Further Notes on the Dr. Joseph R. Rock
1948 Plant Expedition to the Yunnan-Tibet Border
Carl Phetteplace, M. D., Eugene, Ore.
With the rapid growth in membership that has occurred in the A.R.S. in the last 15 years or so and the consequent high proportion of new members it seems that there may be many who know little or nothing about the 1948 exploration and collecting expedition of the late Dr. Joseph Rock when he went again into the "cradle of rhododendron species." This is the term that has been used referring to the area near the Burma-China-Tibet boundaries.
Some comments and review on this project and a report on a few of the things growing in my garden that came from this expedition might be worth while for several reason. First, there have been only a few limited comments in The Bulletin about this "Rock plant material" in the last 15 years. It seems possible that the whole thing could eventually be forgotten. Second, this was the only major expedition to this area that was wholly American sponsored and therefore all of the collected material was sent to us in the United States. Third, it was the last successful significant expedition to this area and may well be the last in our time, due to the great political turmoil thereabouts which caused such bitter disappointment to Mr. Peter Cox and Mr. Hutchinson last year. Fourth, although there are several gardens that have some plants grown from the seed sent by Dr. Rock there is no complete collection growing anywhere, to my knowledge, and there has been no significant attempt made to assemble and appraise this material.
Now after 18 years we are beginning to discover that there are some very fine things in this collection and there are still many things that have yet to flower. Each year there are more and more plants that are becoming very interesting.
As a matter of review this expedition was underwritten by a syndicate of ten members of the then very young American Rhododendron Society, each subscribing an equal amount. Mr. George Grace, the first secretary of the A.R.S., was one of the prime figures in this venture and in Vol. 3, No. 2, April 1947, of The Bulletin there is a short statement about the project and with it are printed five letters to Mr. Grace, written by Dr. Rock from the field in which he was working. Here we find a list of all the numbers, given to each item sent, which included over 160 rhododendron species, with herbarium material, in addition to a quantity of primula, lilium and material from other genera. Mr. Grace and John Henny, I am told, personally took representative seeds, and all of the herbarium material, to the Royal Botanic Garden at Edinburgh, that we might have the benefit of their expert knowledge in identification. The herbarium material is still preserved at Edinburgh.
The late Mr. John Bacher was appointed custodian for distribution, which in itself was no small task.
A second article appears in The Bulletin, Vol. 4, No. 1, January 1950 titled "A Summary of Dr. Rock's 1948 Expedition to the Yunnan-Tibet border" by P. H. Brydon, which includes a list of all the numbers from 1 to 194 with identification, as far as possible at that time from the herbarium material. In most instances the Series only could be designated and only a few were named as to species. Only recently I have received a personal communication from the Regius Keeper, Dr. Harold Fletcher, at Edinburgh, stating that still some could not be identified exactly as to species, as they had not yet flowered.
Since these two reports there has been very little in our literature about what was termed by the late John Bacher as "the end of the rainbow." Dr. Carl Heller in The Bulletin, Vol. 7, No. 2, 1953, could already sense the danger of this collection being dissipated and pled for a "Bank of Rock Seedlings" so that a complete collection of these species could be assembled in one place and grown adequately to preserve, appraise and possibly distribute to other gardens. Regretfully, nothing ever came of this excellent suggestion.
There is another brief but quite significant report, for which we are indebted to Dr. Heller, on a personal interview he had with Dr. Rock not long before his death, when he was visiting the Portland Test Garden. This may be found in Vol. 7, No. 3, July 1953 of The Bulletin. Dr. Rock stated that, in many instances, they were unable to view the plants in flower in the field and mark them for collecting seed later in the year, but collected many seeds in the autumn from plants they had never seen flower. Consequently, there are instances of duplicated species under different numbers, and by the same token more than one species could well have been collected and sent under the same number. It is, therefore, obvious that a given herbarium specimen might be quite different than a plant grown from seed under that particular number. Personally, I have encountered instances of such discrepancies and doubtless others have. It must be remembered that Dr. Rock and his party experienced the most severe difficulties and handicaps, as did most explorers to these regions, in accomplishing what he did. For example, at one time they had to tear up some of their bedding and clothes to make bags in which to send the seeds.
So much for review. As a second part of this presentation it might be of some interest to report on a few of these Rock introductions growing in my garden now that 18 years have passed. In the beginning I obtained just two first year seedlings of each Rock number. My interest in Rhododendrons had only been aroused 2 or 3 years before. I had almost no knowledge of the genus and almost no place to care for such a group of small plants: A friend who was better equipped than I offered to bring them through the first year for half the plants, or one of each number. Unfortunately many did not survive and in spring I took over one of each of about one-half of the different original numbers. Despite a good deal of effort, plus fairly optimum growing conditions, I regret to say that I lost, over the next few years, a fair number of these. There are still some 50 or more growing in my garden about which a few general remarks might be of interest and by now there are several plants that could be commented on individually.
In general one might make the following comments:
For several years most of the plants grown from the Rock seed appeared quite uninteresting and even yet, after 18 years, half of those I have remaining have yet to set a bud. This, of course, establishes them as of no value to the commercial nurseryman and perhaps accounts in part why more of them are not grown.
Each year, however, there are more and more of these plants that excite the interest of those who pass through my garden and quite a number would well deserve a place in the garden even if they never flowered. Also, each year there are more and more visitors who ask if they might be permitted to take cuttings from certain plants. Most plants from this collection prefer protection from all afternoon sun and some seem to be happier with no direct sun at all. I know of none that will tolerate full sun except Rock 58, R. keleticum.
The new growth on many of these plants is one of the great delights of my garden. It begins to unfold about the time our main parade of blooms, and the Rhododendron shows, are over and gives a keen interest in the garden much longer than I ever experienced before these plants began to show their individual characteristics. Figures 10, 11, 12 and 13 are examples.
Fig.10. Rock No. 118, R. praestans
showing, the spectacular new growth.
Plant now fully 6 ft. tall but no buds as yet.
Fig. 11. Rock 140, R. coriaceum, showing
the striking white new growth. It has flowered
once, with many rather small flowers in a very
It might be of interest to mention some plants or groups in particular. There were several "Irroratum Series"; only one has flowered for me and it is not unusual except that the flower has a distinct pleasant blue tint. It deserves further watching. Cecil Smith has flowered one that is a gem which he registered under the name 'Spatter Paint.' Perhaps it is a rogue.
There are several numbers designated as R. chaetomallum. All are interesting but one especially will be mentioned later.
Rock numbers 2, 3, 38 and 100 are all in the Barbatum Series and from the herbarium material are considered to be forms of R. crinigerum. All have flowered and are fairly typical of R. crinigerum, except R. No. 3 which has a lemon yellow flower with a blotch and some of my knowledgeable visitors have considered it possibly R. bainbridgeanum. It alone has no noteworthy indumentum, while the other three not only have very interesting indumentum, ranging from almost yellow or buckskin-colored to yellowish brown, and there are many beards or bristles on the stem. All are considered very worthy by my visitors. Many want cuttings which I freely give, but no one has succeeded in establishing roots. Likewise my attempts at self pollination have not been very successful. I wonder if they are self sterile. See Figs. 12 and 13.
Fig. 12 This particular plant, Rock 38, is
the most bewhiskered of the three plants
of R. crinigerum in the garden.
Fig. 13. Rock 2, R. crinigerum,
showing flower buds.
Fig. 14. Plant of Rock 32, R. floccigerum, 5 ft. tall and
over 6 feet wide with each terminal budded. Buds are fiery
red, flowers a mixture of red and yellow.
R. No. 32 (Fig. 14) is considered R. floccigerum. It is a very beautiful compact plant about 5 feet tall and 6 feet wide. Its foliage is deep green and shiny and the stems remain red until autumn turns them brown. There is a brown, hairy indumentum along all the ribs on the under surface. Almost every terminal has a bud in recent years and just before the truss fully opens they are about golf ball-sized and a brilliant cherry red. At this point it would be a delightful Christmas tree. As the truss opens fully the color has an admixture of yellow with the red that I cannot describe. This plant in itself indeed takes us quite a way from the ordinary in rhododendron growing. Yet for the first 15 years the only reason I did not dig it up was that I was too busy to get to it.
Fig. 15. Herbarium material of this number,
Rock 14, considered, Irroratum Series, but
the leaf, with its thin tight brown indumentum,
resembles R. lacteum. Some have thought
it to be R. beesianum.
Fig. 16. Rock 48 is listed as Thomsonii Series,
but Dr. Fletcher states the herbarium specimen is
nearest R. bainbridgeanum.
R. No. 14 (Fig. 15) is listed at Edinburgh as "R. arizelum" but Dr. Fletcher comments that the herbarium specimen is "Irroratum Series." My plant certainly does not look as if it could be a relative of R. arizelum and it seems equally hard to believe it to be R. irroratum. It has rather heavy 6 inch leaves with a thin, tight, brown indumentum similar to that found on R. lacteum. The large buds are very sticky to the touch and they bloom out into a truss of 25 or more pink flowers with a deep toothed calyx. It has a tendency for some trusses to flower in autumn and again some come out so early in Spring as to get frost damage. The plant itself is quite hardy to any cold we have here. Some of my knowledgeable visitors have opined that this might be R. beesianum. This is one of several instances as mentioned above, where there seems to be variance between the seeds grown and the herbarium material. Again R. 48 (see Fig. 16) was tagged "R. bainbridgeanum." As it has grown and flowered here it is clearly R. caloxanthum. It is now a compact shrub only 18 or 20 inches tall, although it seems to be quite happy in its environment. It has a flower much like that of R. campylocarpum.
R. 112 (Fig. 17) is a very interesting shrub, very compact and sturdy, about 4 feet tall and 5 feet across. The herbarium specimen under this number is labeled "Sanguineum Series." It has a thick, deep green foliage noticeably grooved over the lateral veins on the upper surface with corresponding ridges underneath. It, too, has tight, thin, brown, lacteum-like indumentum. Some experts have guessed it might be R. traillianum. The flowers are quite white with a toothed calyx. There is a pink blotch, at the bases of the flower lobes, which shows through the calyx. I know of no other white rhododendron with a prominent calyx. There are two plants, R. 120 and R. 140, which seem to be identical and it is agreed they are R. coriaceum. These have a truss of quite a large number of small white flowers, not especially striking. The older leaves are a light green with the indumentum becoming buff colored.
Fig. 17 This plant, Rock 112 was listed as Sanguineum
Series, but experts say it is possibly R. traillianum. Plant
not 5 ft. high and 6 ft. across has white flowers with a deep
Fig. 25. Rock 73, R.
uvarifolium, originally labeled
R. niphargum, which had a
single truss of flowers in 1966.
There are two plants originally labeled R. niphargum, which I believe now is considered R. uvarifolium. One of these, R. 73, is shown in Fig. 25. Again the new growth is silvery in the juvenile state but later the rather large leaves have a buff indumentum. Both plants had a single compact truss this year made up of many small pinkish white flowers, which I think would be attractive in an old plant with many trusses.
There are several R. fulvoides in the group under different numbers and all seemingly quite similar. As they grow older they are more and more attractive because of the rich, green foliage that endures for three or more years. There has been some controversy as to whether R. fulvoides was not really one and the same as R. fulvum and that R. fulvoides should be dropped. I have two plants of R. fulvum imported from England and have seen both R. fulvum and R. fulvoides growing at Towercourt. The Rock fulvoides is typical of the ones so named at Towercourt and has a thin, fairly tight, slightly yellowish brown indumentum, quite different than the heavy brown felt of R. fulvum. A few of these plants have flowered. The truss consists of a large number of rather small pink flowers and, again, a well flowered larger plant should indeed be a very attractive garden specimen.
There were several R. eclecteums in the group. All but two have had very dull magenta-like flowers which appear in February. However, two are of a rose color that seems sufficiently promising to observe further. The others I have discarded, simply because I do not have the room to carry them on. The same can be said of 6 or 8 labeled "Heliolepis Series." All of these have bloomed. Two are outstanding and have a permanent place in my garden. The others I have had to abandon.
There is one lovely, almost pure white R. davidsonianum in the group which grows on me each year it flowers though at first I was tempted to give it up. As is the case with several of these "Rocks," I have lost the number on it.
Of special interest to my visitors is a group of plants which are listed simply as "Falconeri Series." Only one, R. 102, has flowered. The single truss this year was similar to a R. falconeri from another source that I have grown for many years, except that the flowers come out pink and later turn to cream with a blotch. All of these plants are well worth growing because of their general plant beauty, if they never flowered. Most are 5 or 6 feet tall now. Two of them have been judged by visitors as either R. praestans or R. coryphaeum, which I understand are quite similar except that the one has a pink flower and the other white. Fig. 10 shows the striking new growth on the one numbered R. 118. These two, presumed R. praestans, have a thin, tightly plastered brown indumentum in the mature state with very large leaves. The new growth, however, is quite silvery, both on the upper and lower surfaces.
The remaining 4 or 5 "Falconeri Series" are all very similar in appearance to R. 102 that has had the one truss mentioned above. I doubt if these can be R. falconeri itself. The R. falconeri from another source, which I have been assured is genuine and is now 14 feet tall, loses all of last year's leaves as soon as the current year's leaves mature, thus leaving the branches bare. Even so, the plant, now 25 years old, is majestic with a collar of large leaves around each terminal, nearly all of which are usually budded. (See Fig. 24)
Fig. 18. Rock 97, another of the
"Falconeri Series," showing the
well clothed nature of these plants while
R. falconeri itself, from a reliable source,
loses all last season's leaves as soon as
the current year's leaves are mature.
Fig. 19. Part of a plant of Rock 86,
Falconeri Series. The branch at the left
shows 4 years growth, with the 4 year
old leaves still retained.
Fig. 20 Rock 170, listed as "Falconeri
Series" showing leaf detail. It
has a heavy cinnamon indumentum.
Fig.24. This shows the "boney"
appearance of R. falconeri, with
only the current year's leaves retained,
in contrast to Rock 86, which is listed
as "Falconeri Series."
But by contrast the Rock "Falconeri Series," with their 3 or 4 years of deep green, heavily indumented leaves, have a well clothed appearance, as shown in Fig. 19 of R. 86, which shows four years of growth on the left branch with the 4-year leaves still in place. Fig. 18 shows R. 97 with luxuriant leaves covering nearly all of recent years' growth. It is 6 feet tall. R. 25 is considered to he R. arizelum at Edinburgh. Since the others, aside from the two considered R. praestans, are so similar it would suggest that we have several R. arizelums in this collection. Figure 20 shows a close-up of the leaves on R. 170. I am very impatient to see this group come into flower but wonder if I will live so long.
There are two other beautiful plants, the numbers of which I have lost. Fig. 21 shows one. I recall that it was considered "Sanguineum Series." Both of these have flowered and have very black-red flowers which appear almost two months earlier than R. didymum but look similar. At first I thought they might be R. sanguineum but Mr. Cox and Peter, who have seen them in flower say they are R. haemaleum. These plants are 5 feet tall and 6 feet across and are as well shaped as haycocks. Wet winter snows of several inches may smash them down but, come spring, they are as round and compact as is shown in Fig. 21.
Fig. 21. This is one of the Rock plants, but the
number has been lost, undoubtedly R. haemaleum.
Fig. 22. Rock 68, R. didymum, has dark green
leaves with a buff indumentum. It blooms late,
with a typical didymum flower.
There are two very fine R. didymums from the group: R. 44, which very knowledgeable people have adjudged first class, but personally I think R. 62 (Fig. 22) is quite superior because the leaves are a deeper green and are very shiny. It blooms at the same time as other didymums and has the same black-red flower.
Fig. 23. Rock 39, R. chaetomallum,
has heavy dark yellowish brown indu-
mentum beneath and a slight dusting
of farina-like indumentum above.
Flower is very deep red. 10 to 12 in a
loose truss. Plant will tolerate no direct sun.
Of the several R. chaetomallums I consider R. 39 (Fig. 23) to be superior. All have deep red flowers of great substance but R. 39 has the largest and most fleshy flower. In addition, ever since this was a small plant it has attracted my attention, because of the beautiful foliage. It retains a light white dusting on the upper surface of the leaves for a long time and the under surface has a felt-like brown indumentum. This plant is now about 3 feet tall and 4 feet wide. This group will tolerate no direct sun whatever and must have the best of drainage and plenty of moisture in order to be happy. Perhaps the most propagated and distributed of all Rock plants is R. 58, a lovely R. keleticum that grows Bonsai-like and has good-sized, pansy-like flowers when very young. It is, therefore, a good commercial item.
There are a number of other plants from this collection tucked about in different spots of my garden, some of which I have almost forgotten and certainly have neglected. Each year one or more peek out at me and make me regret that I have not found it possible to give them better care. The foregoing should be sufficient to show that Dr. Rock made a great contribution to us and possibly suggest that even now it is not too late to salvage some things that we have not treasured as much as we should have. Perhaps if I were to list the numbers that I have growing, others will be able to fill in other good things that I have lost and together we may yet be able to assemble something like Dr. Heller suggested years ago: a collection, or better yet, several collections of at least the better things that came from this great effort. Plants that do well in one garden may not do so well in another; therefore, it would he desirable to grow as many as possible of these plants in more than one place.
In addition to several plants from which I have lost the numbers, and an additional several that I have abandoned, as mentioned above, I have the following Rock numbers: 2, 3, 6, 14, 25, 26, 32, 38, 39, 44, 48, 52, 58, 62, 73, 86, 97, 100, 102, 107, 111, 112, 118, 120, 128, 140, 143, 149, 166, 170, 174, 205.
All of these I would like to save and continue to grow for many more years, and I am sure there are many others that are real treasures if properly grown over a long enough period of time to give them a chance. I am sure that there are a number of rhododendron species in this collection that are grown nowhere else in the world in cultivation and, therefore, we should make a serious effort to preserve and distribute them.
Since turning in this report on the Rock 1948 material I found that I had overlooked one previous important report, "Notes on a few of the rhododendrons collected by Dr. Rock (1948) " by Robert Bovee in "Rhododendrons 1956."
In reading these notes now nearly twenty years after the expedition, I feel that I have not added so very much as I have yet to see some of the numbers bloom. I think Mr. Bovee's report is remarkably informative considering that it was written only seven years after the Rock Expedition. I recommend that members refer to Mr. Bovee's report as it contains information that is not contained in my article. C.P.