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Species In Our Midst
Rhododendron micranthum
by Betty Carlhian
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Rhododendron micranthum s. Micranthum s.s. Micrantha
A monotypic and distinct subsection, whose closest ally is probably subsection Lapponica but from which it differs in its winged seeds which suggest a relationship with Maddenia or Boothia
Epithet
"Small flowered" from the Greek. In Chinese it is known as "shining mountain white" or "white mirror."
History
R. micranthum was first described by Turczaninov in 1837 from a specimen collected on the mountains north of Peking. Wilson introduced R. micranthum1901 from Hupeh. It was illustrated in the Botanical Magazine in1908.
Distribution
R. micranthum is widely distributed; it grows wild from North Korea through central and northern China and Manchuria in thickets and scrub on cliffs and dry gorges and on ridges, at elevations from 1500-2500 m (5000-8000 ft).
Hardiness
Reports on the hardiness vary. Greer says -5°F in his book, Guidebook to Available Rhododendrons, 3rd edition, but David Leach lists -25°F-H1. People in the Concord, MA area say it is quite hardy.
Description
R. micranthum forms a bushy evergreen shrub, 4 to 5 feet tall, looking more like a Spirea or Ledum (now rhododendron) in growth habit. The leaves are oblong-elliptic, less than 1" long and very narrow. They are glabrous above and densely scaly and light brown below. The branches are slender and graceful. The flowers are white, unspotted, and tiny. The corolla is funnel campanulate and about 1" across. The inflorescence may contain as many as 50 flowers. The rachis is long unlike most other lepidotes. Although the flower buds become quite large by late autumn, the plant does not flower until after most rhododendrons in June or July.
Hybrids
I can find no record of any success in hybridizing R. micranthum.
Comments
For a plant with so many positive qualities, i.e., hardiness, good form, number of flowers, late time of bloom, it is surprising that this species is so little seen in our collections. Because there is quite a good deal of variation between the cultivars of R. micranthum it would seem to be a plant ready to be worked with to make superior forms available for our gardens.