Anyone who grew up in the northern part of the USA is familiar with lady slipper orchids. As a child I was introduced to this group of plants when I came upon the moccasin flower, Cypripedium acaule, growing in the local woods of southern New York. Little did I know at the time that this species was just one member of a much larger group of plants known as the slipper orchids, subfamily Cypripedioideae. Nor did I realize they are some of the most primitive of the orchid family, so much so that some authorities have considered them a separate family of plants altogether.
Variation within this subfamily is broad in many regards. They can be found growing in a wide range of habitats, from grasslands, to temperate forests, tropical and subtropical forests, and wetlands such as bogs or seepage slopes. Some are completely terrestrial, while others are epiphytic. Both life cycle and habit too are highly varied. Most are evergreen with the exception of the genus Cypripedium which is deciduous, however, as if to prove the variation of these plants, one species, C. subtropicum, is evergreen. The habit of the leaves and the flower scape as well ranges far and wide, though all are sympodial plants, throwing new growths along a trailing rhizome.
So what makes them all slipper orchids? Mostly the characteristics of the flower. The most obvious common feature is the sac shaped lip, giving these plants their common name. Few other orchids have this feature, and none so developed. Moreover, the flower is graced with a staminode – a sterile, shield shaped stamen that covers the two fertile anthers as well as the stigmatic surface. The lip acts as a temporary trap for insects designed such that escape puts them in contact with the staminode, thus increasing the chance of pollination. A few species of Cypripedium are autogamous – self fertilizing.
Another feature common to most species is that the two lower sepals are fused into a single unit called the synsepal. Occasionally, these sepals are not fused, but that is the exception rather than the norm. The remaining sepal is known as the dorsal sepal and often is rather large. The petals are usually held laterally in most species, and in many are the longest flower parts. They frequently hang down, particularly in the genera Phragmipedium and Cypripedium, though certain sections within Paphiopedium have this feature as well.
Five genera are currently recognized. They are as follows:
Cypripedium – this terrestrial genus composed of around 45-47 species is mostly found throughout the northern temperate regions of the world, but outlying species in Central America and southern China fall within subtropical or even tropical climates. They are deciduous in habit and largely woodland plants. Their cultivation is somewhat problematic. As fate would have it, they also are my favorite slipper orchids.
Mexipedium – a single dwarf species is known from Oaxaca, Mexico, M. xerophyticum. This lithophytic plant likes a bit more water in cultivation than its name implies.
Phragmipedium – this tropical American genus numbering around 15-20 species is known for its love of water. Species range from epiphytic, to lithophytic, to terrestrial in habit. It is composed of six sections. The most astounding species to be found recently, P. kovachii, is in a section all its own.
Paphiopedilum – this is by far the most varied group of slipper orchids, containing 80 or so known species, and is found only in southeast Asia and the East Indies. Five subgenera, 15 sections, and 4 subsections can be found within this diverse genus. They range from true epiphytes, to lithophytes, to terrestrial in habit. Most are found within the bounds of truly tropical areas, but some members of the subgenus Parvisepalum venture into distinctly temperate climes. This genus is the most widely grown and hybridized of all slipper orchids.
Selenipedium – an odd group of highly primitive plants, numbering only six species in all, and all confined to northern South America and Panama. Little is known about their culture outside their native lands. Most are quite tall, leafy plants, with relatively small flowers. Curiosities, but never likely to be important in the horticultural trade.
Cypripedium japonicum is a widespread terrestrial orchid species in Japan, found from all four of its main islands – Kyushu and Shikoku in the south, the largest island, Honshu, and Hokkaido in the north. In olden times massive colonies dotted mountain forests, each being literally thousands of flowering stems strong. Nowadays, colonies are far fewer in number and largely protected and cared for. Out of all those innumerable plants that once graced the wet woods of Japan, a few were pure white flowers – the true alba variety of this species. A few still remain, but virtually all in cultivation these days. It is said that at least two known groups of this rare variety hail from Japan – one from the Nagano area of Honshu and the other from Shikoku. These alba plants are indistinguishable from the typical one except that the flower is completely free of any purple or pink coloring. They lack the anthocyanin pigments that normal flowers have in abundance.
Usually, I am not that drawn to true alba flowers, but in the case of this species, I take exception. Without a doubt this is one of the most elegant white flowered Cypripediums in the world.
As with many alba flowering plants, these do indeed seem to be weaker in cultivation that the normal type. In my experience they don’t hold up as well, being more given to rots. Beyond that, their requirements are the same as normal Cypripedium japonicum – a shady spot in the garden, a rich, humusy loam soil, and plenty of moisture year round. This species is completely intolerant of drying any time of the year. The same could be said for just about any Cypripedium, but with this one it is absolute – if you let them dry out, they will go dormant, weaken, and perhaps die. They are strong feeders, though I would fertilize only with annual addition of organic matter rather than inorganic salt based fertilizer, particularly if you are growing them in a highly organic compost to being with. It is all too easy to over fertilize terrestrial orchids, and they usually reward you by dying outright.
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.
I have been growing lady slipper orchids, genus Cypripedium (here after called Cyps), in a warm temperate climate for 7 years in southern Japan (latitude 34 N). In the spring, when the plants are emerging and flowering, I get a jolt of shear joy – mission accomplished. Then, in June, the monsoon rains kick in and the rotting begins. Bugs get more active and slugs are a constant threat.
By late July (as I write this), I am positively sure that all is lost for the season since just about everything is worn, torn, ripped, rotted or eaten. The oven heat of August and September seems to only emphasize the point – growing Cyps in a hot summer climate is madness. Come November, with its cool rains and falling maple leaves, I dare to check the plants and am often surprised with what not only endured, but even grew well that year. The following article is the method I’ve worked out over the years to grow these lovely terrestrial orchids.
First of all, let me explain the climate I’m working with. Kyushu, the southernmost main island of Japan, is a warm temperate climate sitting on the eves of the subtropics. A typical day in January has a high around 7 C (44.5 F) and a low of 2 C (35.6 F), with an daily average around 5 C (41 F). Why spend so much time worrying average temperatures? The reason is simple – to vernalize adequately (have a proper dormancy period), most Cyps require at least 3 months of an average temperature at or below 5 C. My town, situated just on the edge of a mountain range, barely fulfills that requirement. In fact, the average temperature is a bit warm in the winter months.
If winter weren’t trouble enough, June and July create more problems. This is due to the inordinate rainfall of the summer monsoon. A meter or more of it can fall in just 6 weeks, something most Cyps don’t enjoy. In mid July the rains stop and the oven turns on. Average highs are in the low 30s C (90-92 F) with lows only down to the upper 20s C (80-82 F). Fall comes late, with October drying off and slowly cooling off, but the true colder nights don’t come until late November or early December.
Two very beautiful Cypripediums hail from east Asia – C. japonicum and C. formosanum – and are the only members of the genus from the section Flabellinervia. Considered by most taxonomists to be distinct, C. formosanum is so closely related to C. japonicum that some believe it to be a variety of its larger cousin. They are different in regard to stature, flower color and shape, and importantly, ease of culture. Having grown these plants for the past 7 years, I have experience in their needs and tolerances in the garden. Let’s have a look at C. formosanum first.
C. formosanum is endemic to the higher elevations of Taiwan’s central mountains where it is has become very rare due to collecting pressure. Thankfully, it is a pretty easy species in the garden and a natural clumper. Due to its restricted range, it most likely is a relic population and derived from the more widespread C. japonicum. Despite the fact that its distribution straddles the Tropic of Cancer, it is in fact a temperate plant given that it grows only at high altitude in its native range (2000-3000 meters).
This species is a deciduous terrestrial herb. Its two broad fan-like, pleated leaves grow opposed to each other at the center of a lightly pubescent stem, and are up to 15 cm across each. The stem continues on to support one flower and its floral bract with the total height ranging between 14-25 cm. The flower has an inflated lip with an oval, almost barbed orifice at its front. The slipper-shaped flowers have a pink base color throughout with darker purple-pink spots and mottling. These form striations within the lip orifice and are also more concentrated at the base of the petals and dorsal sepal. The petals are quite broad and the lip has an inflated, puffy look. The staminode (a shield shaped structure covering and attached to the column) is a deep reddish-purple color. Pure white forms exist and are as rare as hen’s teeth.
The plants grow from long stoloniferous rhizomes with new growths being up to 10 cm or so from the previous year’s growth (this section of rhizome is called the internode). At the base of each growth at the point of attachment to the rhizome (the node) are a clump of short, branch less roots (10-20 cm long). The rhizomes themselves are often branching and in time plants can form large continuous colonies over wide areas. Continue reading “Two sister Cypripediums from Asia, C. japonicum and C. formosanum”