Dendrobium cruentum is a rare south-east Asian species belonging to the section Formosae. The long-lasting flowers are a spectacular contrast of orange-range on the lip with green-white petals and sepals. The extent of orange-red can be variable amongst cultivars, and even from year to year in the same plant. The native range includes Vietnam, Myanmar, and Thailand, but it now thought to be nearly extinct in the wild.
The species is found at lower elevations, and definitely a warm grower. Our plant lives with the Paphiopedilum seedlings, with minimum 62F (17C) nights in winter, and summer nights well into the mid-upper 60s (18-20C). Daytime highs are in the upper 70s (25C) in winter and low 80s (28C) in summer. We grow it mounted, and a bit drier than other tropical Dendrobium. However, humidity is consistently 55-75%.
Dendrobium cruentum has been used extensively in hybridizing, and vigorous hybrids abound, though the actual species is much less common. It is commonly bred with cooler-growing species to ensure a wider temperature tolerance for the hybrids. I have noted a few photographs claiming to be Dendrobium cruentum, but the plants are actually hybrids and backcrosses.
Another southeast Asian species, Dendrobium suzukii, has very similar flowers. It was considered a likely hybrid until recently, when a wild population was rediscovered in 2014 in Vietnam. An easy differentiating characteristic of Dendrobium suzukii from Dendrobium cruentum is the number of keels on the lip: Dendrobium cruentum has 3 (see second photo above) and Dendrobium suzukii has 5. The latter also has a larger flower and a wavy margin on the lip compared to Dendrobium cruentum.
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