Species In Our
R. tsariense is considered to be in Subsection Campanulata by the traditional taxonomists, but put in Subsection Lanata by David Chamberlain in his revision of the genus. In other words, this interesting little plant presents problems to those who are determined to make sense of the relationships of the species rhododendrons. But from a horticulturist’s point of view, tsariense is an unambiguous gem!
R. tsariense (along with R. lanatum, lanatoides and circinnatum, in Chamberlain’s ordering of this subsection) is distinguished by its thick, rather leathery leaves with an underside of dense, wooly indumentum. Its little leaves are obovate (wider towards the tip) to oblong, shiny dark green above, up to 2 1/2 inches in length, with deeply impressed veins. Underneath is the little plant’s real glory: thick, cinnamon indumentum. In Chamberlain’s exact botanical language, "…the lower surface [has a] dense rufous-tomentose indumentum composed of ramiform hairs". The leaf petioles are also thickly covered with this red-brown wool, as is the midvein on the upper surface of the leaf. New growth is cinnamon-colored with tomentum as well.
R. tsariense produces a small truss of 2-5 flowers, nicely proportioned for a small plant with small leaves. The rachis (central stalk supporting the flowers) and the pedicels (flower stems) are densely covered in cinnamon wool. The flowers themselves are campanulate (bell-shaped) up to 1 1/2" long, cream or white, often with a pink flush and occasionally flecked with red. All the reproductive parts are very wooly at their bases, as is the seed capsule. Even its branchlets are densely wooly.
R. tsariense is a compact plant, rarely reaching 6’ in height in cultivation. It is stiff and twiggy, but not especially dense. Harold Greer gives it a rating of 3/5/3 for its flowers, plant & foliage, and performance; I agree with his ‘plant and foliage’ rating, but think he is a bit harsh in his flower rating. The specific name is geographical, from Tsari in Tibet. Greer rates its hardiness as -5ºF. My young plant has survived -8ºF so far, but has not had its buds tested below 0ºF yet.
According to H. H. Davidian it was first found in 1915 by R.E. Cooper at Pumthang in Bhutan, then by Ludlow and Sherriff in several localities in south Xizang, by Taylor in southeast Xizang, and finally by Kingdon-Ward in Assam in 1938. Chamberlain locates it in China, NE India and possibly Bhutan. It grows in the wild on cliff edges and among rocks and open hillsides, in bamboo forests, in fir forests, all at moderately high elevations between 10,000 and 14,500’; it is fairly common locally where it is found. It was introduced by Ludlow and Sherriff with plants from Bhutan. According to Davidian two forms are in cultivation, a small, rounded compact plant up to 2’ and a broadly upright shrub 4-5’ high. Davidian and Cox agree that the plant is slow growing and slow to reach flowering size. Cox cautions that the plant is bud-tender once the buds have started to swell, but since it is an early midseason bloomer, that should not be too much of a problem around here.
Chamberlain reports that tsariense hybridizes in the wild with its close relative, R. lanatum. Lansing Bulgin, in his useful if now outdated book, Rhododendron Hybrids: A Compendium by Parent, 1986, lists only two hybrids with tsariense: x ‘Sangreal’ to produce ‘Snugbug’ and x yakushimanum to produce ‘King Bee’.
I have had a plant of the species for only seven years now and it was badly slowed down by extensive vole tunneling; the rodents did not eat its roots, just heaved it up and dried it out. Even so it has already produced a few blooms, so my experience does not agree with the observations of the experts about slow bloom habits. Maybe my plant was scared into reproducing early, as sometimes happens, by its near-death from the vole tunnels. I also have a gorgeous unnamed tsariense-yak cross which looks like a more robust form of the species and blooms nicely every year with larger flowers than the species. Both the species and the cross are among my most favorite plants and one of the most decorative in the garden. Right now, with a shiny crust of snow around them, they and my bureavii species and crosses are stunning with their dark leaves and luscious cinnamon indumentum glowing in the cold sunlight. Year-round beauty indeed!
Susan Clark, Concord, MA