Selecting Parents for Hybridization
By B. F. Lancaster, Camas, Washington
It was quite by accident that the writer became interested in the hybridizing of rhododendrons and azaleas. One of those accident, that lay you on the shelf for along period with plenty of time to plan for the day when your state of repair might indicate a return to the production line.
At that time (1937) I had just begun to appreciate rhododendrons, in my garden. Enforced idleness gave me the opportunity to study the few books on rhododendrons I could obtain. 1 soon realized that here was a family of plants whose wide natural distribution, difference in size, type, growth, habits, as well as the varied situations to which they were native, presented almost unlimited possibilities to any one who might take the time to carefully plan a hybridizing program with definite objectives in mind.
These conclusions led me to further studies as to the parental potentialities of the various species and some of their hybrids, (F1) which were obtainable, it being the writer's opinion that the less complex the parentage the greater possibility for success. Perhaps also giving one more of a chance to call his shots. This line of thought, arrived at quite unencumbered with any particular knowledge of the laws of heredity as applied to plant breeding, proved valuable later, I believe, in helping to avoid making crosses between complicated hybrids with the usual attendant chance of a throwback to some undesirable ancestor. Concluding that a line of endeavor such as this program presented would be of never ending interest I began searching for and collecting a number of parent plants I wished to use and proceeded with my humble attempt to assist Mother Nature produce something different.
With the thought that a few result, of my experiments might be of interest to other amateurs like myself it has been suggested I record some of them. Never having had access to the rhododendron stud record until published in one of the recent A. R. S. year hooks I inadvertently made a few of the already recorded crosses. If I had known this I might have avoided making them as I feel there is much territory still unexplored in this field and anticipate improvements for many years to come.
One of my first projects was the introduction of our native azalea occidentale blood into the better forms of the deciduous types. These crosses were made using plants of occidentale parentage as the seed parent with pollen from some of the Ghent hybrids, and grown altogether in one batch. A distinct and excellent break seems to have been the result, producing large, graceful and deliciously scented flowers with up to twenty per truss, and more floriferous with each succeeding year of bloom. They are perfectly hardy, and all were fully exposed in the past extreme winter. Colors range from almost pure white to a bronze red, with many clear pinks, creamy, smoky rose, orange tints, and various combinations of these tints delightfully blended. Strangely enough there are many exact duplicates.
It might be of note that this same cross, by reversing the seed parents produced some very fine things but the percentage of above average plants was much less.
An interesting thing occurred in the only evergreen azalea breeding I have undertaken. 'Mucronatum' alba x R. pulchrum var. maxwelii. This cross produced larger flowers than either parent with shades varying from very pale orchid to deep rose, many plants appearing in the opposite cross with identical flowers but entirely different growth habits which were invariably that of the seed parents.
Most of my rhododendron breeding program was planned during those period so dear to the heart of every gardener, those seasons of the year when one because of inclement weather and long winter evenings sits by the fireside pouring over catalogs and laying plans for the ensuing season, so aptly described as "armchair gardening time."
Several important factors enter into the planning of each prospective cross; such as, hardiness, growth habits, color and form of truss, possible season of bloom, dominant or recessive traits where known, especially with parents of hybrid origin, form of the species when used as a parent, the health and vigor of the plants to be used. To stress the importance of the two last factors attention may be called to the Loderi cross, made by Sir Edmund Loder, which produced that grand group, never equaled or surpassed by the same cross made many times by others. We have been told these parents were especially selected and groomed by Sir Edmund.
It has been my practice to make reciprocal crosses, using both members as seed parents. Generally a marked difference in germination, vigor and habit will be noted in the seedlings. This practice may give a clue as to the dominant traits of the parent which carry through to a marked degree in succeeding generations. Using an excellent form of the hybrid, R. 'Fabia' (dichroanthum x griersonianum), which has proven with me a virile seed parent, with pollen from other first cross hybrids and species. I have found the growth habits of dichroanthum very predominant, with the scarlet of R. griersonianum the dominant color characteristic.
The cross R. 'Fabia' x R. 'Tally Ho' and reverse, both show this dichroanthum habit equally. R. discolor seems to have several excellent traits that carry through well. The hybrid, 'Fabia' x 'Azor', un-bloomed as yet with us, seems to show definite traits of all it's parents. The 'Fabia' x venator cross shows two distinct types of plants, both rather dwarf in habit. The 'Fabia' type having the larger leaves and flowers while the other are bushier with foliage and flowers very much like venator. The colors of both types, are intense scarlet.
R. williamsianum has proven another excellent parent, whose good traits seem to carry through successive generations, especially it's compact, very bushy, growth habits. The only hybrid of unknown parentage I have used to date as a seed parent is 'Moser's Maroon'. It's chief assets, hardiness and durability of foliage seems to carry through to it's offspring very well. I have used it with a few of the first cross R. griersonianum hybrids. Un-bloomed as yet but very interesting plants, especially the 'Moser's Maroon' x 'Tally Ho' with excellent foliage and habit. We anticipate some fine scarlets from this cross.
decorum x 'Azor', setting buds now in it's fourth year, appears very hardy with several discolor traits carrying through well. Colors should range from shell to deeper than 'Azor' with an occasional fragrance, we hope.
The production of deeper yellow hybrids presents an interesting challenge. Our attempts include various crosses of yellow species with some of the better yellow hybrids and at present have several hundred of these seedlings growing in various sizes.
The foregoing represent a few of our attempts and to you, who have all experienced the thrill of anticipation and the sight of some rare hybrid or species coming into bloom for the first time in your own garden, there waits a much greater thrill with a "tonic for living" effect, second to none, when after careful thought you select those parents and bring into bloom a new hybrid that approximate; your expectations.
I am sure most of you have ample parent material in your own garden which may be augmented with pollen from some friend's garden, to start the little adventure which, who knows, may result in a blue ribbon or other award at some future A. R. S. show or test garden.