Rhododendron Hybridizing 1972 - 2072
Maurice Sumner, San Francisco, CA
From Presentation Given at 1972 Annual Meeting
To discuss "Rhododendron Hybridizing 1972-2072" and try to predict what improvements might be expected in the next 100 years is not a particularly risky task, because I rather doubt if many of those present today will be around in the year 2072 to judge the accuracy of the predictions.
Those of us who consider rhododendrons the King of Shrubs may have a hard time acknowledging any shortcomings within the genus. In all honesty, however, the most rabid "rhodoholic" must concede that some improvement is desirable.
Most rhododendrons retain their blooms from two to four weeks. Is it possible to produce a plant that will remain in full bloom for six months of each year or one that will have two seasons of full bloom? This has been accomplished with roses.
Could a plant be developed which would retain its individual trusses for several weeks? Many orchids have this quality.
What about producing a hardy rhododendron which will come into full flower in the middle of the winter? This seems within reason as we already have Malesian rhododendrons that normally produce their best blooms in December, January and February.
In order to intelligently predict what we might expect from the rhododendron hybridizers by the year 2072, we should review the improvements that the last 100 years have produced.
What was known in 1872 about rhododendrons and about hybridizing? In an effort to get an answer to this question I examined the issues of the Gardeners Chronicle for the year 1872. Rhododendrons were scarcely mentioned. One correspondent in a letter to the editor said that for the first time he had seen
R. dalhousiae
in bloom and then asked if any one had crossed it with
R. arboreum
. The problem of crossing a lepidote and an elepidote was apparently not even known at this time - at least not to the writer of this letter.
A year before in 1871 E. S. Rand, Jr., published a book in the United States on rhododendrons. In his introduction he states: "The object of the present volume is to introduce to popular notice a class of plants which in England forms one of the most attractive ornaments of the garden. They are commonly known as "American plants" as the earliest known rhododendrons are natives of this continent. It is a singular and most unaccountable fact that these plants are but little known in cultivation in this country."
The author devotes most of the volume to American and South European species. When it comes to species from Asia he states quite frankly that he can only cite English authorities as he personally has had no experience with them. This from the author of a book on rhododendrons in 1871.
The current R. H. S. handbook lists some 1900 hybrids but only 26 of them were produced before 1900. Some of these, however, are good ones as 'Fragrantissimum' produced in 1868 - 104 years ago - and still grown extensively.
Hooker introduced both
R. fortunei
and
R. griffithianum
in the early 1850s, but it wasn't until more than 50 years later that a cross between these two species resulted in the Loderi hybrids.
In 1872 there were very few species available to hybridize and even less knowledge about the nature of inheritance. Just one hundred years ago when Darwin expounded his theories of evolution, he knew nothing about the patterns of inheritance. In 1872 he wrote:
"The laws governing inheritance are for the most part unknown. No one can say why the same peculiarity in different individuals of the same species, or in different species, is sometimes inherited and sometimes not so; why the child often reverts in certain characteristics to its grandfather or grandmother or more remote ancestor."
Ironically, the answers to the questions Darwin was seeking had been discovered six years before by an observant amateur botanist, but the patterns which inheritance follows lay unread in a dusty volume of the "Proceedings of Natural History of the Society of Brunn" (1886). Gregor Johann Mendel working in a monastery garden hybridizing sweet peas and carefully recording the results learned for the first time that there was a definite pattern which governed inheritable traits. He learned that the pattern was different in the second generation from the first. He discovered what we now know as dominant and recessive traits.
Without this discovery of one of Nature's laws, rhododendron hybridizers would not know the significance of back crossing or crossing sister seedlings.
Since the time of Darwin and Mendel an enormous amount of knowledge has been slowly accumulated over the past 100 years by scientists sitting over microscopes and with infinite patience observing the mechanism of inheritance. The difficulty of their task is realized when we remember that 5,000 cells are no larger than the dot over the letter "i". Yet the cytologist as he studied the nature and structure of the cell learned that this minute body contained the chromosomes, the genes and still smaller the molecules and enzymes and that all of these play an important part in the process of inheritance in plants as well as in animals.
Then came the electron microscope developed within the last 50 years which achieved magnification fifty times greater than the visual microscope. Whole new worlds opened up. Still further progress has resulted in recent years through a study of mutation in plants. These appeared with great infrequency, so attempts were made to induce mutations. At first alcohol, lead, and other toxic materials were used with little success. Within the last fifty years, however, fruit flies were exposed to x-rays and success beyond the dreams of the geneticists occurred. The impact of the x-ray on the arrangement of the genes produced a permanent genetic alteration that continued through subsequent generations.
The greatest advances in knowledge in this field, however, have occurred in the last few years, and we are on the verge of tremendous progress as isotopes become new tools for those seeking to solve the riddles of inheritance.
When we review the progress from 1872 to 1972, we begin to recognize the probability of learning basic new truths which may well make possible the creation of new rhododendron hybrids which seem fantastic to us today.
It would be a rash man, indeed, who would review the advances in knowledge during the last 100 years and would say that it is impossible to develop rhododendrons which would bloom the year around or that would thrive in the Midwest states of our country or that would not be adversely affected by either cold or hot temperatures.
Let us examine some areas where more knowledge is needed before progress can be expected. There is little evidence presently to indicate that inter-generic crosses with rhododendrons may succeed. It is true that Mr. Brooks here in California did successfully cross a rhododendron and a ledum and one or two other crosses between rhododendrons and other genera have been reported. In orchids and a few other plants inter-generic crosses are not uncommon. Long before the year 2072 the workers in the laboratory may well discover the block that now prevents the breeders from making these crosses. The same can be said for crosses between lepidote and elepidote rhododendrons where success has been very limited.
There has been little or no progress in crossing rhododendrons in the Vireya Section - the Malesian rhododendrons - with rhododendrons in other Series. Again we have to depend on the men working in the laboratory to discover the obstacle which prevents the successful mating of plants in these groups. The amateur hybridizer, however, may have an important contribution to make in finding a solution to this problem. I will comment on this a little later.
Well, this brings us up to the year 1972 - only 100 more years to go! I was asked to comment briefly on the direction hybridizing is taking here in the San Francisco Bay area. Because the tender varieties thrive in this climate, a number of the members of the California Chapter have been working with plants in the Maddenii and Boothii Series. The new hybrids from this area were excellently described in an article by Hadley Osborn in the A.R.S. Quarterly Bulletin of October 1968. I will refer only to a few which have appeared since that date. One of our members, Bob Scott, apparently spends many of his winter evenings planning the crosses which will lead him to his goal of small, compact, floriferous plants with good yellow flowers. He has worked largely in the Boothii Series with
R. chrysodoron
,
leucaspis
,
xanthostephanum
and in the Maddenii Series with
R. valentinianum
and the Cox form of
R. burmanicum
. All of these are yellow except
R. leucaspis
. Just a month ago I saw two of his plants blooming this season for the first time. They appear to be the best yellow lepidote rhododendrons produced to date. We are bound to hear more of them in the years ahead. They are as yet, unnamed.
Howard Kerrigan is another member of the California Chapter with considerable hybridizing experience. His principal interest is with the Azalea Series where he has made over 10,000 crosses. He has also developed some hybrids in other Series. I'll comment on two of his very fine crosses within the Maddenii Series. One between
R. johnstoneanum
and 'Saffron Queen' attracted considerable attention when it was shown at a California show. Its interest arises from the fact that it is completely different. It is a cream colored semi-double flower which looks like a double daffodil. Its stamen have turned into ten petaloids, five of which are nearly as large as the petal. It has a daintiness of form that gives it distinction. His other outstanding cross has been appropriately named 'Roy Hudson'. It is a cross between
R. nuttallii
and
R. burmanicum
. It has not yet been exhibited. The Award Committee who saw the plant was unanimous in voting to place it on the Eligibility List for a future award. It is worthy of the man after whom it is named.
The flower colors in the lepidote rhododendrons are generally white, yellow and blue and some light pinks, but very few are red or orange. My wife and I have recently become interested in trying to breed red and orange colors into a lepidote rhododendron.
R. spinuliferum
has a small tubular flower with a live vivid red color and in some forms orange flowers. It is sometimes called the "fire cracker rhododendron". If the almost iridescent red color could be carried over into larger flowers, it would be a worthwhile improvement. Lord Aberconway crossed
R. spinuliferum
with
R. moupinense
to produce 'Seta' which was given an F.C.C. award in 1962. This has a pale pink flower but the delightful red color is somewhere hidden in its genes. We crossed 'Seta' back to
R. spinuliferum
and in three years bloomed a population of plants with small tubular flowers in various shades of red, orange and pink with hardly two flowers alike. It was an interesting result, but several generations away from a large flowered luminous red lepidote. We have numerous crosses of these seedling with larger flowered whites such as
R. cubitti
, 'Forsterianum' and others and are waiting to see what comes forth. This is the excitement of hybridizing.
At this point I expected to display plants of some recent California hybrids. This is not possible because of a universal law of nature - as certain as Newton's law of gravity. It is this: "All rhododendrons are at their best one week before the show or one week after the show." The California hybrids have faithfully followed this law. We shall have to depend on some pictures which will be shown later in the conference.
So much for 1972! What can the American Rhododendron Society do now that will contribute significantly to improve rhododendrons in the year 2072? I have a proposal to suggest.
In each individual chapter there are relatively few persons carrying on a carefully planned hybridizing program. In the California Chapter of some 150 members I can name only six who have done considerable hybridizing. We know nothing about the progress in other Chapters except as an occasional article appears in the Bulletin. There is no central clearing house of information. The failures are seldom reported, but are equally important to prevent duplication of effort.
This is my proposal: that the American Rhododendron Society through its National Board of Directors establish a group within the structure of the A.R.S. of those persons having a primary interest in hybridizing. What might such a group accomplish? Let me list some possibilities.
First of all it would provide a clearing house for reporting what hybridizers all over the United States are doing: what their goals are, what their successes as well as their failures have been so that another would not have to duplicate their failures, which plants as parents best transmit superior characteristics as fine foliage. For example, the foliage on 'Noyo Chief' is as fine as anyone could desire, but who knows how many have used it as a parent or whether it transfers its green shining leaves to the first or the second generation or at all. Several may already have carried this breeding through two or three generations and already have the answers, but if I want to learn the answers I have to start at the beginning and over ten or fifteen years repeat what may already have been done. This valuable kind of information could be gathered by a questionnaire and published from time to time and preserved for future generations.
Another reason for an organization of hybridizers is this: many men have spent a lifetime crossing rhododendrons and have accumulated an enormous amount of knowledge and then they die. Their accumulated knowledge dies with them. A new hybridizer cannot start where they stopped but must start again on the lowest rung of the ladder. I'm thinking of some of the great hybridizers on the West Coast whom I knew personally who are no longer with us, Ben Nelson, Lester Brandt, Del James, Endre Ostbo and Halfdan Lem. The present and future generations suffer a great loss because we have not preserved reports of their years of experience. If we had published papers presented by each of them from time to time reporting their successes and failures and goals, the newcomer today could proceed down a straighter path with a clearer goal in sight.
An organization of hybridizers need not meet often - perhaps for an hour or so during the annual Conference of the A.R.S. A trained geneticist like Dr. August Kehr or David Leach or others might present a paper suggesting one or more long range breeding programs to reach a desired goal which members might wish to follow, and their progress could be reported from time to time. Significant papers should be published even if only in mimeograph form and distributed to all interested hybridizers so that the accumulated knowledge might not be lost. Our Quarterly Bulletin cannot adequately meet this need because such papers are of interest to only a limited number of our members.
I can get very excited when I think of what might be accomplished by such an organization. Let me suggest a few of the many projects that come to mind.
Perhaps the most significant advance in rhododendron culture would be to develop a group of plants which would thrive in the parts of the United States where they cannot now be grown. Forty miles east from where we now sit rhododendrons that thrive here will not survive under ordinary garden conditions, and this applies to most of the rest of the country. If someone with experience and knowledge of genetics could suggest a line of breeding with the goal in mind of developing rhododendrons which would thrive in hot areas of low humidity, then persons in different parts of the country might follow the suggestions and in a few years report the results. In Los Angeles rhododendrons are not happy except the Azalea Series. One rhododendron with purple flowers is an exception and is sold commercially. This might be a starting point. R. chapmanii is reported to be heat resistant in Florida. Has any work already been done with this goal in mind and with what success? Some persons may already be working with this problem, but we don't know about it.
Another area is this: enormous advances are certain to result if anyone can successfully cross a rhododendron in the Vireya section (the Malesian rhododendrons) with one in any other group. A magnificent yellow would be a certainty. Carnation fragrance and plants in full bloom in December and January could be expected. A single successful cross might supply the bridge to make this possible. This is one place where the amateur is more likely to succeed than the professional because this area has no commercial possibility. The professional is more interested in improving plants used for food such as rice, wheat and corn.
At present few persons are even experimenting in this area, and those are generally proceeding blindly. One reason is that very few Malesian rhododendrons are available, but pollen is abundant right here in San Francisco. Anyone anywhere could try his hand at getting seed from a cross to any rhododendron outside the Vireya section. As far as I am aware only four persons in California have been attempting to make such crosses and perhaps a like number in Australia plus some work in the Netherlands. This is virgin territory. At least two hundred more known species in the Vireya section remain to be brought into cultivation.
Hadley Osborn has some good reasons for thinking that it might be possible to cross a lepidote rhododendron in the Vireya section with an elepidote rhododendron in one of the other groups. He points out several reasons why this may be possible. To begin with the color range in the Vireya lepidote rhododendrons in many respects more closely approximates elepidote rhododendrons. Furthermore some Vireya species as
R. konori
and
R. leucogigas
are seven lobed with foliage similar in many respects to elepidote rhododendrons. Others have small leaves with bell-shaped or tubular red flowers and closely resemble the elepidote Neriiflorum Series. Also the scales on some as
R. konori
under powerful magnification look as much like branched hairs as like scales. These characteristics of the Malesian rhododendrons suggest the possibility that some of them may mate with elepidote rhododendrons. At least enough such crosses ought to be tried to determine whether or not success might lie down this path. Who has ever tried crossing this group with azaleas, either evergreen or deciduous? Has a single inter-generic cross ever been attempted? Many other projects might be carried out by an organization of hybridizers such as a directed mass effort to induce improvements through forcing mutations using x-rays, colchicine or other techniques.
A more creative mind than mine could propose endless avenues of investigation that amateurs might travel seeking answers now unknown. Amateurs are experimenters by nature and one just might meet with unexpected success.
Many sound reasons exist that indicate improvements in rhododendrons will occur by the year 2072 undreamed of today. Here are some of the reasons. In 1872 there were very few species to work with and only primary crosses were possible. Now we have literally hundreds of species collected in fairly recent years by Wilson, Rock, Kingdom-Ward, Forrest and others. Also, we have second and third generation hybrids to start with putting us years ahead of the early hybridizers. Furthermore many more species yet remain to be brought into cultivation with new genes. Many Asiatic species are probably undiscovered. KingdonWard stated in 1958 shortly before his death, "He would be a rash man who would proclaim that all the species of the Sino-Himalaya have been discovered. I would guess and not wildly either, that there are probably at least 50 to 100 good species and varieties still undiscovered. In fact vastly greater areas of the Sino-Himalaya than have yet been explored for plants are still virgin territory."
Another reason for forecasting great improvement is the large number of both professional and amateurs now hybridizing rhododendrons compared with mere handful in 1872. Furthermore hybrid seedlings can be brought into flower much sooner today with artificial light thus shortening the period between generations.
The soundest reason for expecting great advances in the years ahead lies in the vast store of knowledge we now have about the processes of inheritance.
None of us present today can expect with any degree of certainty to be here in the year 2072 to enjoy whatever rhododendrons may then grace the gardens of that day. Nevertheless, the hybridizers of today both amateurs and professionals alike can take great satisfaction in creating some improvements today and adding to the knowledge that will determine the rhododendrons of tomorrow.
When we speculate what the rhododendron hybridizers might develop by the year 2072, are these dreams? Let me conclude by saying that perhaps they are to some but not to those who ask as Galileo did in 1615, "Who indeed will set the bounds to human ingenuity?"