old. Flowers produced by these dwarfs were again fertilized by their own pollen, and although seeds were produced and these germinated, the plants could not be kept alive, but after various durations of existence, from two to eighteen months, they finally disappeared." Modern scientists might say "died from unknown causes" and so cling to their theories.
Mr. Leach has an ingenious suggestion for remedying any degeneration due to inbreeding. He would have us breed the plants out again, analogous in reverse to the wondrous wise man who fell into the bramble bush. For anyone having several lifetimes to spare, I would recommend this method.
My own feeling, after years of breeding during which I compared notes with Joseph B. Gable, Charles O. Dexter, Donald L. Hardgrove, and anyone else who would compare notes with me, is that the ideal cross to shake the Mendelian hat is one between two primary hybrids, as (dichroanthum x griersonianum) X (griffithianum x griersonianum) 'Radiant Morn' A.M. 1951. Here if one of the griersonianum could be changed to catawbiense, we should have a good formula for a hardy rhododendron of high quality, though it might be necessary to grow a thousand or so before the good one appeared.
The use of hardy hybrids of unknown parentage sometimes gives good results when they are crossed with primary hybrids between species, seldom when they are crossed with each other. Gable has made extensive use of R. 'Atrosanguineum', showing that it has good possibilities as a parent. 'Charles Dickens' on the other hand tends to pass on to its progeny a stubborn refusal to propagate. 'Boule de Neige', usually a poor parent, has produced a magnificent plant with pollen of 'Loderi', though the record in this case is somewhat doubtful.
Back-crossing is useful in many instances. A little detective thinking arrives at the conclusion that one reason for the popularity of this method is the virtual certainty that the breeder has the plant to cross back on, and may not have anything more desirable. Standish and Noble revealed in 1850 that catawbiense x arboreum. back crossed with catawbiense produced R. 'Blandyanum', R. 'Towardii', R. 'Meteor', R. 'Elegans', R. 'Nobleanum' bicolor and R. 'Pulchellum', all of which had some success in their day, while (maximum x ponticum) X (catawbiense x arboreum) gave 'Standishii', 'Mrs. Loudon', 'Picturatum', 'Vivid', 'Captivation', 'Raeanum', none of which made much impression on public attention. Here we can see that arboreum and catawbiense are more ornamental than either maximum or ponticum. The method here is less important than the quality of the original parents.
Hybridizing consumes a great deal of time which sometimes can be saved by a moment's thought. Small flowers like those of R. racemosum are particularly difficult to emasculate, and even after the most painstaking care are usually contaminated. Every year I make crosses on racemosum, and every year raise some seedlings of the species. Long ago I learned not to make any attempt at emasculation. A little of the foreign pollen on the stigma usually gives some seeds of the cross, while natural pollination furnishes plenty of seeds of the species. The seedlings are separated at the age of a year or two.
Open pollination is sometimes as useful as the most careful crossing. When Joseph B. Gable's 'Conestoga' (carolinianum X racemosum) proved unsatisfactory in northern New Jersey, I was determined to produce the same thing in hardy form. This was a group hybrid. Mr. Gable had a row of the seedlings, all much alike. They could have been selfed or crossed with one another, but when I didn't know which was the better method, or whether to back-cross, I simply asked Mr. Gable to send me open pollinated seed. The bees would have selfed, crossed and back-crossed, and perhaps introduced another species or two-all without any effort on our part. Nearly all the seedlings proved worthless, but eventually 'Windbeam' and 'Wyanokie', which are now being propagated, came up to the specifications.
Here is a problem which theorists would be slow to solve. I had a couple of buds on R. discolor and wanted to make several crosses, the most important with R. smirnowii. At the same time I needed Kodachrome slides of the flowers, so did not wish to emasculate. This form of discolor takes its own pollen in preference to almost any other, but if enough of the foreign pollen is placed on the stigma, so that it is completely covered, there is little likelihood that other pollen will reach it in any quantity. Unfortunately the late bloom on smirnowii furnished little pollen, and it was already old, therefore would be slow to germinate, and with a very long style to travel down. I took the Kodachromes and got the seed, satisfied that I would want to grow seedlings of discolor in any case. But the selfed seeds of discolor and the crossed seeds of discolor X smirnowii, though mixed in the same capsule, are now in separate packets, ready for sowing.
I hope every theorist who reads this bas already arrived at the method by which the seeds were separated. The seeds of discolor are straw-colored to whitish, with a wide, papery wing all around, those of Smirnowii dark brown, wingless, and less than half the size. In the capsule were typical whitish discolor seeds and a few' blackish with a much smaller wing. It took only a few moments with a knife point to pull the hybrid seeds from the mass of those uncrossed.
Most of us like to plan in advance what crosses we are going to make when the flower buds open. All such plans should be tentative. The flowers may not open at all, but may be destroyed by frost, eaten by squirrels or broken off by accident. If unsheltered, they may open during a rainy period so extended that pollen will not remain on the stigma at any time. They may be without pollen and even sometimes without pistil. We do not know exactly when they will open, or how long the pollen intended for them will keep viable.
The most practical method, then is to keep all available pollen and date it. When a flower opens, sit down beside it, sort out the pollen that could possibly be appropriate, then think, Except in preliminary crosses, there should be at least one fully (not borderline) hardy original parent. When a recessive color, such as red, yellow or orange is wanted, as many as possible of the original parents must have that color. At least one of the original parents should have attractive foliage and growth habit. In other words, unless every quality needed for a first class hybrid is somewhere in the parentage, there is no use making the cross.
Since the hardiest species are not the most beautiful, should we use a majority of hardy parentage, in the hope of arriving at extreme hardiness, or a majority of beautiful ones, satisfied that a few of the offspring at least will be hardy? That is a decision each must make for himself, but the second alternative has a distinct advantage. The great problem of the hybridist is finding space enough and time enough to care for the young plants. If the majority parentage is hardy, the minority beautiful, a great many of the plants will survive to maturity, and most of them will have to be thrown away. If the majority parentage is beautiful only a few will survive, requiring little space and little care, while approximately the same small proportion will eventually prove worth keeping.
Such lines of thought applied to each cross ought to bring a measure of success, but by all means read everything available, know your original species as intimately as possible, and keep records. And above all be ready to experiment.