Species In Our
This lovely species is in Subsection Pontica, along with many of our most familiar species (R. maximum, ponticum, catawbiense, brachycarpum, smirnowii, and yakushimanum). It seems most closely related to R. smirnowii. It was named after Baron F. von Ungern-Sternberg, 1800-1868, a professor at Dorpat University
R. ungernii is found in Northeast Turkey in the Caucasus Mountains at 2500-7000 feet. It generally grows on the north side of steep, moist, shady slopes along with beech, spruce, and fir. R. ungernii is often found with R. ponticum and R. smirnowii though the range of ungernii is broader than that of R. smirnowii and extends into Russia. Natural hybrids of ungernii and R. smirnowii are often found.
R. ungernii was first found by G. N. Kazbek in 1874 near Artvina, a city near the Black Sea in Turkey. Twelve years later it was described by E. R. Trautvetter. In 1886 it was brought to the St. Petersburg Botanical Garden and from there both R. ungernii and R. smirnowii were introduced into western Europe and then North America.
The growth habit of R. ungernii is open and upright, 8-20 feet high. The leaves, oblong-oblanceolate, are retained for 2-3 years. They are not as shiny as those of R. smirnowii but longer, 8-10 inches. The dense indumentum is a wooly, fawn grey. The inflorescence has up to 12-25 funnel-bell shaped white or pale pink flowers with pale green spots; it forms a lax truss. R. ungernii blooms later and lasts longer than many other rhododendrons. The ovary is densely glandular. Records show that it takes R. ungernii 10-20 years before it produces flowers (whereas R. smirnowii blooms in 6 years).
Peter Cox says R. ungernii is not as hardy as R. smirnowii, but that it will survive at the Arnold Arboretum. Greer lists it as hardy to -10°F. The Royal Horticultural Society Rhododendron Handbook of 1980 records an expedition of Apold, Cox, and Hutchinson to North East Turkey in 1962 which brought back several seed lots of R. smirnowii and R. ungernii as well as hybrids of the two. Lansing Bulgin, in his useful Rhododendron Hybrids: A Compendium by Parent, lists only two hybrids with R. ungernii as a parent: 'Summer Snow' [(ungernii x auriculatum) x maximum] and 'Maletta' [R. ungernii hybrid x ( auriculatum x discolor)]
I have never grown R. ungernii nor seen it bloom, but several members of the Species Study Group are growing it from seed.
Since it has beautiful flowers and blooms later and longer than many other rhododendrons, it should of great interest to hybridizers.
Elizabeth Carlhian, Concord, MA