Species Rhododendrons
Mrs. E. J. Greig, Royston, B.C.
An illustrated talk given at the Portland Chapter Meeting, November 19, 1964.
The first rhododendron to be introduced into England is said to have been
R. hirsutum
in 1600, followed by
R. ferrugineum
nearly 100 years later.
R. ponticum
was introduced from Gibraltar in 1763. In the early 1800's there were only 15 spp. including azaleas in cultivation in England, chief among them being
R. ponticum
and
R. caucasicum
from Asia Minor and the Caucasus,
R. catawbiense
,
R. maximum
and
R. calendulaceum
from North America.
In 1810 Hamilton introduced
R. arboreum
from the Himalayas. Immediately following him Wallich and Griffiths went into the Himalayan area, and Sir Joseph Hooker in 1847. These men introduced many of the Himalayan species now in cultivation. Some of the actual plants from their seed collections are still alive in the West of Scotland, Cornwall, and Ireland. They were all too tender for anywhere but the warmest areas.
In the last two decades of the 18th century the French missionaries, Pere David, Delavaye and Frages, and Professor Augustin Henry began to arouse interest in the Chinese species by botanical specimens sent back to Paris, plus a little seed. Fortune had been in China earlier and, in 1855, had introduced
R. fortunei
, but the Royal Horticultural Society which first sent him to China and later the East India Tea Company had given him very specific instructions which he had to follow. Then, too, conditions were such that Fortune could collect seeds and specimen only a few miles from the Treaty Ports. However,
R. fortunei
was the parent in much hybridization, besides being in itself a very fine and extremely hardy plant.
In 1899, the old nursery firm of Veitch of Chelsea sent E. H. Wilson to Hupeh and Szechuan. Later Wilson was sent out again by the Arnold Arboretum.
First of the Garden Syndicates
In 1904-06, George Forrest was sent to Yunnan by a small group of rich and enthusiastic gardeners. Most of the collectors since that time have been entirely, or to a considerable degree, financed by such garden syndicates, who in return for their support shared in the seeds and plants collected. Over the years the subscribers have become more numerous with much smaller outlay of money per subscriber.
The men who contributed most to the great harvest of rhododendrons and other plants new to gardens were: Forrest from 1904 until his death in China in 1931 collected in Burma-Yunnan, Szechuan; Farrer, from 1914 until his death in upper Burma; Rock from 1924-1932 and 1950; Kingdon Ward from 1923-1963 went into most of the above areas plus Assam and Bhutan; Ludlow and Sherriff from 1933-19-19 went to Bhutan, Tibet and Kashmir; Pollunin, Sykes, Lowndes and others in 1949, 1950, 1952 and 1956, went to Nepal.
As we are so far growing very few of the "Javanicums" and have never seen any of them in cultivation except a few very depressed seedlings, I can say nothing about them except that the few colored slides we have seen look very interesting, indeed. However, all the information at our disposal is Dr. Sleumer's "The Genus Rhododendron in Malaysia" which he kindly sent us several years ago and, that, like old "Species of Rhododendrons" is strictly botanical - so I regretfully leave them and return to more familiar plants.
Wilson's first collections were named at Kew by the collector and Dr. Hemsley. The new species described in the Kew bulletin and his collections on behalf of the Arnold Arboretum were enumerated in Plantae Wilsonae. Much of the material in J. C. Millais' lovely volumes is the result of the latter collections.
The Series Concept
Then Balfour, Tagg and Wright Smith took a hand to try to bring some order into the vast amount of new rhododendrons pouring in. They classified and described most of Forrest's collections and at the same time laid the foundations for the genus as we know it today. Balfour selected an outstanding species as the nucleus of a group, gave it a serial name, and included in each of these series those species which appeared to be more or less related. Balfour's scheme was adopted by the Rhododendron Society and a small handbook was issued by J. C. Williams of Caerhays Castle, Cornwall, with a list of the Series in alphabetical order and the names assigned by Balfour. Eventually these were defined; keys to the species provided: and each species described in the Rhododendron Society's "Species of Rhododendrons" published in 1930 and written by Alfred Rehder, Azalea section, Tagg elepidote, spp. and J. Hutchinson lepidote spp. It is from an article in the first of the R. H. S.'s Rhododendron Yearbooks that I am more or less quoting. The article is "Evolution and Classification of Rhododendrons" by Mr. Hutchinson (1946).
Quoting again, this time from the introduction to that first "Species of Rhododendron...each series must be considered an open question. The arrangement is essentially tentative" and later "there are many problems in this record quite unsolved or but half solved. Aid us to solve them." J. B. Stevenson is the author. Since that time new species have been added occasionally and a certain amount of revision has taken place with, no doubt, more to follow.
Series Revisions
In the booklet, "Notes From The Royal Botanic Garden," Edinburgh, 1940, John McQueen Cowan dealt with the Sanguineum Alliance. He rearranged, combined and deleted various species and sub-species, but to most of us he still left it a most confused group of what I personally think is possibly a very few spp. and many hybrids. In the early days most collectors stoutly maintained that rhododendrons did not hybridize in the wild, but towards the end of his life, Captain Kingdon Ward came to the conclusion that they did hybridize where opportunity offered, which must have been quite frequently, if not as easily as in our gardens. Sanguineums are distributed throughout Western China, and into Burma and Tibet.
In 1947 Dr. Cowan and H. H. Davidian began a series of revisions in the Royal Horticultural Society's Yearbooks with a "Review of the Anthopogon alliance," combining with that the previously separate Cephalanthum series.
In 1949 a review of the Campanulatum series and the Fulvum series was published. No major changes were made in the former series. The two botanists felt that in such a diverse and almost unrelated group nothing could be done until the interrelationships among the Arboreum, Lacteum and Taliense series were explored as well. That has not been done yet. I think the Fulvum series was reduced from five species to two with not even varietal names to commemorate the vanished species.
The Thomsonii series was reviewed in the 1951-52 Yearbook and slightly re-arranged.
R. cerasinum
was moved into a subseries of its own along with
R. bonvolath
, a species which is not in general cultivation.
R. williamsianum
was also given a subseries to itself. In the Campylocarpum subseries
R. cyclium
was merged into
R. callimorphum
, and
R. croceum
into
R. wardii
. A large number of less well known spp. were either merged or given varietal standing only.
In 1954 Davidian, working alone, tackled the Campylogynum and Saluenense series. The former species is so variable that it now embraces all of the previously described species in the series, a few being given varietal names. The Saluenense series was reduced from 11 to 9 spp.
In 1956 Davidian and Dr. Cowan amended the Lacteum series to 14 spp. In 1963, after Dr. Cowan's death, Davidian reviewed the Triflorum series and brought some order into that badly "split" group. The subseries were reduced to four and the many spp. to 14 only, which is quite a relief!
R. caesium
was removed to the Trichocladum series which seems a more likely resting place.
This year, Davidian dealt with the Auriculatum, Edgeworthii, Scabrifolium, and Virgatum series.
R. griersonianum
now has a series to itself, and leaves
R. auriculatum
in a similar state.
The species
R. edgeworthii
now includes
R. bullatum
and
R. sciaphyllum
- there being no valid difference - and leaving only three in that series. In the Scabrifolium series
R. racemosum
is added, removing it from the Virgatum series. As this is almost or even quite indistinguishable from
R. hemitrichotum
which has always been in the Scabrifolium series it seems much more reasonably placed. He finds no valid differences between
R. oleifolium
and
R. virgatum
and both become
R. virgatum
, as the single species in the series.