QBARS - v24n4 A Personal Experience in Breeding Azaleas

A Personal Experience in Breeding Azaleas
Robert D. Gartrell, Wyckoff, New Jersey

My early experience in plant breeding began in Canada where I lived in the 1920's. At that time I worked with delphiniums which did very well in the Canadian climate. When I returned to the States - Northern New Jersey - I found that delphiniums were satisfactory only when grown as biennuals. Another handicap was that once a superior clone had been obtained, it could not be propagated by practical methods - cuttings. The experiment was therefore abandoned.
As I was still interested in breeding, a change of material was indicated. After several years of observation, the field was narrowed down to rhododendrons and azaleas. The latter was chosen, as azaleas give a wonderful show of bloom in the spring, and the foliage during the rest of the growing season is attractive. The growth habit is generally neat, seldom "leggy" as is the case with many rhododendron in this area. Azaleas have a long life and are easily propagated. Where large numbers of seedlings are to be grown, as is necessary in breeding experiments, they require less ground space than rhododendrons.
Next I considered two approaches as to the source of material to be used. One can work with species or one can choose to work with existing hybrids, capitalizing on other breeders' work. There are advantages in using species. There, blood lines are well established and the laws of genetics are more applicable. Hybrids have mixed parentage. In many, if not most cases, the parents are unknown, thus crosses among hybrids can produce highly unpredictable results.
Looking back, it can be seen that Joe Gable worked mostly with species while Ben Morrison used hybrids in developing the Glenn Dale series. Both were quite successful.
In the 1940's when I started working with azaleas, the number of species available was limited. Even at that time there were many hybrids, the Kurume. Kaempferi, Gables, Indian, etc. The first of the Glenn Dales were being introduced and there were a few called Chugai hybrids-these are now classed as Satsuki.
I elected to work principally with hybrids of the evergreen class. In the beginning I acquired nearly all of the available clones, growing them on, selecting the ones which appealed to me as possible parents. All told, I studied some 600 named varieties. After a few years of this, I started to make crosses. I did not work with any definite plan, merely attempting to combine the better properties of the two parents. Many excellent plants resulted, but the percentage of mediocre plants was very high. Twenty-five years later, after making some 1000 crosses and raising about 25,000 seedlings, I am beginning to learn which hybrids make good parents. Through observation and experience, the percentage of superior, hardy plants has been improved. Careful records have been kept of the results of each cross.
There are certain clones with dominant characteristics that can be expected to show in a good percentage of their offspring. For instance, Gable's 'Louise' is dominant, and appears to some degree in most of its seedlings.
The clone 'Glacier', a Glenn Dale hybrid, is interesting. Morrison stated that it came from a cross of 'Malvatica' and 'Yozakura', two quite dissimilar plants. 'Glacier' does not resemble either parent, nor is it similar to any of its sisters. I have made this cross several times, but never obtained anything approaching 'Glacier'. It was one of those fortunate breaks. What makes 'Glacier' desirable is its beautiful foliage together with large white flowers and good growth habit. It is not too hardy in this area. The good foliage and plant form seems to be dominant and is carried over in many of the seedlings resulting from crosses with other clones.
A very valuable plant for breeding is one I call 'Oakland' for my own identification. It was obtained from a wayside stand in the early 1930's. It has withstood 30° F below zero on one occasion without damage. It is undoubtedly a Kaempferi hybrid of unknown origin. It is similar to the Kaempferi hybrid 'Mary' in appearance. The flowers are single and rose pink. What makes it valuable as a parent is that it imparts hardiness to seedlings when crossed with many different clones. It is quite versatile, taking on many of the characteristics of the other parent. It has fathered plants with white as well as a wide range of colored flowers, double or single, depending on the other parent. Some of the hybrids from 'Oakland' show some evidence of Kaempferi foliage while others take on the foliage of the other parent, including that of 'Glacier' and the Japanese Satsuki.
One of my early hybrids - 'Louise Gable' x 'Tamagiku' - has been valuable in producing some degree of doubling with very good foliage and plant habit.
In recent years, I have been working with the Japanese Satsuki azaleas. These are most desirable from every standpoint as a garden plant except for one weakness-they are not reliable hardy in the Northeast. It is true that some will not like that fact that some flowers may be striped or splashed with contrasting color or that one plant may carry blooms of different colors occasionally as do some of the Glenn Dales.
The flowers of the Satsuki series are generally single, large - up to 3 ¾" - and of good substance. They are usually flat faced, not trumpet shaped, with broad petals - often with six petals instead of the usual five. The colors are mostly white or pastel shades tending to salmon pink or orange red. Only a few have the purplish red of 'Hinodegiri'. Some are strongly margined, white with a colored margin, but sometimes the coloring is reversed. All are mid to late season blooming.
The leaves are dark and glossy. In the earlier introductions, they were narrow and pointed, but later introductions are broad and rounded, much like 'Glacier'. In the South and on the Pacific Coast, they should be fully evergreen as are those I carry through the winter in a shaded cold frame. In the open here they approach being evergreen. Many of the earlier introductions are very low growing. 'Gumpo' is typical. Later ones are loco to medium height. They are nearly all dense.
I do not know who decided which plants should be classed as Satsuki. Lacking anything better, I follow the listing of Lee in his 'Azalea Book'. There is admittedly much confusion in names and descriptions. 'Gumpo' was brought in early, but nobody at the time thought of calling it a Satsuki. Later appeared a collection of azaleas called Chugai hybrids. These are now listed as Satsuki. We are indebted to the U. S. Department of Agriculture for introducing most of the Satsuki. The last collection brought in by Dr. Creech I believe to he the finest. Lee lists 168 names. I have, at various times, tried 47 of these and 37 sold to me as Satsuki but not included in those shown by Lee. Not being hardy here, many have been lost. Had I learned earlier that nearly all winter nicely in a shaded cold frame. I would be richer in Satsukis.
Practically all of my hybrids of recent years include one Satsuki parent. The object was to add hardiness without loosing the virtues of the tender plant. The Satsuki used in the crosses with best results were 'Getsutoku'. 'Heiwa', 'Amaghasa', 'Eikan', 'Shinnyo no Tsuki', and 'Tamagiku'. Two of the better ones used to improve hardiness without changing the Satsuki characteristics are 'Oakland' and 'Louise Gable'. This last may cause some degree of doubling.
As an example, a cross was made in 1962 of 'Oakland' with pollen from 'Heiwa'. Seeds were germinated on milled sphagnum moss in the green house and the following winter grown in the greenhouse bench. They were then transferred to nursery beds in the open-given no protection or mulching. The lowest temperature during the period was -10° F. Of the 41 plants set out, 37 had survived with little or no winter damage by 1969. This year I have selected 14 of this lot as being superior for growing on. They are all dense, low to medium in height, with foliage like the Satsuki with one exception. The flowers are large (3-3½ inches in size), with broad petals, flat faced. Colors range from white to shades of rose and salmon pink. Most have ruffled edges, although neither parent was ruffled. In only one case do they resemble the parent 'Oakland'.
Recently, after many years I have selected some 200 plants for growing on to determine which should be propagated and named. I expect to select another 50 plants next season. I find the matter of selection to be the most difficult part of the whole operation. I have the same problem that Ben Morrison had in selecting and naming the Glenn Dales. I suspect that he stopped because he ran out of names rather than plants. I hope to use great restraint in naming those to be commercialized. This will be quite a task as they are all so beautiful.
If and when any of these plants are available, they will be known as Robin Hill Azaleas.