Favorite Rhododendron Species in the Flora Wonder Arboretum

Rhododendron barbatum

Rhododendron macabeanum

Rhododendron montroseanum

 


I've mentioned before that I used to work for a large wholesale nursery, and there we grew thousands of Rhododendrons*, hardy hybrids mainly. I planted, pruned, fertilized, watered and harvested scads of plants, so to some degree I would have been considered an expert on Rhododendrons. But I never thought so, nor did I consider the nursery owner an expert either. We could crank out crop after crop of varieties that East Coast brokers told us to grow. I learned that 'Bow Bells' had a pretty blossom but was a naturally leggy plant, that 'Jean Marie de Montague' was brittle when you tied up the top to dig, and that 'Vulcan' would burn in full sun whenever the temperature soared into the hundreds. But I knew nothing about the origin of these hybrids, about who preformed the crosses and from what species.

*From Greek rhodon for “rose” and dendron for “tree.”

Rhododendron arboreum ssp. arboreum

All of this occurred in the early 1970's, and back then I dismissed the Rhododendron genus as a fairly boring group of shrubs. They were evergreen blobs that filled the landscape, and were redeemed for only a couple of weeks in spring and summer when they bloomed. Otherwise they were forgettable. All of that changed in 1979 when I temporarily quit the nursery business to explore in the Himalaya, and I remember walking under them – R. arboreum, the national flower of Nepal – and walking among the alpine scrubs at the higher elevations.

Reuben Hatch

Now I have a nice collection of Rhododendron species due to my membership in Washington state's Rhododendron Species Botanical Garden. Furthermore I befriended Reuben Hatch (my Grandfather) about thirty years ago, and he was a nurseryman who specialized in “Rhododendrons for the Discerning Gardener,” so I have dozens of starts from his collection. Now I appreciate the genus for the foliage as much as for any blossom. Even though I don't travel as much as I used to, one of the greatest delights is to witness trees in the wild in far-off places and then to also grow them yourself...thence the Flora Wonder Arboretum. Let's take a stroll through the grounds and I'll point out some of my favorites.

Abies forest in the Himalaya

Rhododendron kesangiae

R. kesangiae is a lofty tree-like species with large glossy-green leaves. Flowers can vary from purple, pink, to pure white and I have the var. album form. It is endemic to Bhutan and was named in honor of Kesang, the Queen Mother of Bhutan, and the suffix iae denotes a female as name recipient in botanical nomenclature. Even though it grows up to 10,000' in altitude in the eastern Himalayan foothills, its hardiness rating is only to 5 degrees F (-15 C), nevertheless my young plant survived to 3 degrees F last winter with no apparent damage. I first saw R. kesangiae as an understory tree in the fir forests about 25 years ago, but at the time I couldn't identify the species, and surprisingly – even though common – it was first described in only 1989 by D.G. Long and K. Rushforth.

Rhododendron strigillosum

Rhododendron strigillosum

E.H. Wilson

Dr. Frank Mossman

Rhododendron 'Taurus

R. strigillosum is a Chinese species with a slow rate of growth, or at least my one plant has been restrained. It is an attractive foliage plant – as long as you keep weevils off of it – due to long narrow leaves. Surrounding the flower buds the leaf petioles display noticeable reddish hairs, and it is known in China as mang ci dujuan, or “prickly Rhododendron.” The definition of strigillosum is that which has a strigil, an instrument with a curved blade, used by ancient Greeks and Romans for scraping the skin at the bath. Anyway R. strigillosum features blood-red flowers that bloom as early as March, so you'll see it planted in some of the world's top winter gardens. It was introduced into England by the famous plant explorer E.H. Wilson in 1904 when he was collecting for the Veitch Nursery firm. My start came from Reuben Hatch who has a nice form of the species, as variations in the wild occur and some plants bloom with a washed-out red blossom. R. strigillosum is a parent of some notable hybrids, my favorite being 'Taurus', bred with 'Jean Marie de Montague' by the late plantsman Frank Mossman of Vancouver, Washington.

Rhododendron orbiculare 'Edinburgh'

Rhododendron orbiculare 'Edinburgh'

Rhododendron orbiculare 'Exbury'

No mention of my favorites can avoid R. orbiculare, and I have two from highly esteemed collections: one, from the Royal Botanic Garden, Edinburgh in Scotland, and the other the Exbury form from the famous garden in Hampshire, England which belongs to a branch of the Rothschild family. Believe me, there is absolutely nothing wrong with filthy wealth as long as it is spent on featuring our planet's floral best. R. orbiculare is so-named for its round leaves and it is a dense shrub that will grow to about three feet in ten years. The campanulate (bell-shaped) flowers are deep pink and appear in May, and at that time the Chinese species is everybody's favorite rhododendron. Even when not in bloom the green rounded leaves with a heart-shaped base have insured its popularity since its introduction in 1904, but it took until 2002 before the Royal Horticultural Society deemed it worthy of an Award of Garden Merit. I beat the RHS by at least 20 years when it gained the plebian Buchholz Award of Excellence in 1980 and it is currently being propagated and sold by our nursery.

Rhododendron campanulatum ssp. aeruginosum

Rhododendron campanulatum ssp. aeruginosum

Another bell-shaped bloomer is R. campanulatum ssp. aeruginosum, except that I wouldn't give a hoot if it never bloomed at all. [I had to re-read the preceding sentence carefully so that I didn't repeat what an enthused customer declared a few years ago at the nursery when he witnessed an R. camp. ssp. aer. in spring – “that's the most incredible thing I never saw.”]. What is so incredible are the new blue leaves, for they perk up at attention like the fabulous Hosta 'Blue Mouse Ears'. I have seen this rhododendron in the wild, or at least I think I have – remembering the blue metallic sheen – in the alpine regions of Nepal at about 13,000' elevation. I don't know, though, because every Himalayan plant in situ appears different than it does in a sea-level garden, and also because the explorer himself is giddy with much excitement about what he is observing. The ssp. aeruginosum name is a Latin word meaning “copper rust” due to the blue-green pigment.

Rhododendron augustinii 'Smoke'

Rhododendron augustinii 'Smoke'

Augustine Henry

Do you see that empty space in the garden? – it used to be home to R. augustinii 'Smoke' but I gave up on it for looking horrible after last year's cold winter. It survived and looked good after a couple of previous winters that dropped to even a few degrees more cold, but that can be the way with plants: they don't always reveal to you what they are going through. I've left the space open with the intention of refilling it with 'Smoke', or another cultivar of R. augustinii, but never found it available last year. Oh well, you don't always get a second chance with plants, and just be thankful that you had a few good years of a relationship. It was an example where the flowers impressed me and the foliage really never did; blooms could range in color form whitish blue to deep blue to a purplish blue, but I don't know if the variation was on account of different collections, or from seeing the same clone at different times and in different soils. What struck me most was the luminosity of the flowers which seemed to glow even on cloudy days. The R. augustinii species is from Sichuan and Hubei in China and was named for Augustine Henry (1857-1930), the Irish custom's inspector who became a noted plant discoverer in his adopted country. Henry sent over 15,000 dried specimens and seed to Kew Gardens as well as 500 plant samples, and is well-known for assisting plant collector E.H. Wilson in his quest to collect seed of Davidia involucrata.

Rhododendron boothii

Joseph Hooker

One of the gems in the conservatory at the Rhododendron Species Botanical Garden is R. boothii and thanks to them I have a small plant of it. The small yellow flowers in spring are nice but certainly not awesome, and it is the copper-red new growth on hairy leaves that I admire the most. It is probably hardy to only 10 degrees F, USDA zone 8, so I also keep my plant in a heated greenhouse. Collecting plants from the temperate rain forests of the Eastern Himalaya is an invitation to the plant gods to cause your greenhouse heater to fail – you know, to keep you humble – and I have suffered many such losses in the past. R. boothii was described by Thomas Nuttall and published in Hookers Journal of Botany, 1853, and the type was located in Bhutan at 5,000' elevation as epiphytic on oaks. The specific name honors the botanist T.J. Booth (1829-?). S. Hootman of the RSBG reports that it is very slow-growing and requires excellent drainage. Furthermore the only place where he has seen it “growing in the wild is on the sides of maple trees, rooted into the bark.” It is fascinating to know that the Director of the Rhododendron Species Botanic Garden – in the 21^st century – along with his American cohorts (Far Reaches in Washington state) and the Coxes (from Glendoick in Scotland) are still discovering species and forms that Britain's Hooker and the other great plant explorers undertook one hundred and sixty-some years ago. Hopefully after Hootman et. al. grow long in the tooth there'll be replacements who will carry on in the spirit of plant exploration in our world's far-flung places.

Rhododendron bureavii

Rhododendron bureavii

Rhododendron bureavii

Louis Bureau

R. bureavii was one of my first acquisitions from plantsman Hatch. When my start was large enough I planted it out in the Display Garden in full sun where it scorched nearly to death the first summer. I dug it up and gave it two years to recover in a shaded greenhouse, then replanted it outside in a more shady location – or in a shadow as the Dutch say. Flowers are white to pink with purple spots inside; they are mildly attractive to me but it's surprising that R. bureavii received an Award of Merit for the flowers in 1939. The Award of Merit for the foliage took until 1972, but the foliage is the reason I grow it. Leaf undersides display a luxurious dose of reddish indumentum and as you can see the new growth is equally impressive. It is a compact shrub growing more broad than tall, and it comes from Sichuan and Yunnan Provinces in China at 9,186-14,763' (2800-4500m). It was introduced by E.H. Wilson and described by the botanist Adrien Franchet.* The specific name honors Louis Edouard Bureau (1830-1918), a French botanist and professor of taxonomic botany in Paris.

Adrien Franchet

*There are a lot of botanic names and descriptions given by Franchet (1834-1900). He was based at the Paris Museum of Natural History where he described the flora of China and Japan based on collections made by French Catholic missionaries such as Armand David, Pierre Delavay, Paul Farges, Jean-Andre Soulie and others. The Flora Wonder Arboretum contains plant samples from all of these missionaries.

Rhododendron faithiae

Rhododendron faithiae

I first became enamoured with R. faithiae for its foliage, and not at all for its flower. New growth on many rhododendron species is actually more fantastic and colorful than the blossoms, and the Rhododendron Species Botanic Garden is an excellent place to study their mature specimens. Their description claims that it is a “very rare species (known from only two or three locations in the wild).” They claim that it exhibits large, fragrant white flowers in mid-summer, but my plant hasn't bloomed yet. RSBG Director Steve Hootman writes, “One of the most exciting finds that Peter Cox and I have ever had together.” Furthermore, Cox says that it is the hardiest scented species. R. faithiae (da yun jin du juan in Chinese) was first described by Woon Young Chun in 1934, but I'm not certain who the “Faith” woman is who is honored with the name. All I could come up with is Faith Fyles (1875-1961), a Canadian botanist and plant illustrator, but I don't know if she had any connection with Chinese Chun.

Rhododendron morii

Rhododendron morii

Rhododendron morii

R. Hatch is my source for R. morii and hopefully my specimen is true to name. It is a Taiwan native first described by Hayata in 1913, and in cultivation since 1918. It was introduced by E.H. Wilson in 1917 when he was working for the Arnold Arboretum, and despite coming from Taiwan it has proven absolutely hardy for me. The flower blooms pure white with red spots inside, but when it first develops it is positively pink. I'm sure there is some variation in the species – and maybe a lot – but that's what I mean when I wonder if my plant is correctly named. Ideally the Flora Wonder Blog should be a relationship where you contribute something, so I invite a rhododendron know-it-all to weigh in.

Rhododendron exasperatum

Rhododendron exasperatum

Rhododendron exasperatum

The specific name for R. exasperatum might lead you to assume that there was confusion about where to place it botanically, but in fact it was named by Harry Tagg in 1930 for its rough-ribbed leaves. Exasperate is from the Latin verb exasperare which is based on asper for “rough.” It is a unique species that I can usually identify in a garden even from a distance. My only gripe is that it is barely hardy in Oregon, so I dug my one plant after a brutal winter and now keep it indoors in a pot. Flowers are deep red and attractive, but I especially admire the purplish new growth, then later leaves become dark green on hairy stems.

Rhododendron forrestii var. repens

George Forrest

We decided to propagate and offer liners of R. forrestii var. repens. This variety is more low-growing than the normal forrestii species, and most of the time it is designated as the Repens Group due to some variation. The creeper's habit is terrestrial but it can find purchase on mossy rocks and it thrives with PM shade. The flowers are bell-shaped and deep red in color, and they are all the more spectacular because they are relatively large compared to the tiny green leaves. Forrest's rhododendron is native to northwest Yunnan, southeastern Tibet and also upper Burma (Myanmar) between 10,000-14,000' elevation. Forrest discovered the species in the summer of 1905 in Yunnan, but a few weeks later he barely escaped with his life from a band of murderous lamas bent on killing all Westerners. Running barefoot through the forests all of his material was lost except for one small piece which was sent earlier to Britain and described by botanist Diels. Forrest was back in the same area again in 1914 and 1918, but the undersides of the leaves were of a different color than the original type sample. Later Frank Kingdon Ward discovered clones that were named 'Scarlet Runner', 'Scarlet Pimpernel' and 'Carmelita'. We also grow a related species, R. chamaethomsoni, in our shaded former-basketball court.

Rhododendron makinoi

Rhododendron makinoi

Tomitaro Makino

I collected R. makinoi quite a few years ago and I was initially attracted by the long narrow leaves; and regular Flora Wonder Blog readers know that I am a fan of the skinny. I had it in the garden for at least ten years before I discovered that makinoi is a Japanese name and that it was indeed native to Japan (central Honshu). Flower color can range from pink to off-white, and thankfully I have a strong pink form from the Hatch garden. The specific name honors Tomitaro Makinoi (1862-1957), a Japanese botanist noted for his taxonomic work. He has been called the Father of Japanese Botany, and in addition he did overtime work in the bedroom and fathered 13 children. Makinoi named over 2,500 plants including 1,000 new species and 1,500 new varieties, and his birthday (April 21) is celebrated in Japan as Botany Day. I would love to visit the Makinoi Botanic Garden located in his hometown of Sakawa in Kochi Prefecture on Shikoku Island.

Frank Kingdon Ward

So that's less than 20% of the interesting rhododendron species in the Flora Wonder Arboretum. A lot of my factoids for this blog come thanks to the internet, and again I wouldn't consider myself an expert on the genus. I'll close with what the great plant explorer and writer, Frank Kingdon Ward, wrote: “The genus Rhododendron carries the universal hallmark of excellence.”