Flora Wonder Blog: A May Day at the RSBG

Reuben Hatch

I'm a regular visitor to the Rhododendron Species Botanic Garden in Washington state, a world-treasure plant collection that contains far more than Rhododendron (“Rose tree”) bushes. It's quite a commitment as the journey is a four-hour drive to get there, and sometimes a five-hour drive back due to heavy PM traffic. Frequently I'm accompanied by long-time friend, Plantsman Reuben Hatch, but we don't stay long in the garden because he tuckers out quickly due to 84 years of age. But the drive is enjoyable – or interesting anyway – because we continue to learn from each other while we attempt to solve the world's problems. We're geeks for plants and we've travelled to most states west of the Mississippi, to Mexico, China and the Himalaya a couple of times. And when you think about it, the RSBG is a microcosm of all of those places; and so, as a Flora Wonder Blog reader, you have a passport and invitation to join us old white-haired geezers on our floral adventure.

Rhododendron glanduliferum

Upon arrival we quickly march past the admission window by announcing that we're Garden Members, and the various Ladies of the Till let us pass without question. The first stop is the sales yard, filled with Rhododendron species and hybrids plus a multitude of companion plants. I mentally catalog what I will purchase when I exit, and this time I couldn't pass on two Rhododendrons: R. glanduliferum and R. polytrichum. The R. glanduliferum is a species native to northeastern Yunnan, China, and besides its pinkish-white flowers I bought it for the new oblong-lanceolate leaves which were deliciously red-brown at the end of May. This species has been in cultivation since 1995, and was first described nearly 100 years before by botanist Franchett. The technical specific name is due to the pedicles (flower stalks), corolla and calyx being covered in stalked glands. The late Peter Wharton, curator of the Asian garden at the University of British Columbia Botanic Garden, discovered some specimens in China which grew to over 20 m tall. I definitely don't have room for such a thug in my garden without editing something else, but I was so taken with the color of the new leaves that I'll deal with that problem later.

Rhododendron polytrichum

I guess I was in a lush reddish-brown mood last week because I also fell for a Rhododendron polytrichum which also featured glandular young shoots. It was as if the culprit operators of the Species Garden knew I would be visiting with my cash, so they hauled these wonderful species from their growing houses up to the sales yard. Thankfully this polytrichum species (from China) won't get as large as the glanduliferum species. Nevertheless, Jens Nielsen, who has seen it in the wild, called it “a great beast of a plant.” So now both of these new species are in pots under the shaded overhang in front of my office, and already a number of visitors have expressed admiration, assuming that old Buchholz is a wizard at sourcing beautiful exotic plants. Well, join the Species Botanic Garden yourself – wherever you are in the world – and you can become a Rhododendron snob like me.

Rhododendron davidsonianum

I was tempted to make another purchase, but didn't, of R. davidsonianum, and the label described it well. It is a Chinese (Sichuan) species known as the “Concave-leaf rhododendron” which is native to forests between 1,500-2,800 m (4,900-9200 ft). Damn – I really should have bought it – and so would agree the Royal Horticultural Society since they praised it with the Award of Garden Merit. One would initially presume that the species was named in honor of Pere Armand David (1826-1900), the French priest, botanist and zoologist (he introduced the Panda bear to Europe)...but not so. The Rhododendron was actually named for Dr. W. Henry Davidson who was in China as a missionary doctor – in the right place at the right time – who administered treatment* to the injured plant explorer E.H. “Chinese” Wilson in 1910.

Lilium regale

E.H. Wilson

*At this point I should elaborate on Wilson's injury which occurred because he discovered (in 1903) the “Regal lily,” Lilium regale, in western Sichuan along the Min River. In 1910 he returned to the Min Valley to collect bulbs, but his leg was crushed during an avalanche of boulders. Wilson's leg was set with the tripod of his camera and he was carried back (to Davidson) on a three-day forced march. Thereafter Wilson referred to his “lily limp,” but it was this shipment of bulbs that established L. regale into cultivation. My plants of L. regale are not yet in flower – that occurs when it is 95 degrees F in July – so I'll talk about it again at that time.

Speirantha convalarioides

Also in the RSBG sales yard was Speirantha convallarioides, surprisingly, since it is a genus of only one-known species from southeast China. Commonly known as the “False Lily of the Valley,”* the evergreen's one-foot leaves can accumulate on a three-foot diameter clump. The flowers are strikingly white and sweetly fragrant...and I should have bought one of those also.

*The specific name of “convallarioides” is due to the resemblance to Convallaria, the Lily of the Valley, an herbaceous perennial in the Asparagaceae family which is hardy to USDA zone 3, or minus 40 degrees F. The genus name comes from the Latin word meaning “valley,” but be careful because all parts of this plant are very poisonous, containing cardiac glycoside.

Sorbus sargentiana

Charles Sprague Sargent

Reuben and I visited the RSBG about a month ago, but the new growth on Sorbus sargentiana was not present then. I hurried to it on last week's visit because the new growth is a lush purple-brown...but I was too late and the young leaves had already turned to green. What a short window then, and I wonder if some garden employees or volunteers have ever seen the color that I like so much. The fruits didn't impress me last fall with their orange color, but maybe they were still developing. In the Hillier Manual of Trees and Shrubs I read that the fruits are small, but scarlet, and that they are late in ripening. Hillier also promises “Rich red autumn colour,” but I've never seen it in autumn glory. The “rowan” was discovered by E.H. Wilson in 1903 and introduced by him in 1908 when he was employed by the Arnold Arboretum of Boston. The specific name honors Charles Sprague Sargent (1841-1927), the first director of the Arnold. Maybe a few berries will find their way into my pocket if I visit the tree this winter.

Viburnum sargentii

I was in time, however, to see Sargent's Viburnum in bloom. It says that V. sargentii is in the Caprifoliaceae family, but Hillier places it in Adoxaceae. I've steered clear of Viburnum production in my career even though I have a few in the Flora Wonder Arboretum, and my reason is that the genus is a root weevil magnet, plus it is susceptible to Sudden Oak Death, and who needs either of those two problems? Maybe you've heard of the old adage: “Viburnum when you can mulch 'em?”

Persea thunbergii

A plant I was hoping to see, Persea thunbergii, features red-brown new growth somewhat like the Sorbus sargentiana. I couldn't find the tree though, so maybe it too had already turned green, and I admit that the photo above was from a previous trip. The Persea is in the Lauraceae family, and with the specific name of thunbergii you know it is native to Japan, and was first described by Siebold and Zuccarini. It is listed as hardy to USDA zone 7, unlike Persea americana – the avocado – which is from Mexico and is hardy to only zone 10. The Persea name (Greek) is due to a related species, a sacred fruit-bearing tree of Egypt and Persia. A synonym for Persea thunbergii is Machilus thunbergii, and that generic name is thought to be from a Moluccan* name, or possibly the name of an insect (Machilis).

*Moluccas or the Maluku Islands are an archipelago in eastern Indonesia.

Clintonia andrewsiana

DeWitt Clinton

Clintonia andrewsiana was a fun discovery – I had never seen it before; that's embarrassing because it is native to Oregon and northern California, growing in shady areas of the Sequoia sempervirens forests where I have been plenty of times. I hope to find the rhizomatous perennial again in autumn to see its bright blue berries (about 1 cm long). The genus is distributed across North America and eastern Asia, and was first described in 1818 and named after DeWitt Clinton, an 18^th century botanist and politician.* He was a US Senator, Mayor of New York City and the 6^th Governor of New York.

*Oddly, Clinton managed his personal financial affairs poorly, but nevertheless he appeared on the 1880 United States bank note for $1,000.00

Dryopteris polylepis

The Species Garden is famous for its ferns, and they absolutely thrive in the woodland setting. On every visit I discover a new species that has eluded me before; that is, if I can trust the labels. Dryopteris polylepis is from Japan, I read, and I wish my wife could be with me and perhaps tell me more. When I think of her, if she was a plant she would probably be a fern. Anyway the specific name polylepis means “many scales,” and I know that thanks to Sue Olsen's Encyclopedia of Garden Ferns (Timber Press 2007). I like her concise description: “Grow this fern for the excitement the scaly new foliage brings to the springtime garden and the assured ornamental contribution of the foliar black and green highlights throughout the rest of the year. It is an undemanding citizen of the woodland garden with a preference for light shade.” Earlier I learned that the name Dryopteris is from the Greek drys for “oak or forest” and pteris for “fern.”

Dryopteris lepidopoda

Another attractive Dryopteris is the species lepidopoda from the Himalaya, China and Taiwan, with the specific name meaning “scaly feet.” Sue describes the emerging fronds as possessing “warm sunset tones” and adds, “Additional colorful new fronds are produced throughout the summer giving continued buoyancy to the display.” I could stay in the woodland garden all day admiring the ferns and reading Sue's poetry.

Lilium mackliniae

Frank Kingdon Ward

A sweetheart in the garden is Lilium mackliniae, commonly called the “Shirui lily” because the rare species is found only in the upper reaches of the Shirui ranges in northeastern India at 5,680-8,500 ft (1,730-2590 m). You know from the suffix of the specific name that it honors a woman, and indeed the flower was discovered by plant explorer Frank Kingdon Ward who named it for his wife Jean Macklin. I was pleased to acquire the lily last year at the RSBG's plant sales yard. I have not looked myself, but I have read that if you look through a microscope you can observe seven colors, but to my eye I just see bluish-pink petals. Locally the flower is called Kashong Timrawon and it represents kindness, prosperity and a happy life.

Primula flaccida...or ?

The charm of Lilium mackliniae is that its bell-shaped flowers bow in modesty. More dramatic was a Primula with the label reading flaccida for the specific name. There was nothing “flaccid” about it however, so I don't know its true identity. Maybe the label was for a species that no longer grows near that spot, or was not yet in flower.

Primula pulverulenta 'Bartley Strain'

Another primula was in flower, P. pulverulenta 'Bartley Strain', and the species is native to damp habitats in China. The specific name means “dust” (as in pulverized into fine powder) and refers to the white layer (farina) covering the stems. Normally these candelabra flowers are colored from deep red to mauve, but I liked the pale pink of the 'Bartley's Strain', and it demonstrates that subtly-colored flowers have a place in a sophisticated garden.

Kalmia 'Little Linda'

Peter Kalm

The outer petals of Kalmia 'Little Linda' were fiery-red but the blossoms were not fully open, so maybe she dulls somewhat when they are. I don't recall seeing other Kalmia in the garden, which is strange for a rhododendron garden like the RSBG. Since the label didn't mention a species I presume that 'Little Linda' is a hybrid. I have read that Kalmia is a genus of about ten species, native to North American and Cuba. On britannica.com, it says there are “about seven species which occur in North America and the West Indies.” I don't know anything about Cuban or the West Indies Kalmia, but there are two species native to the Pacific Northwest, K. occidentalis and K. polifolia var. microphylla which are low shrubs commonly called “Bog laurels.” The genus name was bestowed by Linnaeus and honors Pehr Kalm, a Finnish disciple of Linnaeus. Kalm (1716-1779) was an explorer and botanist who was commissioned by the Royal Swedish Academy to travel in North America to bring back seeds and plants that might be useful for agriculture. He covered a lot of territory, and is credited with the first description of Niagara Falls written by a trained scientist.

Huodendron tibeticum

Alfred Rehder

Huodendron tibeticum is in the Styracaceae family and it was first described by Alfred Rehder,* the German-American botanist who worked at the Arnold Arboretum of Harvard University. It is native to China, Tibet and Vietnam, and though hardy to only USDA zone 8 (10 degrees F) the garden's recently planted bush will probably survive, judging from other tender RSBG plants that would likely die for me. It has been called a “False Styrax,” with its small white hanging flowers, but there were no blossoms evident at my visit, while our plants of Styrax japonicus are blooming at this time. The word huo means “fire” in Chinese, so huodendron is “fire tree,” and that is due to the leaves' brown-red new growth – the color I like so much.

*Rehder is honored with the genus Rehderodendron which is also a Chinese tree in the Styracaceae family.

Acer palmatum 'Emerald Lace'

Acer circinatum 'Burgundy Jewel'

Maples fit in well at the RSBG, and the Japanese maples especially so as understory trees under the Douglas fir canopy. A healthy specimen of Acer palmatum 'Emerald Lace' is spreading lustfully, and they probably planted it too close to the path just as I have done at the nursery. Wisely an Acer circinatum 'Burgundy Jewel' was placed in full sun which is necessary for the purple-red foliage to develop. I was happy to donate it to the garden because 1)it's a great selection and 2) because it was discovered in Washington state by Gordy Halgren of Peacedale Nursery. The original seedling of 'Burgundy Jewel', however, was supplied to Peacedale by an Oregon nursery, namely Drake's Crossing.

Acer shirasawanum 'Aureum'

I have long admired a large specimen of Acer shirasawanum 'Aureum'. I have grown the cultivar longer than the Species Garden but I don't have any nearly as large because I always sell mine. On this visit I didn't focus on the canopy, but rather I was attracted to the trunk, and the light on it was perfect. I can't imagine any sculpture more beautiful.

The RSBG is a wonderful resource for plants, and today's blog only highlights a few things that I saw. We stayed in the garden for less than two hours, but the following photos reveal that there was much more to be seen. I encourage all readers to visit the garden, and if you do you will probably end up as a member like I did.