A Further Discussion of Breeding Methods
G. G. Nearing
Mr. David G. Leach's tirade in the July Bulletin reminds me somehow of the hero of one of Stephen Leacock's Nonsense Novels, who, if memory serves, "leaped to the saddle and galloped rapidly away in all directions."
In one direction, Mr. Leach attacked the idea that when our complicated hardy hybrids are bred together, they do not produce improved forms, but breed back to what I call the inferior norm of the genus. In the interests of accuracy, I should have said subgenus, for now that the genus Azalea has been merged with Rhododendron, we have to deal with what are horticulturally two different sorts of plant. It is true that several races of the old genus Azalea, the Ghent, Mollis and Kaempferi hybrids particularly, yield a very high percentage of worthy seedlings.
Mr. Leach claims also that the catawbiense hybrids can be crossed together with like results, and cites a most extraordinary example in Cleveland, Ohio, where 3500 such seedlings bloomed and gave 175 plants quite superior to either parent, with 851 of the balance about the same quality as the parents. This is truly a contradiction of all previous experience. Mr. Leach does not say whether the 3500 plants had been selected from a much larger number, but assumes that they had not. We shall therefore follow his method of figuring percentages.
It may safely be assumed that since 1920, a million such seedlings have been raised each year by nurserymen throughout the country. Many have been sold by more or less fraudulent advertising to an unsuspecting public. Others have been grown to flowering size on countless acres such as Mr. Leach describes. Taking only the 20 millions grown before 1940, the ratio of 175 to 3500 would mean that 50,000 should have been better than R. 'Mrs. C. S. Sargent', R. 'Kettledrum', R. 'Atrosanguineum', R. 'Roseum Elegans', etc. Of these 50,000, how many have crowded their way to the top of nurserymen's lists? How many have supplanted, or even taken a place of equality with the old Waterer hybrids? Not one that I can think of. What has become of them all, Mr. Leach?
I know of one slightly inferior R. 'Kettledrum' which has been sold surreptitiously under the name of the true clone. Two or three decidedly inferior R. 'Roseum Elegans' have been mixed with the original, and the profanity they have provoked from the lips of buyers, would probably, if added together, equal the explosion of an atomic bomb. The new names now appearing on lists of hardy hybrids come mostly from Holland, and their "hardiness" is a form of humor few of us appreciate.
A likely explanation occurs to me. Nurserymen are, on the average, shall we say less naive than geneticists. Perhaps Mr. Shammarello told Mr. Leach about the parentage of the 3500 hybrids only as much as he thought it good for Mr. Leach to know. Or perhaps Mr. Shammarello himself made a mistake. Once a seed-capsule has been removed from the parent plant, there is no proof of the parentage except a few words scribbled on an envelope. Capsules can be put in the wrong envelope. Envelopes are easily mixed at thrashing time. Labels are often traded from one seed-flat to another, by accident or for mischief.
As for the famous hybrids bred from complicated hybrid parents, breeders of the past could say "None of your business" when asked for a pedigree, or could name the parents to suit himself, and so put an end to questioning. Who could ever prove the truth or untruth of so impenetrable a secret?
We do know that the hardy hybrids, those which wintered 1918 and 1935 in the East, are combinations of R. catawbiense, ponticum, caucasicum, arboreum, thomsonii, maximum and perhaps fortunei. Although R. griffithianum has been in cultivation for a century, and Anthony Waterer and others knew it well, there is no evidence that it has entered into any of the older hybrids. The breeding of these "cast iron" varieties is often spoken of as complicated, how complicated we do not know. However, we do know that many of the best were on the market in the 1860s, and must therefore have come from crosses made around 1850. Since the catawbiense hybrids as a race were hardly known previous to 1830, there was not time for more than at the most three or four generations of complication, with less than that for the admixture of the red species.
Although these older hybrids when crossed among themselves produce nothing of value except for Mr. Shammarello, they can be used to advantage with first-generation hybrids like 'Loderi', 'Angelo', 'Tallyho', 'Azor', 'May Day'. Joseph B. Gable even crossed 'Atrosanguineum' with decorum, griersonianum, and other species, but while some of the resulting plants have been named and propagated on a small scale, their chief value, as he expected, will probably be as parents for future hybrids. No doubt the reason why R. griffithianum entered so slowly into the breeding of acceptable hybrids was that in its first crosses with the hardy race, the pure species was employed. Not until other species had been crossed with it, and these first generation hybrids bred with the hardy ones, could the disastrous tenderness and early-flowering habit of R. griffithianum be segregated from its superb flower qualities. It was then that the British and Dutch nurseries came out with the magnificent varieties enumerated by Mr. Leach to prove that complicated hybrids bred together give superior plants.
Having galloped so far in this direction, Mr. Leach must also have been galloping with equal speed in an opposite one, for he proceeded to assail my idea of a second generation cross involving in total four species as a "waste of time" and a "shotgun method." This only a page or so after he had shown that the world's finest rhododendrons (hardiness not considered) were produced from crosses involving, no doubt, an ultimate six to eight parent species.
The shotgun, Mr. Leach, is a handy device. Many a hunter would curse his luck if, when a flock of ducks settled over the reeds, he found himself with a rifle in his hand. But let us imagine the geneticist sighting along his high powered rifle-at what? Does the geneticist know exactly what he wants? Could anyone know? It is all very well in the field of crop production where Mr. Leach's professors led him, and where untold thousands or geneticists are employed at public expense to dream and chew lead pencils. There the bull's eye is pounds per acre. Nothing else matters, except something that used to be called quality, and which is probably too complicated for an expert to bother about.
When the rhododendron comes along that will stagger the world of hardy horticulture, as Pink Pearl staggered the non-hardy one, what will it look like? What will be the color of its flowers? The shape of the florets? The structure of the truss? What the season of bloom? Will the leaves be broad or narrow, pointed or round? Will they droop or be held horizontal or point upward? On what date will the new leaf-growth appear? Will there be one or two or three new growths in a season? He would be a rash breeder who would answer all these questions for publication. And that is the rhododendron I want to breed. When I see it, 1 think I will know it, but I cannot write out specifications for it. Can Mr. Leach?
The shotgun method is exactly the method we want. We want to be able to look over a field of new hybrids, every one different, for how else can we hope to find the subtle harmony of all parts which spells beauty, and for which, as I said before and will say again, there is no single gene? One style of flower shape would be completely out of harmony with a pointed leaf. A ravishingly beautiful truss might appear on a bush with a gawky and ridiculous shape. The variation of a shade or two in the flower might make it all wrong for the tint of the leaf. The flowers might open a delightful color, and when the sun struck them, fade to an ugly one. Opening magnificently, the flowers might begin to fade in a day or two. Or they might open a few at a time, with no great display.
These and a thousand other considerations enter into the estimate of a beautiful plant. You cannot pin-point anything, for all qualities are relative, and the same character that would beautify one plant would spoil another.
So what do you do? I would like Mr. Leach to indicate what he intends to accomplish. He has already told us how but not what. With that rifle of his, he must have a very definite and of course marvelous goal in sight. What is it, Mr. Leach?
The rest of us take species of outstanding beauty, other species of outstanding hardiness (and of those there are lamentably few), and try to combine them by the most ultra-shotgun method, so that every possible quality will be assorted with every other in every conceivable manner. Unfortunately there are linkages which prevent certain desirable features from appearing except in combination with certain undesirable ones. With patience many of these linkages can be broken, but in our present state of knowledge, we do not even feel certain about which qualities are linked, let alone how to break the linkage.
Perhaps Mr. Leach intends to ignore all this and produce more pounds of rhododendron flowers per acre. He could swing a government bureau into action at the cost of only a billion or two dollars a year, have a thousand expert geneticists concentrate furiously on the problem with rifles and high-powered microscopes. And no doubt they would get more pounds of flowers per acre, only that and nothing more. For if they accomplished anything else at the same time, they could be accused of using shotgun methods, and surely that would make the wrist of any geneticist sting.
It must be borne in mind that when we breed rhododendrons, there is no object in producing a high percentage of offspring slightly better than the parents. A plant which is only slightly better is not worth bothering with, for the ten or fifteen years of hard work required to build up a stock of cuttings, layers or grafts, would be wasted if in the meantime someone else produced a variety superior by still another minute margin. Even without competition, it would be a long and difficult task to convince the gardening public that the hardly perceptible improvement justified uprooting an old name well established in memory and in horticultural literature, in favor of something debatably finer.
We want a notably and remarkably better plant, one which will arouse such enthusiasm that no one will question its claims to eminence. Such a plant, and for our purpose we need only a single one, is far more likely to occur in a group where the variations are extreme, including many very poor individuals, than where the majority cold to a fairly high level of excellence. Mr. Shammarello's field where 851 "were about the same quality as the parents" is not the place where an experienced breeder would look for the rhododendron of the century that will win a thousand blue ribbons.
Mr. Leach's fear that my proposed cross might result in the combination of all the bad qualities of all the parents, seems a little odd, because that is exactly what I expect and hope for. I hope for it because, if one plant did combine all the bad qualities, it would indicate that there were no linkages between the good and bad, and the prospect of another individual combining all the good qualities would be very bright indeed.