Northern and central Japan is home to one of the smallest Cypripedium species, C. debile. Both its Latin and Japanese names allude to this plant’s size – debile – meaning “frail” and koatsumorisou, meaning “small lady slipper”. While is this one won’t ever win a beauty contest, it is an amazing little orchid.
Cypripedium debile is a dwarf herbaceous perennial orchid of moist woodlands. Like its larger cousin, C. japonicum, the two small nearly heart shaped leaves sit atop a short stem that is between 4-8 cm tall. The light green leaves are completely hairless, shiny, and smooth (glaucous). Their venation is simple and the leaf margins are slightly ruffled. Each one is between 3-6 cm long and about as wide. The thin, almost thread-like flower scape is short (2 cm or less) and hangs slightly downward from between the two leaves. The single floral bract is relatively long and grass-like, often longer than the flower stalk itself.
The flower itself truly hangs downward such that the orifice of the lip is either facing strongly in a downward position or in some cases even can face the ground surface directly. The tiny flower is not much to see being only about 1.5-2 cm across. The oval lip is pinkish and lightly veined with purple on the outside, but strongly veined inside. It is obscured by the other flower parts which are very similar is size and shape: the dorsal sepal, the petals, and the synsepal. All are a light green color with slightly darker green veins throughout.
The overall impression is a very shy flower that is hiding its little head between its knees. In nature these can form scattered, yet extensive colonies. The roots are few and short, reportedly growing between layers of leaf humus and are no more than 10 cm long. Plants can form two or three growths, but typically are found singly.
This tiny slipper orchid is found throughout the northern half of Japan from central Honshu to the Tohoku region (locally abundant), and also on Shikoku (Ehime and Kochi Prefectures where it is very rare). It is currently absent in western Japan and Kyushu. Reported also from Korea, Taiwan, and China. In Japan it is said to grow at the edges of deciduous hardwood forests where they meet coniferous forests (hardwood/conifer ecotone).
This Cypripedium, along with the other two members of section Retinervia, is the little shy darling of the genus. What can you say about a plant that under normal circumstances you would probably step on if you weren’t looking closely at you feet? I guess you could say it isn’t much to look at, or at best is a very dainty little thing. Perhaps if the flower were held above the leaves and were more open it would have more decorative value. Definitely its greatest charm are the shiny pair of heart shaped leaves – certainly they are the most conspicuous aspect of the plant. Having said that, if you get down on your belly and look closely, you can appreciate the plant better.
The flower is likely to be pollinated by some kind of fly, hence its strange, hanging position. Nowadays it is becoming more and more rare in Japan because of habitat changes due to forestry practices and to a lesser extent to collection for the horticultural trade. While it can be grown from seed, the vast majority of plants in the trade today are from the wild. Certainly not a beauty, but cute if you are given to loving orchids. To appreciate its tiny stature, take a look at the photo below of a Paphiopedilum malipoense flower in comparison with two full grown C. debile plants – they are about the same size. Now that is a small plant.
This species is a bit of an enigma in cultivation. While it isn’t difficult to grow for a short period, say a couple seasons, it tends to fail over time. I suspect the problem is that it is so small and easily hurt by just about any mishap: not enough water or too much, animals stepping on them, bugs eating them (one slug could eat an entire plant in a few minutes), and so on. Unless you have truly natural woods with native soil (humus layer, a loamy organic layer, and so on) and it is evenly moist without too many extremes, I wouldn’t attempt this one in the ground. Instead, pick an oversized pot, either plastic or glazed clay, but be sure the drainage is perfect.
Unlike most Cyps, this species should be grown in a more organic mix, say 50% leaf mold from deciduous trees (beeches or maples would be best) and 50% perlite or the like. Soil reaction should be acidic, but needn’t be strongly so. Keep the plant well watered, but make sure it doesn’t get soaked either or rots will appear quickly. I would avoid direct watering since this could damage the leaves and invite problems. Humidity must always be high, 60% or better all the time. Fertilize very weakly. Use just a bit once a month while in growth. Keep it out of the rain and strong winds. With luck you may keep it going for a time, but long term this plant is a real challenge to please unless the conditions are exactly to its liking. A delicate species in anyone’s book.
Is this one worth growing? I’d say yes if you are a terrestrial orchid buff or if you have a cool greenhouse designed for “alpine plants” and can maintain exact conditions continuously. Otherwise, you may well be frustrated trying to keep this little novelty alive very long.