Species In Our Midst
Rhododendron fastigiatum

Rhododendron fastigiatum
Picture by S & J Perkins

Rhododendron fastigiatum is a hardy lepidote in the subsection Lapponica. Its species name means "erect" but all the good forms are not. Its Chinese name translates to "densely branched rhododendron" which seems to be a better description. Introduced to the west by Forrest in 1906 from western Yunnan and reintroduced several times since, it can be found growing in its native habitat of thickets on rocky hills in west and northwest Yunnan and southwest Sichuan at 10,500-16,000 feet. Peter Cox remarked on entire hillsides, in its native Yunnan, covered with R. fastigiatum in bloom associated with creamy white R. cephalanthum and pale yellow R. trichocladum. It also often grows near R. yungningense (formerly R. glomeratum).

Greer rates it among the finest of all the scaly leafed rhododendrons for its hardiness and usefulness especially in the small alpine forms. The species can be variable in growth habit from 6 inches to 4 feet. The small elliptic or oblong leaves about 8 mm x 4 mm are in terminal clusters on the branchlets. The leaf's upper surface is glaucous-grey or pale glaucous green especially on the young growth and many selected forms have excellent glaucous foliage. The dense scales on the under surface of the leaf almost touch and are, according to Davidian, pale to dark brown in color. Flowers are in terminal inflorescences of 2-5 flowers. The long stamens and stigma extend beyond the corolla which is usually purplish blue but can be lavender-rose, deep purple-blue, deep lavender, deep blue or even rarely pinkish. Closely related to R. impeditum, Cox admitted "that 2 of his introductions from Cangshan are impeditum not fastigiatum as first thought" and that some "forms of impeditum are actually fastigiatum".

Two Gable crosses of R. fastigiatum with R. minus Carolinianum Group, 'Purple Gem' (-20°F(-29°C) ) and 'Ramapo' (-25°F(-32°C)) are probably the most commercially important hybrids. 'Purple Imp' has similar heritage. 'Blue Diamond' (`Intrifast' x augustinii) has been used extensively in hybridizing for blue lepidote color. Unfortunately 'Blue Diamond' is not rated very hardy mostly because of R. augustinii parentage and therefore its many hybrids have similar hardiness problems. See the Blue Lepidote Project

Other hybrids with at least 1/4 R. fastigiatum are:

'Ramolet' (open pollinated 'Ramapo')
'Blue Diamond' ('Intrifast' x augustinii) -5°F (-20°C)
'Oudijk's Favorite' ('Intrifast' x augustinii) -10°F (-23°C)
'Blue Mountain' (R. fastigiatum FCC x 'Blue Tit')
'Augfast' (R. augustinii x fastigiatum) 0° F(-17°C)
'Intrifast' (R. intricatum x fastigiatum) -15°F (-26°C)
'Fasthip' (R. fastigiatum x hippophaeoides)
'Delp's Carefree' (R. minus var. minus, Delp's tetraploid form x fastigiatum) Zone5(4)
'Tear Drop' (R. minus var. minus, Delp's tetraploid form x fastigiatum) Zone5(4)

References

Cox, P.A. The Smaller Rhododendrons,1985
Davidian, H.H. The Rhododendron Species Vol I Lepidotes 1982
Dawes Arboretum Special Report on Rhododendrons
Greer, H.E.Greer's Guidebook to Available Rhododendrons. 3rd ed.1996
Rhododendrons of China, 1980 ARS and RSF
Salley, H. and H.E. Greer Rhododendron Hybrids 2nd ed. 1992