The genus Platanthera is well known for its lovely fringed flowered species such as P. ciliaris and the wildly showy P. grandiflora, both from eastern North America. However, a number of species are just the opposite – small flowered and white to green in color. Southern Japan is home to such a species, P. minor, who’s leaves are far more showy then the flowers themselves.
Platanthera minor is a deciduous woodland terrestrial orchid. It is a fairly small plant with broad bluish green, glossy, finely veined leaves that are rib-less; 6-15 cm long and 2-5 cm wide. They are born on a thick fleshy stem in a lose spiral, 3 to 7 in all, and becoming smaller, eventually ending as floral bracts as they ascend the flower stalk. Sterile plants mostly bear a single, broad leaf with no significant above ground stem showing. These smaller leaves are also unique in that they are more rounded at the ends than the leaves of flowering plants, a trait common to other species of this genus. These do not necessarily represent juvenile plants, but may rather be adults “taking a rest” from a heavy flowering/seeding cycle.
The flower stalk grows to a height of 10-25 cm and bears anywhere from 4 to 15 buds each with an accompanying bract that is very large in proportion to the buds themselves. The small greenish-white flowers have an interesting insect-like shape and open sometime in mid July. The light green dorsal sepal and petals form a small cupped hood in which the column is cradled. Two brown pollina contrast strongly with the white column and the downward pointing and backward recurving white lip (which actually looks like a tongue). The remaining sepals are held laterally and curve upward giving the appearance of wings flapping. The spur is long and points backward away from the flower. This strange little flower is not more than a couple centimeters across.
It can be found in the warmer parts of Japan (central Honshu and south to Shikoku, and Kyushu), as well as parts of China, Korea, and Taiwan. On Kyushu it is relatively common in moist forests growing on gentle to severe slopes, but also on ridge lines, from near sea-level to moderate elevations (~50-700 m). Plants occur in small colonies, with few flowering individuals (usually less than 10% of the plants in any given group).
For several years I saw this plant growing here and there on low to moderate size mountains over a large geographical area. Every time I attempted to get pictures of the flowers I was thwarted. I was either there too early, too late, the flower stalks had died, or the plants just “disappeared”. There was a clump that I found just 10 minutes from my house, but I could not find the plant the following year no matter how long I looked. If that weren’t bad enough, the depths of summer’s heat is when this plant flowers, a time when the mosquitoes will will happily cart you away. Talk about frustrating! Finally, in July 2007 I got a shot of a plant in flower, albeit a rather unremarkable specimen.
The flowers are far from showy, nevertheless they have an interesting insect-like look. Plants are never numerous, but rather are always seen in small, isolated groups. The leaves are unmistakably of an orchid, very broad, and shiny. The bracts on the flower stalk also are quite large, dwarfing the little green buds. This definitely is not a beauty, but rather an interesting part of the local flora.
The genus name, Platanthera, means “broad flower” from the Greek words platy = broad or flat, and the feminine of antheros = flower, anthera. The specific epithet, minor simply means “small”. Anyone who is a bird enthusiast knows that a LGB is a “little grey bird” – well, in the terrestrial orchid world there is an equivalent designation, a LGF, or “little green flower”. This species qualifies for that moniker in spades. Its Japanese name, oobanotonbosou comes from the words ooba = big leaf, tonbo = dragonfly, and sou = plant, meaning “big leaf dragonfly plant” because the leaves are broad and conspicuous and the flowers look something like a dragonfly, if you are lucky enough to see some!
I would guess someone here in Japan has tried this plant in culture before. It probably can be grown like other Platanthera species, but a bit drier than most. Unlike many in the genus, this is not a bog plant, but always is seen on moderate to severe slopes where drainage is excellent. It should respond well to any free draining compost rich in organics and moderately acidic in reaction. It is not likely to be more cold hardy than USDA zone 7 however.
Here’s another odd little orchid from Japan. I cannot recommend it in cultivation simply because it doesn’t warrant much attention as a garden plant. Beyond that, I’m sure sourcing one outside its native range would be difficult. It will likely remain a little unknown inhabitant of Japan’s warm temperate forests.