Hybridizing Experiences and Recommendations
Donald L. Hardgrove
Editor's Note: Mr. Hardgrove was a Charter Member of A.R.S. as well as a Charter Member and the first President of the N. Y. Chapter founded in 1951. This lecture was delivered to the N. Y. Chapter in January 1964, as part of an Educational Series. It is intended to be recommendations to members in the East concerning hybridizing possibilities. At that time, Mr. Hardgrove gardened in Merrick, Long Island, N. Y., but in June 1964 he moved to Cooke City, Montana, and his many plants are now in the gardens of members of the New York Chapter. This is from a tape recording transcribed by Betty Hager of the New York Chapter.
What is the purpose of breeding rhododendrons? Here are twelve important reasons:
1 Good Doers
By this I mean plants that don't have to be coddled, nor given special winter protection. Breeding with good doers imparts a great deal of hardiness - a plant that is fastidious is really not worth while. Hybridity, itself, will produce good doers as a general rule unless there is an incompatibility in the cross. For example, R. williamsianum comes from a specific region in China, and in its native state is accustomed to a certain amount of rainfall, sunshine, and other specific amounts of the components of that climate. If it is planted in a different climate it will be difficult - not because it is not hardy, but because it is accustomed to receiving these specifics. If R. williamsianum was crossed with another rhododendron, you would automatically have an easier doer - it would be tempered and moderated with the plant with which it was crossed.
There are certain species which will impart floriferousness to their offspring.
3. Young Bloomers
We can cross rhododendrons and wait ten years for bloom, but this is not a good hybrid for breeding and will never be a good commercial variety. Certain species used in breeding will produce progeny which will bloom young.
4. Resistant Strains
I refer to insect resistance. I have a few very good hybrids that are always chewed to pieces. Certain species can be put into a hybrid strain which are insect resistant.
5. Foliage effects
This, more than anything else, has been neglected in breeding. It is possible to get foliage effects with all sizes and shapes of leaves, so dramatic that everyone would grow them if they never had a flower. It is possible to produce rhododendrons that will retain their foliage for four or five years, instead of dropping leaves every other year.
6. Large Flowers
Everyone loves them. All breeders try to produce them.
7. New Colors and Color Combinations
Perhaps No. 1 on the list of breeding objectives.
This can be done very easily and is very important. Certain species can be used to impart dwarfness and still not eliminate hardiness.
This is the bugaboo of all of us here in the Northeast.
10. Extended Bloom
It is possible to have good hybrids bloom in our garden from the beginning of April until the middle of July. It can be done with patience.
11. Hose-in-Hose Flowers in Rhododendrons
You have them in azaleas and it can be done in rhododendrons very easily.
This can be accomplished too, subject to linked characters. We would love a red rhododendron that was fragrant.
In starting a breeding program, it is extremely important to use the very best forms of whatever material you wish to use. There are many forms of R. catawbiense. The very best things to use in breeding are primary hybrids but there are a great many forms and you must select what is actually the best form to use. It takes just as much time and money to grow a crop of seedlings out of a poor plant as out of a good one.
In primary hybrids I made a cross of R. catawbiense var. Glass X R. fortunei, and have raised about 150 seedlings. A great many of these seedlings I would not use for breeding. To get a good clone out of the cross is the important thing. I've had flowers vary in that cross from 1½" across to almost 4" across. So make sure you get a good plant.
In selecting breeding plants, suppose you have A crossed with B (A X B) (a primary hybrid). Now you cross it with C. The resulting seedlings will vary much more markedly than your primary hybrid. It is extremely important that the genes you wish to transmit be apparent in the seedlings you are using. For example, I have a plant, R. catawbiense var. Glass X 'Fabia'. 'Fabia' is dichroanthum X griersonianum, both tender in this climate. Dichroanthum is a dwarf plant. Better forms of it are orange to orange-salmon to rather a salmon-pink. Orange and yellow genes are in it. Griersonianum is called a geranium scarlet, a really bright form of red. R. catawbiense, var. Glass is the pure white wild form of catawbiense. Now the first seedling to bloom from this cross was pink and I was glad. I thought I had it for now I had orange genes, blood red genes, and pure white genes all in one plant. There is nothing there that will give us the mud we have been getting in thousands of seedlings. Therefore I piled pollen on this plant and I used the pollen from this plant on everything in sight. But I didn't get anything good. I got some pink, some that approached red, and some white. I didn't get anything orange or orange-red and that's what I was looking for. The following year another plant of this cross bloomed which had a trace of orange in the throat, but it still wasn't what I expected out of this cross. I used this plant and it produced seedlings which were much better than the original plant but still not good enough. Then another plant came along; an orange and I used that. Now I am getting a number of orange and orange-yellow, and orange-scarlet rhododendrons. The cross itself is not as important as the individual selection.
Plan what you are breeding for. If orange color is your primary breeding objective, and you have something with 'Fabia' in it with which you want to produce an orange, make sure this particular hybrid of 'Fabia' has evident orange genes showing in the seedling, or else you are wasting your time. Crossing A x B with C x D will produce almost the ideal split up and recombination of characters. You can place enough elements in a cross of this type to come up with the point you are looking for. The percentage you get out depends upon how much you put in. If A is fully hardy and C is a fully hardy element, you will come up with much more hardiness in your resulting seedlings than if A alone had a hardy element, while B, C and D were not quite as hardy or even somewhat tender.
A noted rhododendron author once wrote that if a hardy element was not present on both sides of the cross, it would be absolutely impossible to get hardy seedlings. Both Mr. Nearing and I disputed this at the time, and we have proof. 'Beatrice Pierce' is one of Mr. Nearing's famous Ridgewood Hybrids, and there's one on the market which I call 'Virginia Hall', almost identical. Mr. Nearing's cross was R. decorum X R. griffithianum by Hardy Hybrids. One side of the cross does not have a hardy element in it. Nearing could not grow R. decorum in the open at his place in New Jersey. The plant barely stayed alive and every winter the buds blasted, and R. griffithianum is one of the most tender of all rhododendrons, strictly a greenhouse subject. R. decorum X griffithianum was crossed, I believe, with 'Kettledrum' and 'Charles Dickens', and that is the backbone of the Ridgewood Hybrids. If you took a plant of decorum X griffithianum and crossed it with R. catawbiense var. Glass, picked out the best seedling and then crossed it with a hardy hybrid, you would then get a much higher percentage of fully hardy plants.
I have tried hundreds of different species and hundreds of different hybrids. Mr. Nearing and Mr. Gable have done the same thing. I am sure it will be very helpful to know the behavior of these species and hybrids and how they react in hybrid form and what the result was of crossing them, and their value as plants for future breeding.
R. griersonianum. This, together with a few other species, is one of the most important things with which we can breed. It has a beautiful flower, close to blood red or geranium red, a little bit variable. It does not have a good habit of growth and is very tender in this climate. It has been crossed with everything in sight, but I have yet to see a primary hybrid of R. griersonianum which I would consider a good garden subject. It should be used as much as possible in breeding because it imparts two very important elements to our breeding program. First-its color is a startling clear pure red, with no trace of purple in it whatsoever. Second-it imparts to its offspring the ability to bud young (I have seen a R. griersonianum hybrid bloom when three years old). Most of these hybrids root well from cuttings.
I don't know any important hybrid that can be grown in the East that came out of R. griersonianum on a direct cross. Probably closest to growability here would be 'C. F. Raffill' and 'Vulcan' which could be used for further breeding. I used 'C. P. Raffill' and produced some beautiful seedlings. I don't know if you could bloom it in the open here-I kept mine in a cold pit-but it has genes in it which we wish to transmit for further breeding. We should try to modify this hybrid to obtain a better habit of growth and to put more hardiness in it. It has wonderful possibilities and should be exploited to its absolute utmost.
When you get into a second generation with R. griersonianum most of the tenderness seems to disappear for some unaccountable reason. The percentage of hardiness in the second generation seedlings I have grown is amazing. Don't use R. griersonianum in its pure form, use it in hybrid form. Most all crosses involving R. griersonianum and other species have already been made, and in most cases the results were seedlings inferior to either parent.
I have a cross of R. fortunei with R. griersonianum x campylocarpum. Colors here are pale pink crossed with blood red and yellow. Only 25% of the cross is R. campylocarpum, but I have a yellow seedling good enough to be named. The color is just as yellow as R. campylocarpum, the flower shape is like fortunei, but the plant itself shows no indication of griersonianum at all, not in the leaf, the flower, nor the tenderness. I mention this to show that in a cross of this type, where you have A crossed with B X C, you can completely submerge one of the elements in some of the seedlings. I named this plant 'Lemon Chiffon', a very early yellow, blooming several weeks before my deeper yellows. It blooms every year with no damage to the trusses and is hardy on Long Island.
R. auriculatum. This has limited value as it eventually grows into an enormous plant-too tall, too big, too late. We do want late flowers but when they appear in early July it is usually too hot and they don't last very long here in the East. This species has some good points, but it has so many poor points that I would not use it. The foliage is too sparse, and leaves are only held for one year-you never see a dense plant. It is too tender in itself, so it cannot impart any hardy element to speak of to the progeny. You wait ten years to see it bloom, but it does have a very fragrant and lovely tubular flower. The scent is like sweet ripe apples. You can extend the blooming season with it, but you will have to wait a long time to see bloom.
R. fictolacteum. You can get some startling foliage effects with this if you could put it in growable form here in the East. I was lucky enough to do it. R. fortunei X R. fictolacteum has produced leaves up to 16 inches long, and is a beautiful grower, and is hardy for me. But you must have room to grow it as it is one of the tree rhododendrons. These seedlings could be crossed, or could be selfed, and we could get a plant just as hardy as R. fortunei itself, and a plant that would look like R. fictolacteum.
These bloomed at a surprisingly young age. R. fortunei, itself, usually takes six or seven years and R. fictolacteum takes about twelve or fifteen or even twenty years to bloom, but most of this cross bloomed for me in about seven years. It has produced beautiful foliage plants, some with an enormous truss, eight inches across and eight inches high, almost perfectly round, with a great number of flowers in it. In other words, we got away from the drooping truss of R. fortunei and the upright truss of R. fictolacteum. The ball type truss with a great many flowers seems to be a dominant element in this cross. This would be a very promising plant for you to cross to obtain foliage effects. My plants vary in color from white to pink, but you could put something on the other side of a cross that would change that. Cross R. fortunei X fictolacteum with (C X D).
R. calophytum. This very early rhododendron, blooming about the same time as R. sutchuenense, has excellent foliage. I have a seedling of it which is very promising-a globular compact truss with a startling throat blotch. This is something that could be used to obtain early bloom, but we must get more hardiness into it. Extended bloom is very important, as we want hardy rhododendrons, in every color range, that will bloom from early April right up until the end of June-and it can be done.
R. sutchuenense. This is a little hardier than R. calophytum, but it is not quite as good as a foliage plant, nor is the flower color as good as calophytum. There are hybrids of it around, but I would prefer to breed with R. calophytum.
R. decorum. I rank this with R. griersonianum as a most important element in hybridizing. It has a large, very fragrant flower. It is a good hybridist's plant as the progeny of this species bloom very young, and the foliage is excellent. There are many reasons why R. decorum, in hybrid form, should be used. Mr. Nearing grew hundreds of seedlings of it to produce the Ridgewood Hybrids. Cross R. decorum with R. catawbiense var. Glass - you have the elements in there for an excellent breeding plant. You have full hardiness in R. catawbiense var. Glass plus floriferousness and the ability to bud young in R. decorum, as well as the ability to produce well furnished seedlings. Surprisingly, in hybrid form decorum seems to lose its tenderness. Crosses made with R. decorum on other supposedly tender plants have usually produced hardier seedlings than either parent. It is very good to use and is available crossed with other things, such as 'Jean', (decorum x griersonianum), 'Dorothea' (decorum x griffithianum), and 'Dido' (dichroanthum x decorum). But these would have to be crossed with hardier sorts. You could use a plant of either 'Virginia Hall' or 'Beatrice Pierce' (decorum x griffithianum X 'Charles Dickens'). Also available is 'Rochelle' ('Dorothea' X 'Kettledrum') and 'Gretchen' (decorum x griffithianum X 'Kettledrum')
R. discolor and R. fortunei. These are in the same group with R. decorum, all rather similar in flower. R. discolor is a very late bloomer so would be excellent in extending the bloom season, and it has a large fragrant flower. Again be sure to obtain good forms, as there are many inferior seedlings of both R. discolor and R. fortunei around of doubtful hardiness. There must be fifteen or twenty forms of R. fortunei on the market. There is one form of fortunei that is superior and I must comment on it. Years ago Mr. Nearing and Mr. Gable kept exchanging seeds of R. fortunei which had been growing out in the open in their cold locations. They would select the hardiest plants, exchange seeds, grow them again, and again select the hardiest plants and exchange seeds. After a great many years they developed a strain of R. fortunei which is definitely superior, in every way, to anything I have seen. It is a beautiful plant that never fails to winter its buds. Mr. Nearing wrote me years ago that he had fortunei in bloom after a winter that was down to fifteen degrees below zero. I have produced from this particular form of fortunei some amazingly hardy seedlings—in fact in first generation crosses it has acted as a hardier element than even R. catawbiense. Perhaps it imparts a little more hybrid vigor to the progeny than R. catawbiense.
This fortunei is a remarkably fine element to use in breeding. I crossed it with 'C. P. Raffill' and in a direct cross like that I didn't expect much. This was one of my original crosses years ago that produced so many outstanding new things in color that I was dumbfounded. I named one 'Glowing Star', a large flower, glowing rose with a salmon tint to it, and quite hardy. Of all the things I have used in rhododendron breeding, my form of R. fortunei has produced more named hybrids than anything I have used so far. It is a blush pink form, almost white.
R. orbiculare. This species I consider one of the finest to use for foliage effects, with its almost orbicular leaf, a neat dense grower. It's a bit too tender to do much with here, although it has been grown on Long Island. It certainly couldn't be considered a hardy element, but I would surely try to get plants of this in hybrid form to use to produce foliage effects. I crossed R. orbiculare with R. catawbiense var. Glass and I also crossed it with R. fortunei. Unfortunately I lost all the seedlings of my cross with fortunei but I did have six or eight plants of R. orbiculare as a pollen parent on R. catawbiense var. Glass. They are variable both in foliage and in flower, but I did have one with almost a true orbicular leaf. This would have been an excellent element to use in breeding because I can visualize a plant growing perhaps two feet high and three feet across that you couldn't even shoot a rifle through without hitting a leaf. That is possible with R. orbiculare and by incorporating some other element such as R. adenopodum which holds its foliage for four years, you may have these orbicular leaves stay on for that time and also be hardy.
R. oreodoxa. This early blooming plant interests me only because it is so extremely floriferous. The flowers are a bit droopy and it blooms a little too early (unless you wish to breed for early bloom). The hybrids I produced from R. oreodoxa are not very magical.
R. lacteum. This is said to be the yellowest of all rhododendrons as well as almost impossible to grow and I can agree as I found its hybrids rather difficult to grow, even though they were tempered by having other elements introduced into them. The hybrids I have seen from R. lacteum are lacking in vigor, the foliage is distinctly yellowish and unattractive, but the flowers had a thick, fleshy, waxy texture. It is reputed to be the yellowest of all rhododendron species and should be explored further by hybridists interested in reaching the ultimate in deep yellow.
R. forrestii var. repens. This is the so-called creeping rhododendron and could possibly give us our ideally habited dwarf red rhododendron. However it is a very difficult thing in hybridizing. I grew over 150 seedlings of 'Cathaem' (catawbiense x haematodes) X R. repens. Out of these plants I named one and will see how it behaves. The plant up until this past summer was about fifteen inches high and thirty inches across and every spring was loaded with flowers, opening a good bright clean red and fading to a less important red. Foliage was most interesting on this particular plant. But, almost all the plants of this cross were terribly subject to leaf spot and all kinds of ills. The branches died off and sometimes the entire plant died in the summer-they do not like heat. You can't put them in a much colder climate as they do not like it very cold, either. As R. repens is a very difficult species to use in breeding, I wouldn't devote much breeding time to it. Possibly the plant I selected called 'Little Flame' could be used further.
R. haematodes. This should have good possibilities. I don't believe it is as important an element in breeding for reds as is R. griersonianum, although it could give us the low compact plant we want. R. neriiflorum is a little more tender and perhaps slightly more floriferous. We can classify it almost the same as R. haematodes for breeding purposes.
R. didymum. A fine thing to use if you wish to breed for black flowers. I personally do not like the very dark flowers on the cross I made, but if you like really dark flowers, use R. didymum. It could give you a very deep red and nice dwarf plants.
R. dichroanthum. This is most important-the so-called orange rhododendron. It is not actually orange, but we can produce orange hybrids from it. It is dwarf, not terribly tender, but it cannot be grown here in its specific form. However, it is not one of the really tender elements like R. griffithianum or R. griersonianum. R. dichroanthum, in combination with other things, will give us the dwarf plants with the orange and yellow coloration that we need in rhododendrons today.
R. venator, eriogynum, kyawii and elliottii. These are extremely select plants with large vivid red flowers, but are very tender. I don't say we should not use them, for they could impart size and good red color to our hardy red hybrids, but personally I would prefer to use R. griersonianum. It is said that R. elliottii has the most magnificent scarlet red flowers of any species. Perhaps it should be explored. It blooms later in the season than R. griersonianum but its seedlings will take longer to reach blooming size.
R. adenopodum. This could be an important element to use as it is fairly hardy and can be grown here on Long Island with ease. I have a plant of it that blooms profusely year after year and it holds its foliage for four years. It makes an exceptional plant whether in flower or not. It has a felt-like indumentum on the undersurface of the leaf, and when the wind blows it is very striking. It is not hardy enough to be used as the hardy element in a cross but it is very important to use for its foliage. The flower is a nice clear pink.
R. brachycarpum. This is supposedly an extremely hardy rhododendron. It produces very small flowered hybrids, pure in color, and they will not bloom young.
R. degronianum. Closely allied to R. adenopodum, it is not as hardy. It is a nice plant but I would prefer to use R. adenopodum in hybrids.
R. smirnowii. Another supposedly hardy rhododendron that I have not had much luck with. It has a tendency to open its blossoms in the fall. It will swell its buds in the fall and then the winter kills them. My plant just does not bloom much in the spring. I have crossed it with R. haematodes and the color is a nice red, but I can't find anything to cross it with in the fall and if it imparts that character to its offspring, I would prefer not to use it.
R. catawbiense. This is the only really hardy element that I would use in a cross specifically as a hardy element. I would not use R. maximum as I have grown many R. maximum hybrid seedlings, and have crossed it in all different combinations, but I have never seen anything good come from it. The flowers are small and not a bit spectacular. I have used a plant of R. maximum X R. haematodes as a parent and grown thousands of seedlings from it. Use R. catawbiense in a hybrid form, crossed with 'Fabia' or with R. decorum. I have been referring to the Glass form particularly but the R. catawbiense var. compactum is a good element to use, too, particularly in red, as the red can overcome that purplish tint that compactum has. Compactum has a superior form of plant growth to R. catawbiense var. Glass. Since Glass has a poor habit, you must incorporate elements with it to modify that. I have a very good form of Glass from Mr. Gable - a pure white with some faint green dots in the throat, an excellent truss and it blooms like mad. However, it is a very leggy plant and this has to be bred out.
R. campylocarpum. One of the original sources of yellow, it has been crossed in every direction by many people. I have found that campylocarpum in breeding is not nearly as good an element to produce yellow as some other things available. I have used var. elatum in every direction that I could and have even used it in its specific form, and then used the primary hybrid from it, but I have yet to see anything good.
R. wardii, croceum, and litiense R. wardii and croceum impart a great deal more yellow to their offspring than does campylocarpum, from my own experience - I have used all three. I crossed R. fortunei with R. croceum and named a seedling 'Golden Star'. It is one of the deepest yellow rhododendrons. R. wardii, in combination with R. dichroanthum and my hardy form of R. fortunei has produced about six named hybrids for me, and I don't name them very easily. I have probably grown about 25,000 rhododendrons and have named about fifteen. In this cross, R. wardii X R. dichroanthum, you have yellow, and orange, combined with the hardy element in R. fortunei, and it produced every shade imaginable for me between white, pink, apricot, orange, orange-yellow, and all kinds of copper tones. These were the most amazing hybrids I have ever seen! They were variable, of course, in hardiness and form. That cross was my most successful, probably. Now, that is not the ideal cross to make, theoretically. The ideal cross would have been (R. wardii x R. dichroanthum) X R. fortunei possibly crossed with 'Golden Star' (fortunei x croceum). (R. wardii x R. dichroanthum) x R. fortunei crossed with 'Golden Star' could produce an amazing amount of yellows.
If you are interested in breeding for yellows, use R. wardii or R. croceum in hybrid form, or R. croceum, and you will have better results than with R. campylocarpum. In that same group is R. souliei itself which gives you a very interesting flower form - a flat, saucer-shaped flower that smiles at you, as R. wardii and R. croceum do. It's interesting for developing hybrids in this flower form and texture.
R. williamsianum. This is a dwarf compact grower with heart-shaped leaves. It is hard to get into bloom. We might use it with R. decorum or R. griersonianum to obtain early budding and floriferousness. A very good element to use for foliage effects would be 'Temple Belle' (R. orbiculare X R. williamsianum).
R. thomsonii, or R. arboreum. These were used to provide the red element that produced all our so-called Ironclad hardy reds. R. thomsonii was used to produce some of our hardy reds and has a large red fleshy flower. While the habit is not too good and the plant itself is not too hardy, I feel someone should start using R. thomsonii in hybrid form.
In hybrids we have two groups that have been used for breeding-the hardy hybrids and the not so hardy hybrids. I will comment on both groups.
'Atrosanguineum', 'Kettledrum', 'H. W. Sargent', 'Mrs. C. S. Sargent', 'Midsummer', and 'America' can be very valuable in breeding. I have used them all or seen the results of their use. 'Atrosanguineum' is one of the old hardy hybrids, although not as hardy as 'Charles Dickens' or 'Kettledrum'. It is a purplish-red Ironclad and has produced some good things for Mr. Gable. I have never produced anything good with it. In 1945 I crossed it with 'Coronus' ('Loderi' x 'Corona') X R. fortunei. The resulting seedling was put on 'Atrosanguineum'. I also made three other crosses: R. griersonianum X R. fortunei on 'Atrosanguineum', 'Loderi King George' on 'Atrosanguineum', and R. griersonianum x 'Armistice Day' on 'Atrosanguineum'. But I didn't get anything good. Of the group I would say 'Atrosanguineum' was of the lesser importance. It seems to impart a looseness of truss which the others do not. 'Kettledrum' and 'H. W. Sargent' produce nicer plants.
'Mrs. C. S. Sargent' I have crossed with 'Lodauric' which is 'Loderi' X R. auriculatum. One seedling bloomed. a clear pink truss, enormous in size, and with the influence of R. auriculatum it bloomed in mid-June. This is promising. 'Midsummer' is the latest of our so-called hardy hybrids. I crossed it with some pretty tender things, but the seedlings were not bud hardy. It has R. maximum in it, evident in the foliage and in the type of bloom. 'America' seems to impart poor habit to its offspring. I would prefer to use 'Charles Dickens' if you are going to use this type of rhododendron.
'Meadowbrook' ('Mrs. C. S. Sargent X 'Everestianum') is the hardy hybrid which has produced some nice seedlings for me. One is called 'Painted Star' which is 'Anita' (campylocarpum X griersonianum) X 'Meadowbrook'. 'Meadowbrook' is a sparse bloomer but it does impart to its offspring clear color and an excellent well built up pyramidal truss of frilled flowers. If you could cross it with something that had R. decorum in it, so it would bloom more profusely and at a younger age, it could produce some excellent results.
'Jean' which is decorum X griersonianum could be crossed on 'Meadowbrook'. Here again there is no hardy element on one side of the cross that produced 'Painted Star', but it is hardy. It has a complete truss, almost globular, and the flower opens with a blend of pink and yellow. As it first opens the pink is clearly defined, then after a few days, the pink starts to disappear and it becomes more yellow. The stunning part is when it fades to a primrose yellow-we have an orange-yellow flare on the upper lobe and in the center of that flare is a big maroon blotch. This rhododendron gets better as it fades! It is beautiful when it first opens and it is even more striking as it fades. Of all the ironclad hybrids I have used for breeding, 'Meadowbrook' has produced the best seedlings. It is valuable as it is a hardy pink hybrid that does not give us much purplish progeny. But, its offspring will not bud profusely.
LESS HARDY HYBRIDS
'Purple Splendour' as a parent was quite a shock to me. It will not do well for me here on Long Island. It loses many buds, and it will open about half the buds in a truss. I didn't expect very much from it but I crossed it with my hardy form of R. fortunei, and from that cross I have the most beautiful race of lavender rhododendrons that I have ever seen. Everyone seeing the plants is really amazed. It proved one thing to me-that 'Purple Splendour' has some R. griffithianum blood in it that is certainly not evident in any of the physical characters of the plant, in foliage or in flower. 'Purple Splendour' crossed with R. fortunei has given me some flowers almost five inches across in a magnificent well built up truss. These are still to be tested in really rugged weather. Beauty is there in every shade of lavender, from orchid to purple, some with an extremely spectacular blotch. I think we should try to use 'Purple Splendour' more.
'Loderi King George' is one I don't feel is particularly good. It has a big flower but the substance is not good. 'Loderi' gets wet in the rain and if the sun comes out, the flowers all turn brown. It is not hardy, not a good grower. I crossed it with some Dexter hybrids and got flowers larger than 'Loderi' but none are really hardy. One of these seedlings has a much deeper pink flower, frilled, and the plant has a low spreading habit. 'Loderi' crossed with something else and then used for breeding might be promising, but I don't think 'Loderi' in itself will produce anything magical.
'Fabia', a very good source of orange, was crossed with 'H. W. Sargent', but that cross did not produce anything worthwhile. I did get some good color but the trusses were a bit floppy. I think 'Fabia' crossed with R. catawbiense var. Glass and then crossed with something else, can give us some orange rhododendrons, and some clear bright red-orange. In that form I consider 'Fabia' the most valuable. I mentioned a cross to you of 'Anita' X R. fortunei which produced 'Lemon Chiffon'. Both 'Lemon Chiffon' and 'Painted Star' used in crosses could give us better results than using 'Anita' itself. I consider these very valuable elements as the yellow genes are certainly there in both cases.
'Diva' ('Ladybird' X R. griersonianum) was crossed with my R. fortunei and produced the best pink rhododendron I have. This I call 'Pink Symphony'. 'Diva' seems to be a promising thing to use.
'Moonstone' (williamsianum x campylocarpum) grows out in the open here in my garden (Merrick, Long Island, N.Y.), and each year it manages to open a few flowers. It blooms very early but it has genes in it we want the yellow of campylocarpum and the neat growing plant of williamsianum. I have not used 'Moonstone' enough to say it is good or not but I have the feeling it should be a very good hybrid - someone should use it.
'C. P. Raffill' (griersonianum x 'Britannia') crossed with my hardy R. fortunei produced my first really promising plant. Unfortunately I did not grow enough seedlings, but I did have a dozen. They were all clear colors, salmon rose and salmon pink. 'C.P. Raffill' should be used. It is definitely red, and probably would have to be grown in a pit. It might flower once in a while in the open.
'Mary Swaythling' (campylocarpum X fortunei), crossed with R. lacteum produced some cream colored flowers that had sickly colored foliage. The only thing noteworthy about the cross was the texture and substance of the flower, but that was not enough. Anything with R. lacteum should be exploited to the utmost, as we are starting out with the so-called deepest yellow species in existence.
'Goldsworth Yellow'. I have used it and both Mr. Gable and Mr. Nearing have used it, but I have never seen anything coming from it that had a good flower. The flowers just do not open, the flower does not expand. It is not particularly yellow, either. I wouldn't shut the door on it, but I feel there are many more important things we can use.
'Goldsworth Orange' (discolor X dichroanthum) should be good but I didn't use it as the orange genes in it are very doubtful. I had better sources of orange available such as 'Jasper' and 'Dido'. 'Jasper' (dichroanthum X 'Lady Bessborough') is one of the best orange rhododendrons I've seen for breeding. My seedlings from 'Jasper' have not bloomed yet, but it certainly has the elements there for getting orange.
'Daydream', ('Lady Bessborough' X griersonianum) I crossed with R. maximum X haematodes, but the results were very poor. I don't know whether to blame 'Daydream' or R. maximum for the results, but I still feel we should use 'Daydream' as it has very good blood in it.
'Cornish Cross' is a hybrid that has a poor habit, but it should give us good results. I had over 350 seedlings of a cross with 'Cathaem' (R. catawbiense X haematodes), but all were too tender. This could be used further. I also crossed 'Cornish Cross' with R. catawbiense var. Glass the selected seedlings of which should be very valuable for breeding purposes.
'Britannia', as well as 'Mars', when used in crosses, are supposed to give you pure colors, and no purplish seedlings. I crossed 'Britannia' with R. catawbiense var. Glass to get a pure colored form with the blood of 'Britannia' in it and also a hardier plant, and then carry it on for further breeding. The seedlings were uniformly purplish, so the entire lot was discarded.
'Cathaem'. I had a seedling out of 'Cathaem' that had a dull, but clear red flower, with no purple in it. The corollas measured 2¾" and the calyces measured 2⅞". Now this is a true hose-in-hose flower. This plant is not hardy on Long Island, but it should be definitely developed further. It is an early bloomer.
'Elizabeth' (griersonianum X repens). R. repens is very difficult and R. griersonianum is so tender that it gives us difficulties, but it certainly should be used. I have crossed it with R. catawbiense var. Glass and hope to get a deep pink to use for further breeding, or something which will definitely show the red genes, will also show the dwarf habit of R. repens, and will also bloom at an early age. We'll then breed further.
R. catawbiense var. Glass X R. discolor is an excellent late bloomer which we need as we don't have many good late hybrids. Crossed with other things we could get a race of hardy late rhododendrons, blooming at least ten days to two weeks after our present race of hardy hybrids. Again I emphasize-be sure to select the very best form for breeding!
'Vanessa' (souliei X fortunei 'Mrs. Butler') X R. griersonianum I have used, but nothing good resulted.
'Margaret Dunn' ('Fabia' X R. discolor) theoretically should give us some very good plants, but it is a bit tender and you must have hardiness on the other side of the cross.
'Moser's Maroon' has been much maligned. I like it even though it is not a particularly good grower. It seems to impart a great deal of hardiness to its offspring and it has a good deep red color. It is one of the parents of one of the finest reds that I can grow, a cross of 'C. P. Raffill' X 'Moser's Maroon'. One plant seems to be fully hardy and went through some really rough winters. It has never failed to open a full truss of flowers. The color is a little brighter than 'Mars', while the truss is much taller. The individual flower is more attractive and it certainly is a more vigorous grower. I have tried 'Mars' twice in my garden. It just doesn't do well for me.
R. catawbiense var. Glass X 'Fabia' is very promising. I have about twenty plants of it and while of no value themselves, it has the element in it we need. You have the full hardiness of Glass and the orange color and dwarf habit of R. dichroanthum. R. griersonianum gives you that startling color and ability to bud young. It is a very good element to use.
From these we can get our race of dwarf hybrids. The most important element in breeding for lepidotes is R. carolinianum. We don't have many sources of real hardiness in the lepidotes. We have R. mucronulatum (fully hardy), R. dauricum (which is supposedly the evergreen form of R. mucronulatum), R. carolinianum, and perhaps R. keiskei, although most forms are not hardy. Make sure you use a hardy form.
The greatest problem we have in breeding for lepidote rhododendrons is sterility. Both 'Ramapo' and 'Purple Gem' are sterile and we can't go any further with them. Mr. Nearing tried for years to get pollen to take on 'Ramapo' and I did too, but it is a sterile plant. It is a beautiful plant in itself but we could produce even better things from it were it fertile. R. carolinianum is the only real hope in this group, with the possible exception of R. racemosum. There are so many different strains of R. racemosum around, and many are not hardy, so be sure to use a hardy strain. Of course R. mucronulatum is fully hardy if you wish to breed for deciduous rhododendrons.
Now - let's see what we can cross. R. leucaspis. A direct cross between R. carolinianum and R. leucaspis has been made and it resulted in a hybrid called 'Starlight'. Leaves are perfectly bronzed, and it is a good foliage plant. It has pure white flowers almost two inches across, with chocolate colored anthers. That cross should definitely be done again - I'm sure it would result in a clone superior to 'Starlight'. I have hybrids from it crossed with R. racemosum but they are not too important.
R. megeratum and R. mishmiense are Boothiis and are bright yellow. I have a hybrid of R. carolinianum crossed with R. megeratum X R. mishmiense. R. carolinianum seems to cross readily with anything in the Boothii Series and the Boothiis are loaded with yellow, although some are rather tender. If we could get a hardy rhododendron out of the strain by finding a fertile seedling of R. carolinianum X R. mishmiense (or X R. megeratum) and then get a fertile seedling out of that cross, we would have an entirely new race opened up for dwarf yellow hardy rhododendrons. R. minus is almost synonymous for R. carolinianum, but it is a later blooming form and perhaps not as hardy.
R. cinnabarinum is orange, and if we can get this to cross with R. carolinianum or R. racemosum we would have something good for further breeding; we probably would have more luck in this case trying it with R. racemosum. I've tried any number of times to cross R. carolinianum with R. cinnabarinum with no success, although that doesn't say it couldn't be done. I tried any number of times to cross R. carolinianum with R. augustinii, and wasn't successful and then all of a sudden it happened. It resulted in an absolutely fabulous hybrid.
R. bullatum. I believe Mr. Amateis crossed R. racemosum by R. bullatum and it was sterile. The giants of the lepidotes are R. bullatum, ciliatum, crassum, johnstoneanum, valentinianum, nuttallii, and taggianum. R. taggianum, I understand, has been grown with a flower almost eight inches across. To get some of these big flowered things to cross with R. carolinianum, is just about impossible. I've tried it many, many times and I know Mr. Nearing and others have tried it, too. I've tried all kinds of pollen sent to me from the West Coast and from England, trying to get a cross of this type with R. carolinianum. R. ciliatum X R. dauricum produced 'Praecox' which is fertile, and you could go on from there.
In some of these crosses where we try to cross R. carolinianum with R. taggianum and can't do it, we can go in through the back door. The Boothii Series, with fine yellows in it, crosses readily with carolinianum and the Boothii Series also crosses with these large flowered ones, so why can't we take something in the Boothii Series and cross it with one of these large flowered plants, and then cross it with carolinianum? It will work - I did it. I crossed R. carolinianum with 'R. W. Rye' which is exactly what we need (chrysodoron x johnstoneanum). R. johnstoneanum is large flowered, while R. chrysodoron is definitely yellow. Unfortunately I lost the seedlings of my cross. This cross should definitely be repeated.
'Ramapo' and 'Purple Gem' (fastigiatum x carolinianum). R. fastigiatum is one of the Lapponicums, a purple color, but also in the same group we have cantabile and russatum which are much closer to blue, and we also have R. chryseum (yellow), R. flavidum (yellow), R. microleucum (white). These can be crossed with R. carolinianum. I have a plant of carolinianum X flavidum - it could give us a yellow 'Ramapo'. It has yet to bloom for me. I can't stress too strongly how important it is to produce a yellow 'Purple Gem', or a white or pink 'Ramapo'. It can be done, as this cross has been made in various directions.
R. moupinense is similar to R. leucaspis, except the flower is larger. It's not as hardy but its flower is a pure milk white. I crossed it with carolinianum and it produced a most floriferous group of plants, but I am not convinced it is hardy enough to do anything with. These plants are now three feet high, about three feet across, are perfect globes with excellent foliage, and an abundance of pure white, flat opening flowers. It is about the first thing to open in the spring, about the same time as R. mucronulatum. As far as I know they are sterile. This cross should be repeated - you'll certainly get good plants out of it, and if you get one that is fertile, you'll open up a whole new field of rhododendron breeding.
R. augustinii is the closest we have to blue in the lepidotes. I tried for years to cross carolinianum with augustinii and finally I got one to take. I don't know why - perhaps it was a different form of augustinii, or a different form of carolinianum. But even if you have failure year after year, don't stop trying - it might be just the individual. R. carolinianum X R. augustinii produced the finest blue-lavender rhododendron that I have seen in hardy form. It was loaded with flowers, but apparently it is also sterile. The flowers have a somewhat star shaped white center, so I named it 'Star Sapphire'. If this cross could be repeated and enough seedlings grown, you might even get a better one - it's worth trying.
R. hanceanum var. nanum is an extremely dwarf dense grower with lovely small trusses of creamy yellow flowers, but it is tender. I think most of us have tried it around here. I crossed it with a hardy form of R. keiskei, but the plants have not bloomed yet. If one plant is fertile we can produce a far superior form of keiskei, lower growing, more densely flowering, as hanceanum var. nanum has a great many more flowers in the truss. Once we get it into hybrid form we could possibly cross it with R. racemosum to develop a hardier strain, as keiskei readily crosses with racemosum.
R. oreotrephes is one I've grown for years and never have been successful in hybridizing. However I think it should be used as it has a perfectly lovely dwarf form, with a nice shade of lavender flowers.
In the lepidotes we lack a plant close to red, so it is difficult to breed for a dwarf red lepidote. But I remember a rhododendron grown in England some years ago that was definitely red, called 'Cinnkeys' (cinnabarinum x keysii). We could try to obtain it and use it. It is supposed to be almost as red as haematodes. This could open a red field in the lepidotes. I do doubt if 'Cinnkeys' could be grown in the open here. Try to get pollen from England.
From my years of plant breeding, I obtained exceptional results from the following crosses. Study the parentage - it might be a guide for you. R. fortunei X R. croceum produced 'Golden Star', deepest yellow I have seen. 'C. P. Raffill' X 'Moser's Maroon' produced 'Anne Hardgrove'. You could repeat this cross - it is not a hard cross to make. R. fortunei X 'Diva' produced 'Pink Symphony'. 'Meadowbrook' X (R. griersonianum X R. campylocarpum) produced 'Painted Star'. 'Cathaem' X R. repens produced 'Little Flame'. 'C. P. Raffill' X R. fortunei produced 'Radiant Star'.
R. wardii X R. dichroanthum X R. fortunei is a cross that will eventually result in six named hybrids. One I call 'Halolight'. The finest yellow of all is numbered H-62-5 now named 'Barbara Hardgrove', a larger flowered truss than the yellow rhododendron given the Preliminary Award at our New York Chapter Show at Planting Fields in 1962. It is a sister seedling. 'Donna Hardgrove' is also out of that cross. Before the bud starts to open, it is red and when the flower first opens, it is apricot-pink. Then, as the flower opens fully, it is orange. On the same truss you will have all of these three colors at once - it is a very striking effect.
R. discolor X 'Azor' produced 'June Rhapsody'. This was a case of 'Azor' not being hardy enough for this climate so I crossed it back on R. discolor. It has a distinct orange center, with a pink border, and it blooms late. I don't know how hardy it is yet.
'Fabia' X R. fortunei produced two named hybrids for me: 'Golden Glow' and 'Glow Light'. 'Glow Light' is the only rhododendron I've ever seen that I actually did a double take on. I was walking around my garden-the plant had just opened up and I didn't realize it. I walked by, looked, started to walk away - and all of a sudden I turned around quickly - why this rhododendron just "glowed." It gleamed at you with the sun striking it, and it was a soft glowing orange. It is excellent.
'C.O.D.' X R. croceum produced 'Salmon Glow' and this has an enormous truss of pure salmon flowers. Most of this cross was too tender, but this one was somewhat hardier (out of about 50 seedlings).
In the lepidotes we have: 'Starlight' (carolinianum X leucaspis), 'Star Sapphire' (carolinianum X augustinii), 'Spring Song' (keiskei pollen on racemosum X keiskei). 'Spring Song' is not startling - it was the first rhododendron I named-but it is better than R. keiskei, as it is hardier and has a better habit. R. carolinianum X R. moupinense produced a very striking plant but I did not name it as I am not convinced it is hardy enough. R. carolinianum X R. flavidum can open up a new race of dwarf rhododendrons. These crosses should be repeated. R. carolinianum X 'Silver Ray' should be repeated, also. I have only one plant, from which I expect good things. 'Silver Ray' is megeratum X mishmiense. Pollen was sent to me from England. Anything that has the Boothii Series on one side of it should be crossed with R. carolinianum.
My advice to you is first decide what you want to accomplish. Pick two or three objectives and then work on them. You must decide which species and hybrids will best fit in with what you wish to accomplish. For instance, for dwarfness, go to orbiculare or williamsianum and for foliage as well. Decide what you want to do, and then decide what you want to use to do it. Get your plants as close as you can to blooming size, or obtain pollen - breed now.
There are artificial ways of speeding up flowering. Take a piece of wire and tie it around a branch. The first year it might not do it, but the second year you can be pretty sure that it will have a bud on it. But just don't forget the wire or you will girdle the branch and it will die.
Before I close I would like to say one thing. It is a marvelous thing to have hybrid vigor in breeding, but we are breeding for beauty and there is no gene for beauty. We have to create it - we have to use our good taste to select it. Too much hybrid vigor is the one thing we should breed away from. It's useful to a certain extent, but I don't see how an extremely vigorous leggy plant can give us beauty. A plant loaded with hybrid vigor makes too much growth before it puts out a leaf - I don't like it. So let's breed for beauty.