Japan’s dark, wet southern woodlands are host to an odd saprophytic orchid, Epipogium roseum. Despite its name this plant appears pure white when encountered, so I call it the “ghost orchid” of Japan. In truth this achlorophyllous herb (lacking chlorophyll) is a far ranging species, found throughout much of the southern hemisphere except South America.
Epipogium roseum sends up a leafless, crystalline white flower stalk that arises to the height of 15-40 cm by early summer. The flower buds form in a slightly hanging cluster at the apex of the stalk (not unlike Calanthe reflexa) initially, but as it elongates the flowers are presented alternately along the perfectly straight scape. These are pure white, cupped, downward hanging, and about 1 cm long. The sepals and petals are elongate and look similar to each other. The lip is broader and a little frilled, but remains mostly cupped and inconspicuous. Close inspection shows the it has a few purple speckles on it, yet hardly worthy of the name roseum. The flower stem and the flower’s ovaries have a slight yellow brown color, but the overall impression is of a totally white plant. Pods form rapidly after the flowers have opened perhaps hinting at self pollination (autogamy). Being a saprophytic plant (or more exactly, an ectoparasite) it bears no leaves and has no noticeable green color.
It is found in moist woodlands in moderate to deep shade. Some sources state that it is commonly seen growing in compost heaps and that is exactly where I first found the plant. In Japan it occurs as far north as the central Honshu coast to Chiba and Kanagawa Prefectures (Miura Peninsula), and southward to Shikoku, Kyushu, Okinawa and its surrounding islands. It is definitely a more tropical species, being found from Taiwan to southeast Asia including Malaysia, Melanesia, southern China, Vietnam, Thailand, and India. Surprisingly it is also reported from Australia, New Zealand, and almost beyond expectation, in east Africa (Kenya). Likely it is found throughout East Indies as well.
I first found this species most unexpectedly growing on the verge of someone’s garden. Nearby several plants were growing out of a compost pile, and in the surrounding woodland were many more plants. The most notable aspect of this plant is that it has no obvious color in spite of its epithet, roseum. The lower stem can have a bit of yellow brown, but that is hardly noticeable at first glance. The clear white stems, buds, and flowers also belie a translucence on close inspection.
Japan is this species’ northern outpost, up to central Honshu, but otherwise appears to be mostly a denizen of subtropical and tropical forests throughout southern Asia. The plant grows from a subterranean tuber-like root. The flowers only superficially open, remaining strongly cupped and generally face downward. Though not a real beauty, is is an interesting species. It is said to be rather rare throughout its range, or at least is under reported.
Like other saprophytic orchids, it defies normal cultivation due to its dependency on specific soil conditions. All orchids start their lives dependent on specific soil fungi for sustenance, but this species continues that relationship throughout its life. The orchid’s roots are in direct connection with the fungi which in turn are either using dead organic matter in the soil as a nutrient source or the roots of other plants. Hence, saprophytic orchids are now considered to be ecto (outside) parasites (living off another organism’s energy directly). The orchid lives off the fungus, and the fungus lives off dead organic matter or living plant tissues (commonly roots). Yagame, et.al (2007) reports success in growing this species along with its fungal symbiont in vitro. In this study protocorms formed stolons and these in turn gave rise to tubers. The tubers then produced flower stalks. Now that’s interesting!
This certainly is a curious terrestrial orchid, but not one most people are likely to encounter personally. I feel lucky to have seen them myself, having only stumbled upon that one colony. I’ve gone back in subsequent years, but haven’t seen them again. It seems that they can spend many years underground waiting for the perfect conditions to flower and set seed.