The Maximum Effect
David G. Leach, Brookville, Pa.
My sorrowful disenchantment with the Rosebay rhododendron, R. maximum, as a parent for hybridizing was publicly recorded in a threnody published in the April 15, 1965 issue of The Quarterly Bulletin. I offered as supporting evidence the conspicuous scarcity of notable hybrids in the past in which this species has figured as a parent, and presented a table showing the poor to indifferent results from 69 of my own first and second generation maximum crosses. Well over a thousand hybrid seedlings had yielded nothing of quality or distinction. Since that time two outstanding new hybrids deserve recognition as exceptions to the generally disappointing record.
The first resulted from a cross of maximum x strigillosum, made by Edmond Amateis, with pollen of H. L. Larson's fine form of the Asian species. It produced a dazzling scarlet, without trace of blue, which blooms in early May. The globular truss, about 6"x6", is full and firm, the numerous florets an inheritance from the seed parent. The black basal nectaries and the deeply impressed leaf veins were contributed by strigillosum, which did not, however, pass on its hairy, bristly character. The flowers of its offspring are displayed with unusual poise and elegance atop a contrasting ruff of exceptionally attractive, bright green foliage. Mr. Amateis has named this clone 'Harold Amateis', for his brother, and it is now being propagated for commercial introduction. This luminously beautiful new scarlet hybrid has been completely bud hardy so far in U. S. D. A. plant hardiness zone 6a.
The other new hybrid came from a cross I made on R. maximum, in 1958 with pollen of ungernii x auriculatum F2, sent to me by Joe Gable. It bloomed for the first time in 1968, on June 21st, with eleven white florets nearly four inches across in an immense somewhat loose, dome-shaped truss about nine inches in diameter. The six-lobed flowers are enlivened by a greenish-yellow dorsal blotch. Branches which had set buds did not send out new growths until after the blossoms had faded, so apparently the floral display will not be obscured as it is on so many late blooming hybrids. This clone has been named 'Summer Snow'.
I have been trying for some years to create an array of very late blooming hybrids, which are badly needed in the East, but the dismal failure of maximum to yield quality progeny brought only disappointments until this year. When the breakthrough came, it was dramatic. We are not accustomed to seeing, in zone 5a where the routine winter low is -20°, either flowers or trusses of such sumptuous size as those on 'Summer Snow'. The glistening white flowers of heavy substance are almost theatrical, imparting an opulent charisma which is unique for this climate. It is easily the largest flowered hybrid ever to bloom at Brookville.
After nine years the plant is about four and a half feet tall and equally broad, with large leaves. It has survived -35°, but I am tentatively estimating its bud hardiness as H -12° to H -15°.
Having damned the Rosebay rhododendron as a sire, it is only fair to report that it has now produced two distinguished children.