Propagation Discussed By A.R.S. Members
Several members of the American Rhododendron Society were on the program at the Annual Meeting of the International Plant Propagators' Society, Western Region, which was held in Vancouver, British Columbia, September 6-8. Rhododendrons played an important part in the program and a number of the people associated with the Society are A.R.S. members. It seems fitting, therefore, to make a brief report in the Bulletin. It is probably true that most of our members are interested in the use of rhododendrons to beautify their gardens, but there is an increasing interest in propagation. Most amateurs who become real rhododendron buffs eventually try to do some propagating, partly just to see if they can be successful and partly to increase stocks of varieties or seedlings not generally available, for their own gardens and for their friends.
The new President of the Western Section of the Plant Propagators' Society is Dr. Robert Ticknor, Secretary Treasurer of A.R.S. A.R.S. members, Bruce Briggs and Bill Curtis, each moderated a session at the September meeting and Mr. Curtis is a past President of the Society. Members giving papers will be mentioned later.
The first day of the meeting included a field trip to Vancouver Island where the first stop was made at the Dominion Experiment Station at Saanichton. There was great interest in work by Mr. J. H. Crossley who is testing growth regulators, such as Phosphon and B-9, on some twelve to fifteen rhododendron varieties each season. It is quite evident that varieties respond differently to these new materials designed to retard growth and cause relatively early and heavy flower bud formation. For instance, of the varieties being tested this year, there appeared to be no effect on 'Alice' or 'Antoon Van Welie', but the others under test all responded to some extent with 'Anna Rose Whitney' giving especially good response to the regulators.
It seems assured that by using the proper growth regulator, and by regulating temperature and length of day, certain varieties of rhododendrons can be forced to appear on the market as blooming plants practically the year around. It has been hoped that such plants, after being used as house plants during the blooming season, could be planted into the garden and make a normal flowering shrub. Experiments at Saanichton, with various plants, indicate that in some cases the growth regulators may retard growth for as much as two to four years after treatment. Plants which have bloomed very heavily, because of the treatment, are quite likely to produce less than the normal amount of flowers for two or three years after the heavy flowering season. Apparently the reaction of different varieties will be quite different and commercial use of the growth regulators will have to be on a variety basis, both as to their efficiency in producing slightly dwarfed, heavily budded plants after treatment, and as to the value of the plants for garden purposes thereafter.
The second stop was made at Mr. William Goddard's Flora-Vista Gardens. Mr. Goddard is well known in the Northwest for having a very neat and efficient, relatively small, propagating nursery, and for the very large number of new rhododendron varieties which he accumulates from various parts of the world. A brand new propagating house had been constructed and the first batch of cuttings was in the benches. All cuttings are inserted into flats of a medium worked out over the years by Mr. Goddard. The medium being used for rhododendrons was two parts perlite, two parts Styrofoam, one part vermiculite, one-half part peat. This gives a very fluffy, well-drained medium. Propagation, of course, is under mist controlled by a time clock. A large part of the stock is container grown.
The session devoted especially to rhododendrons was moderated by Mr. William Curtis of Sherwood, Oregon. Mrs. Whalley, of the J. B. Whalley Nursery, Troutdale, Oregon, spoke on "Rooting Rhododendrons in Plastic Bands." Mrs. Whalley's nursery has used electric cable bottom heat for many years, has tried various types of heating cables, but now uses the cables which builders install in floors or walls of houses for radiant heating. Mrs. Whalley does not use benches but ground beds. The cables are laid directly on a bed of sand and covered with one-half inch hardware cloth for protection and to hold the cables in place. The cables are about two to two and one-half inches apart in the beds and have automatic thermostats to control the bottom heat at about 72 or 73 degrees.
Rhododendron cuttings are put into individual plant hands, the hands being laid out and filled with peat. The peat, with no sand or perlite added, is well moistened, filled into the hands, compressed somewhat, filled up with loose peat and then the cutting stuck into the individual bands. Hormodin No. 3 or Jiffy Grow, 1 to 10, have given about the same results. The Hormodin is mixed with half Captan.
Intermittent mist is used over the beds, Flora Mist brass nozzles being fixed in plastic pipe every four feet. This runs thirty to forty-five seconds every half hour.
After the cuttings have roots, but before the roots have grown down into the cables, they are moved into flats and left on the beds with the heat turned to about fifty degrees. They are kept cool for six weeks or so and then warmed up a bit if the weather does not turn warm in the meanwhile. During this interval they are fertilized every two weeks with a soluble fertilizer.
Mrs. Whalley makes her cuttings as early as July, if customers request it, but finds that they seem to root best if taken in October, with good results extending over into November.
Mr. Ranville Hart of Mt. Vernon, Washington, discussed "Rooting In Peat Pots." He likes to root in containers and uses three inch square peat pots for standard varieties and two and a quarter inch for dwarfs. These pots are firmly filled with a mixture of fifty percent coarse sand and fifty percent peat. Bottom heat is provided by hot water pipes beneath the benches, controlled by thermostats to give seventy-five degrees bottom heat. Monarch spray nozzles, set four feet apart, provide controlled mist, ten seconds every five minutes, although they are shut off during nights and rainy days.
Mr. Hart has found the first part of November to be the most satisfactory for taking cuttings. The cuttings are given a double wound and dipped in Affy Grow, one part to ten, as they are being put into the bench. Plants are grown in the lath house for a year and then two years in the field before they are ready for sale. The fields are sprayed with Casoron and mulched with two inches of alder sawdust.
Mr. Ray Klupenger of Klupenger Nursery and Greenhouse, Inc., Aurora, Oregon, talked on "Hot Water Bottom Heat." Although most rhododendron propagators in the Northwest have used electric cable bottom heat, Klupengers have removed their cables and rely on hot water pipes beneath the benches. They found that there was considerable breakage of cables and extra labor in cleaning the benches, and as hot water heat was available, it was found to be more economical to use it for providing bottom heat. There was a little problem in locating a thermostat to get heat control until they found that a spot right over the pipes was the best. Mist is used, ten seconds on and eight minutes off, for three weeks to a month, after which the cuttings enter a weaning period with less and less water from overhead.
Mr. John Lofthouse of Vancouver, B.C., President of the Vancouver A.R.S. Chapter, discussed the use of saddle grafts in propagation of rhododendrons. An advantage of this method is that it can be used any time of year for hard to root varieties or species, or when the plant material is not in the best condition for the making of cuttings. Grafting, which used to be practiced extensively in rhododendron propagation, is now used almost entirely for special purposes, for out of season propagation, or for varieties which seem almost impossible to root. Mr. Lofthouse is a rhododendron breeder and has been able to graft scions with flower buds, received from abroad, and use them for breeding material. Some species are notably slow to bloom and they may usually be speeded up to some extent by grafting. One of these slow blooming species is R. lacteum, a species with good yellow color but rather poor plant characters.
Mr. Lofthouse likes to use a rather long cut, up to two and one-half inches, when making a cleft or saddle graft. The longer cut seems to increase the chance of success. Tongue grafts and modified side grafts are used occasionally for grafting at the beginning of the dormant season. Polyethylene bags are used to cover the completed graft so that no wax protection is needed.
"Exbury Azalea Propagation" was the topic discussed by Bob Comerford of Marion, Oregon. Mr. Comerford operates a specialized mail order retail nursery. One reason for combining azalea with rhododendron growing is that the azalea cuttings go in early in the spring and are removed in time for rhododendron cuttings to be rooted in the same benches.
A few of the Exbury azaleas are rather easy to propagate but most of the best ones are difficult.
One of the essentials with the azaleas is a safe mist system as the cuttings are so soft when they are put into the bench that if the mist should go off during the heat of the day the cuttings would be very quickly damaged. Non-fertilizing of stock plants seems to help although this can easily be carried too far.
One of the reasons why there is so much variation among the Exbury varieties, as to ease of rooting, is that the group, as a whole, has a very complex background. As many as nine different species, plus many hybrids, were used in the development of the Knap Hill type. Of course some individual varieties might have relatively few different species in their ancestry, while others would have nearly all of the many which have gone into the general breeding of the type.
Over the years Mr. Comeford has tried just about everything from the standpoint of type of propagating house, mist or plastic tent, inside or outdoors, bottom heat or no bottom heat, and many different types of media and a number of different hormones. His conclusions are essentially as follows: Take the cuttings as early in the year as possible, April if you can, so soft that they are almost limp. Take them very early in the morning from stock plants which were watered the day before. Use Jiffy Grow diluted one to twenty but do no wounding. Use coarse sand plus one-third sponge rock as a rooting medium. Have a plastic tent about three feet above the bench as a safety measure in case the mist goes off. Use mist and use electric cables for bottom heat when the nights are cool. At about ten weeks give a foliar spray of Jiffy Grow at one to twenty-five. If cuttings are very slow to root inject liquid fertilizer into the mist lines for a day.
Ted Van Veen of the Van Veen Nursery Company in Portland, spoke on "Selecting Rhododendron Cuttings." Mr. Van Veen takes his cuttings from stock plants in the nursery, some of which are twenty-five to thirty years old. The stock plants are growing in full sun with a permanent overhead sprinkler system. Stock plant flower buds are removed just as they begin to swell before blooming.
First cuttings are taken toward the end of June and normally Mr. Van Veen would like to finish by the end of July, but may put in a second small crop about the middle of September.
Rather large caliper wood is selected as such shoots usually have a number of axillary buds which will break into well branched plants with the first flush of growth in the spring. The cuttings are made long enough so that the foliage, after a reasonable amount of trimming, does not touch the rooting medium. Any flower buds present are removed at the time the cutting is made.
Mr. C. R. Johnson and Dr. A. N. Roberts of Oregon State University presented a paper on "Leaf and Apical Bud Removal as a Means of Studying the Influence of Flowering on Rooting in Rhododendron." Leaf removal studies indicate that by the time vegetative shoots of varieties like 'Pink Pearl' have reached ninety to a hundred millimeters in length, flower bud differentiation has already started and cannot be changed after that time. Apical bud removal before flower initiation increased rooting response. Apparently developing flower buds attract materials essential in rooting and so the rooting of shoots with flower buds is somewhat slower and less sure.
The topic of "Naming and Registering Plants" was discussed by J. H. Clarke of Long Beach, Washington. Propagators as well as breeders, nurserymen, and researchers are interested in the naming of plants as all need to know exactly what they are working with, and all have a vested interest in clear, concise, easily remembered, non-duplicated names. The method of registering names of rhododendrons, familiar to most A.R.S. members, was explained.
It was brought out that in the U.S.A. there are no legal requirements directly governing the naming of a plant. A breeder may use any name he wishes, subject only to the laws governing libel and liability. It is evident, of course, that re-naming an existing variety might cause financial loss to someone who had control of that variety, and redress might be sought in the courts. The question of who should name a variety seldom arises and names ordinarily are accepted by the registrar from anyone who sends them in. However, there are cases where a rhododendron has been derived from a cross made by one man, seedlings raised by another, bloomed by a third, and the plant then may be sold to a fourth party for introduction. Usually there is mutual agreement as to who should name the variety if it warrants a name, but in any case the first name published with a description is considered under the International Code of Nomenclature as being the valid name. Many varieties are named too quickly without adequate testing and so many of them fall by the wayside. On the other hand some varieties are in the trade under a number and may eventually be named by someone other than the breeder, or the introducer.
The actual naming of the variety is a highly personal thing and the breeder may let his imagination run wild. Preferably the name should be short, euphonious, distinctive and one which will appeal to the public. The name 'Pink Pearl', for instance, has been an important factor in the popularity of that rhododendron because it is a pleasing name which people readily remember.
There was considerable interest in the fact that the various rhododendron nurseries, all quite successful propagators, take their cuttings at different times of the year. It is perhaps true that the old time experienced propagator can look at a rhododendron plant and determine pretty accurately when it is at it, best potential for the rooting of cuttings. The large commercial nurseryman does not have much time to study individual shoots, or even individual varieties, and the tendency is to make most of the cuttings at what seems a reasonably favorable time. Of course there are a few varieties which experience has shown will root better if taken very early, or if taken very late, and so the horticulturally trained eye is still valuable in the propagation field.