Three Plants of the Sanguineum Subseries From the 1950 Rock Expedition
It is now eight years since Rock sent back the collection of rhododendron seeds from China and the border of Tibet. From time to time in the Society Bulletins and Book there have appeared short notes on species that have bloomed for the first time. It is my belief that by far the greatest number of plants grown, and still growing today, from that expedition belong to the subseries sanguineum.
The plants that compose this subseries, as is so well known, are probably the most variable in the rhododendron family of species. The variation is not in foliage and habit, for many are quite alike here, but rather in the color of the corolla. R. didymum which was sent back under several numbers is stable in all respects, and there is no variance from the type. As to the others of the sanguineum numbers, hardly any two are alike. I doubt very much whether there was a mixing of seeds, but rather that the group is growing in a state of flux in the wild. Plants of identical foliage and habit under a number will have bloom that ranges from red to yellow.
Fig. 27. Sanguineum Subseries (R. 136)
Most of the Rock plants in the Sanguineum series are barely two feet tall, others hardly a foot, and appear very slow. R. sanguineum (R. 136) (Fig. 27) is perhaps ten inches tall and less than ten inches across, and seems in no hurry. Its first bloom this spring in late April was a pale clear yellow, unspotted, and nearly an inch wide. Its eglandular calyx, and yellow corolla will place the plant near R. himertum.
Fig. 28 Sanguineum Subseries (R. 150)
The second plant R. sanguineum (R. 150) (Fig. 28) has a dark red corolla, and is slightly larger than the above, perhaps nearly one and one quarter inches across. Plants under this number are extremely shy to bloom and meet most of the requirements of R. sanguineum itself. John Bacher who raised hundreds of species in the sanguineum series from the 1932 Rock expedition in the Swiss Floral Co. garden on Holgate Ave. had not seen any plants bloom even after fifteen years.
Fig. 29. Sanguineum Subseries (R. 126)
All photos - R. Henny
The third plant (Fig. 29) has a corolla about half the size of the above plant, but all the flowers are pure black in color. The plant can be in full bloom but remain unnoticed, since the black color blends with the shadows of the plant during sunny weather, and on dull days the bloom can not be seen at a glance. On picking the bloom and holding it up to the sun, only the faintest hint of dark red is perceived. To date this is the darkest rhododendron that has come to my attention, and was collected under sanguineum (R. 126).