JARS v37n2 - R. griersonianum And Some Of Its Hybrids

R. griersonianum And Some Of Its Hybrids
Arthur W. Headlam, Bentleigh, Australia

Griersoniana subsection, R. griersonianum , was discovered by George Forrest in West Yunnan and Burma-Yunnan frontier at 7,000 to 9,000 feet, and was named after R.C. Grierson, of the Chinese Maritime Customs at Tangyueh.
It was awarded the F.C.C. in 1924 (T.H. Lowinsky and L. de Rothschild of Exbury). Often a straggling shrub up to 10 feet, with young shoots clothed in floccose hairs and setose glands, carrying long tapered flower buds, the outer scales having long tapering tips. The leaves up to 8" long by 2" broad, lanceolate, dull mat green above with loose whitish to buff woolly indumentum below.
Flowers are produced in trusses of 5 to 12, up to 3½" long by 4½" wide, funnel campanulate, 5 lobed bright geranium scarlet, quite different to any other species in the Yunnan and North Burma region.

Rather cold tender when young, but there is no problem in this regard in Australia. R. griersonianum has been much used by hybridizers, some of the best known being 'Elizabeth', 'Tally Ho', 'Vanessa', 'Matador' and 'Fire Glow'. One of the most striking of the R. griersonianum hybrids is 'May Day', ( R. griersonianum x R. haematodes ). Up to the 1969 Rhododendron Handbook there were 155 crosses flowered and registered in England alone! One wonders what monumental figures will be disclosed when the next Rhododendron Hybrid Handbook is eventually published.

R. haematodes is described as a small shrub, as much as 10 feet high with young stalks woolly tomentose. Leaves up to 3" long by 1½" broad, oblong to ovate, dark green above, densely rufous woolly tomentose below. Flowers in a truss 6/12, up to 2" long, tubular campanulate with fleshy glistening flowers, generally deep crimson to scarlet. Hardy and late flowering, and usually takes some years to become free flowering.

Located in a prominent position near the pond in the National Rhododendron Garden at Olinda is a very striking seedling of 'May Day'. It was introduced and registered 'Glen Glow' by Alan Raper, a nurseryman and past President of the Australian Rhododendron Society.

The most outstanding features of 'Glen Glow' are its glowing color of bright red (Geranium Lake, H.C.C. 20), its ability to produce a profusion of flowers at an early age, carrying 16 flowers, with a red calyx, to the truss, yet against these good features it has the problem of degeneration as the plant ages, the flowers become smaller, it loses intensity of color and the general vigor of the plant is impaired. However, these faults may be overcome by grafting onto a compatible understock, in this instance R. arboreum seedlings have proven to be satisfactory. However, this method naturally adds to the cost, and it is a pity that such a fine plant is lost to the general trade.
A connoisseur would, knowing the circumstances, be quite prepared to pay an extra premium for such an outstanding plant.