JARS v41n4 - Rhododendrons In Dixie

Rhododendrons In Dixie
Geoffrey Wakefield, Conroe, Texas

Dreams are what the world is made of we are told. Certainly, without them we would not have cars, planes, television or phones. My dream for most of the twenty odd years since coming to the USA has been to establish rhododendrons as a viable plant here on the Gulf Coast area. Always, I have said, "One day, I will have a shot at it". This year, "One day" came.
True, Tom Dodd over in Semes, Alabama has been doing wonderful work hybridizing native and deciduous azaleas. His results will give us a much wider range of colour in our gardens. Arthur Coyle was dedicated to the idea of growing rhododendrons. His work was mostly with hardy hybrids. Throughout it all, in all the conversations, debates and correspondence I have had with so many people, the one conclusion seemed to be, "You can't grow 'em here". The three main reasons for this hypothesis being; temperature, humidity, and root rot.
My thinking on rhododendrons has developed along the lines of - rhododendrons are found growing naturally from the tundra to the tropics and from the shores to the mountain tops. In heat, cold, humidity or dry, somewhere, there is some little species thriving on it. Having soldiered for six years in India, Bhutan, Assam and Burma and having seen rhododendrons growing in such areas, I know full well, even though the normal summer highs go up through the mid to upper nineties and into the hundred range here and that 60% humidity qualifies as a "dry day", it is still pretty small beer compared to what is home to rhododendrons in other areas of the world. It is just a matter of choice of the right bloodline.
Control of the root rot problems is not so easy. Rhyzoctonia and Phytophthora are both tough nuts to crack. True, modern chemical companies are working wonders but the terrible two really thrive here, on the Sun Belt where the nearest we can get to enjoying rhododendrons is our wonderful display of azaleas. But wait a moment, azaleas ARE rhododendrons for goodness sake. The Southern Indica azalea is unique to Dixie and has flourished there since before "The late unpleasantness" (The 1861-1865 unpleasantness that is), in spite of root rot, humidity and heat. So, I reasoned, if we can grow azaleas, there has to be some species or bloodline of rhododendron which will also do well.
The next stage in my thinking was - if azaleas do well here, perhaps they have some inherent or developed resistance to root rot problems. If this is so, and if I could get a rhododendron scion to grow on an azalea understock, surely that would by-pass that part of the problem. The big question being, will it work? There being only one way to find out, I called Greer Gardens in Eugene, Oregon, explained my thoughts and asked if they could bend their sales options to send me a few scions. The nursery was raided for suitable understocks, my selection being Southern Indica liners in 4" pots and older, over a year 'Fashion' (Glenn Dale) and 'Macrantha Double' (Indicum). A small "close case" was rigged up in my home greenhouse and we were ready for action. The scions arrived on Christmas Eve. Fortunately we had planned a very quiet Christmas so I was able to get them worked on over the holiday.
Numerically, the experiment has not been an overwhelming success. But, one must bear in mind, the main purpose of the experiment was to find out if in actual fact, the evergreen azalea is compatible as an understock to "true" rhododendron. The answer is a most emphatic YES! Two of the 'Prelude' scions were worked on to 'Fashion' understocks, the third on to 'Macrantha Double'. All three have taken beautifully and have made one full growth following union. One has completed a second growth, another has second growth buds lengthened to two inches preparatory to opening leaves and the third is swelling its second buds. 'Carmen' was worked on to 'Red Formosa', 4" liners. It also has made complete union and has completed one full growth. One is making second growth and the others are swelling buds preparatory to making second growth. 'Bambi' was worked on to 'Judge Solomon'. One graft took. It made secure union and has completed a full first growth. No signs so far of second growth.
The grafting method used was the English Saddle, shaping the understock to a wedge and cutting the scion to fit over it. My first problem was that it is over 20 years since I did any grafting and in that time, one's knife hand looses some of its skill. Another problem was finding a suitable tying material. Back home we always used raffia. But here, it is not available. A third problem was, we did not get the understocks into the warmth of the greenhouse in time for them to begin forwarding before the scions arrived. We also think it would have been better to receive the scions a little later. Say the end of January. Next year, I shall move my understocks into the warm greenhouse at the beginning of December. They will then be more fully active when we work the fully dormant scions on at the end of January. Another problem is, many true rhododendrons have a very thick fleshy juvenile bark. The azaleas have a very thin bark. Therefore it is not easy to get a good cambium match.
On 8th April of this year I called Mrs. Paula Cash to ask if I could join the ARS and we got to talking rhododendrons. Mentioning my work with the grafts, Mrs. Cash immediately offered to send me some scions to try at that time. It is difficult for me to fully express my gratitude for such generosity, It is through such acts that experiments such as mine are made possible. Another raid on the nursery and the scions arrived. This time, remembering my trips to Holland and Belgium, I used the Belgian Whip and Tongue method. A slanting cut is made DOWN into the understock from the side of the stem and the scion is shaped to a wedge and slipped down into this cut. The reason they used this method was that it leaves the understock with some growth ABOVE the union to draw sap up.
Unfortunately, about this time our weather went foul on us. On 2nd April we suffered the earth shattering, record breaking indignity of a FROST. This was followed by record breaking temperatures of up into the 90's. Our humidity plunged to record breaking lows of 30%. All this combined together, making it very difficult to hold the scions from making premature growth and to keep them moist. The results have not been good but I do have about twenty grafts looking very hopeful and a wealth of experience. Thank you again Mrs. Cash.
To summarize, yes, I do most certainly think it has been worthwhile. If only one scion of the entire batch had taken it would still have been worth it. It is not the numbers that matter. What matters is, we have proved that rhododendrons can be worked on to evergreen azalea understocks. We suspect that these understocks may have some acquired or inherent resistance to root rot problems. From now on, it will be a matter of the selection of the right blood lines, those from the more humid valleys between the hills of northern India, Bhutan, Burma and southwest China, I would love to try a few New Guinea species or their hybrids.
The second prerequisite is of course, PRACTICE. This summer, I shall be practicing my knife work, getting back into shape, ready for next winter.
Above all though, I need YOUR help. I need to discuss these matters with you. To correspond, to talk over the phone or meet together. I need opinions and experiences. I need cutting material from which we can root plants to test their reaction to our local conditions on their own roots. I need seed from which we can test grow some plants, again on their own roots. Then, I need scion material. If any member would care to join n this experiment, please write to me. Last and most importantly, I need your prayers and your encouragement. With them, we shall win. We shall establish, against all the odds, Rhododendrons in Dixie.