The slipper orchids are not likely to be confused with any others; with the exception of a single species, all the members of the subfamily Cypripedioideae have the lip or labellum modified into a pouch, an inflated bag-shaped organ. If you can imagine a dainty foot nestled in this pouch, you’ll comprehend these orchids’ charming familiar designation as “lady’s slippers.”
The highly pragmatic purpose of the pouch, however, is to lure an insect, entrap it, and force it to leave the flower with a load of pollen. The uppermost sepal (the dorsal) is enlarged and conspicuous. The other two sepals are fused and are called a synsepalum; located at the bottom of the flower, the synsepalum is often hidden by the pouch. Two of the petals extend laterally and the third is the pouch.
The flowers are generally waxy and thick textured, lasting well both on the plant and when to cut. The leaves are strap-shaped and either plain green or mottled (tessellated). They arise as fan-shaped growths from the rhizome and live for many years, though they flower only once. Old plants can have many growths and produce many flowers. The flower stalks emerge from the center of the new growths; those most commonly grown bear a single flower, though some species bear more.
Cypripedium, paphiopedilum, Phragmipedium, and Selenipedium are the four genera in the subfamily. Of these, Selenipedium is of little horticultural interest; the plants are large and the flowers generally insignificant. Cold-winter-climate orchid fanciers and wildflower enthusiasts alike would like to grow cypripediums, but they are difficult both to propagate and to grow.
Paphiopedilum is a favorite of orchid fanciers. At one time all the slipper orchids were called Cypripedium, and a slowly diminishing group of fanciers continues to call the paphiopedilums Cypripedium, or cyps (pronounced sips) for short. The more up-to-date call them paphs.
All of these are Old World orchids, native from the Himalayas to Taiwan and eastward to New Guinea and the Solomon Islands. Most cultivated slipper orchids belong to this genus. The tropical New World slipper orchids in Phragmipedium are less widely grown, but interest in that genus is increasing.
Most slipper orchids thrive given nighttime temperatures of 60° to 65°F (16° to 18°C), considered an intermediate range for paphiopedilums. The warm growing slipper orchids require nighttime temperatures of 65° to 70°F (18° to 21°C); some cool growers prefer 55° to 60°F (13° to 16°C). Daytime temperatures should be around 20°F (11°C) warmer. If daytime temperatures exceed 90°F (32°C), provide shade as well as increased humidity.
All of these orchids are shade lovers, but they differ in the degree of shade preferred. Most thrive given about 1,000 foot-candles of light. These preferences and their low stature make them favorites for growing indoors, either at windows or under artificial lights.
Paphiopedilums grow in a range from sea level (sometimes even within reach of salt spray) to high, cool, moist mountains. Some make their home in trees, but most are terrestrial, growing in moss and leaf mold on rocks or on banks where seepage keeps them supplied with moisture.
Because they lack pseudobulbs in which to store moisture, their roots must never go completely dry. They also require air around their roots, so the planting mix should be porous. Commercial mixes are available, but fine- or medium grade fir bark mixed with perlite and peat may be used. Hard water containing calcium carbonate is not harmful, but water containing sodium and other salts can be fatal. Never water late in the day; water standing in the fans at night encourages decay.
These slipper orchids need repotting every 2 or 3 years, as the potting mix breaks down and becomes less porous. Repotting is best done after bloom. Remove the old mix and replace it with a moistened new mix, packing it carefully but firmly around the roots. The leaf fan should rest on the surface of the mix. Water only lightly until new growth begins; then resume regular watering. If plants are very large, they may be divided at repotting: cut or break them into divisions of at least three fans each.
Feed with a half-strength solution of liquid fertilizer every week during spring and summer, and every other week during the winter months.
The genus paphiopedilum consists of roughly 70 species and named selections have been made from many of these. Hundreds of primary crosses (crosses between two species) exist, and the number of complex crosses (those with three or more species in their ancestry) is legion.
Keep in mind when buying a slipper orchid that plants are sold either as divisions or as seedlings. Divisions of mature plants will exactly resemble the parent whereas seedlings will resemble it more or less. The few species and hybrid types it is possible to describe here favor intermediate temperatures and light unless otherwise noted.
- Paphiopedilum argus
- The leaves are tessellated, and the 12- to 18-inch scape carries a single 5-inch flower. The white dorsal has green stripes and purple spots. Wavy-edged petals are white blushed with pink, veined in green, and lavishly sprinkled with blackish purple spots. The pouch is green and brown. It blooms midwinter to spring.
- Paphiopedilum armeniacum
- A rambling rhizome produces well-spaced clumps of boldly mottled 4-inch leaves. The 9- to 10-inch flower stalk bears a single pale to bright yellow 4-inch flower with a small dorsal sepal and a large lip with faint red markings near the mouth. It grows best in intermediate to warm conditions. Grow it in a basket of slats or wire mesh to accommodate the running rhizome. Spring or summer bloom.
- Paphiopedilum barbatum
- Clumps of tessellated leaves produces 12- to 14-inch stalks bearing one or two 4-inch flowers. The large dorsal is white, with green and purple stripes. Slightly drooping maroon petals have blackish purple warts. The pouch is purple. Blooms in early winter, sometimes re-blooming in spring.
- Paphiopedilum bellatulum
- This dwarfish plant has strongly mottled leaves and a flower stalk that holds the nearly round flower just 1 1/2 to 3 inches above the foliage. The flower is white, finely sprinkled with spots and blotches of maroon; its small pouch is the same color. The dorsal sepal and petals are nearly round. This intermediate to warm grower likes both night temperatures and brightness in the higher ranges and needs excellent drainage. A midwinter rest, with slightly less water and at slightly lower temperatures, will induce summer to fall bloom. Paphiopedilum concolor; P godefroyae, and P. niveum are all similar in appearance and requirements.
- Paphiopedilum callosum
- Resembles P. barbatum, but with more intense pinkish tones in the petals and pouch. Blooms early spring through autumn.
- Paphiopedilum charlesworthii
- The 4-inch flower rises above the green foliage clump on a 6-inch stalk. The very large dorsal sepal is pink, with deeper pink veining and a narrow white rim. The smaller petals and pouch are brownishly flushed with pink. Autumn bloom.
- Paphiopedilum delenatii
- Dark green 4-inch leaves are marked above with paler green and below with purple. The clumps are spaced out along a rambling rhizome. The 9-inch flower stalk produces one and sometimes two 4-inch pale pink to white flowers with a pink pouch. This species blooms in spring.
- Paphiopedilum druryi
- Long rhizomes produce scattered clumps of 6- to 18-inch light green leaves and 10-inch flower stalks bearing a single, nearly 4-inch, yellow to greenish flower with a bold purple stripe on each petal and on the dorsal sepal. This intermediate grower blooms in late winter and early spring and likes strong, indirect light and warm days coupled with cool nights.
- Paphiopedilum fairrieanum
- The leaves are green, sometimes faintly tessellated. The 5- to 18-inch flower stalk bears a single flower 4 inches tall and somewhat narrower. The tall dorsal sepal has frilled edges and is white, heavily marked with green and purple stripes. The similarly colored petals droop for two-thirds of their length, then turn sharply upward, giving the flower a somewhat whimsical aspect. Colors can vary from white and green to white and deep purple. An intermediate to cool grower, it blooms in late fall and early winter.
- Paphiopedilum haynaldianum
- Yellowish green, large leaves surround flower stems that can reach 20 inches and carry two to four 5- inch flowers. The dorsal sepal is narrow at the base and white with purple stripes in the lower half; it has a sprinkling of maroon spots. The narrow, widely spreading petals are yellowish green heavily marked with maroon spots near the base. The large pouch is greenish tan with dark green veins. Bloom occurs in late winter and spring.
- Paphiopedilum henryanum
- The leaves are somewhat more than 6 inches long, plain green with some purple suffusion underneath. The 6-inch flower stem carries a single 3-inch flower having a yellow dorsal heavily marked in dark purple with deep pink petals and lip. This species blooms in winter to early spring.
- Paphiopedilum insigne
- This widely grown and variable species has plain green leaves and a 9-inch stalk bearing a single 5-inch flower. The dorsal sepal is yellowish green or pale green with a white edge and raised spots of purple or brown. The narrow petals are yellowish green to yellowish brown. The flower has a high gloss. Plants are hardy to almost 32°F (O°C) but intolerant of protracted warmth. Bloom period is fall and early winter.
- Paphiopedilum javanicum
- The leaves are sparingly tessellated, and flower stalks 6 to 14 inches tall carry a single 4-inch flower. Its dorsal sepal is narrow and greenish white, striped green and with a sharp white tip. Narrow, spreading petals are green with purple tips. Bloom season is irregular, but usually in summer.
- Paphiopedilum malipoense
- The 4- to 8-inch leaves are boldly mottled. The 10-inch flower stalk carries a single 3-inch flower whose dorsal sepal and petals are green marked with faint purple lines. The large, baggy pouch is somewhat translucent and stained pink by profuse maroon dotting inside. A warm grower, it blooms in fall and winter. Grow it in a basket of slats or wire mesh to accommodate the running rhizome.
- Paphiopedilum micranthum
- As in P. armeniacum, the foliage clumps are spaced along a wandering rhizome. The leaves are 2 to 6 inches long and dark green mottled in lighter green. The 3- to 8-inch flower stalk carries a single 3-inch-wide flower with a short, nearly round dorsal and petals or greenish yellow marked with purplish pink lines. The very large, puffy lip is 3 inches long and pink. This is an intermediate to warm grower.
- Paphiopedilum spiceranum
- Clumps of green leaves produce 10-inch arching flower stalks that carry a single 3-inch flower. The large white dorsal sepal is narrow at the base, then spreads upward and folds back to emulate a small calla (Zantedeschia). A maroon vertical streak decorates the front. Petals are yellowish green suffused with brown, and the margins near the flower center are deeply crimped. This intermediate to cool grower blooms in autumn and early winter.
- Paphiopedilum sukhakulii
- Clumps of tessellated leaves produce 10-inch stems bearing a single 5-inch flower. The dorsal sepal is white with a fine striping of green. The horizontally spreading petals are green, heavily spotted with blackish purple. Bloom is in autumn, sometimes also in spring. This species has been a parent to many fine hybrids.
- Paphiopedilum superbiens
- The 6- to 10-inch leaves are strongly mottled. The 6- to 10-inch flower stalk carries a single 5-inch flower with a broad, sharply pointed dorsal of white flushed pink and heavily streaked with green and purple veins. Long, narrow, downwardly angled petals shade from green at the base to purple toward the tips. The glossy lip is dark maroon and 2 1/2 inches long. This intermediate grower blooms in summer.
- Paphiopedilum venustum
- Heavily tessellated leaf clumps give rise to 5- to 10-inch flower stalks carrying a single 5-inch flower. The low, broad sepal is white, heavily striped in dark-green. The petals are greenish white with green veins; their outer third is copper or purple. The lip is yellow or coppery with strong green veining. Bloom is in winter.
Several species of paphiopedilum have flower stalks that carry from 2 to (rarely) 20 flowers. This typically open sequentially-one fading and falling as the next opens-but some have several flowers open at a time. These are not the easiest plants to grow, and beginners are urged to gain experience before attempting them.
- Paphiopedilum glanduliferum (P. praestans)
- Dark green leaves are 14 to 16 inches long. The 12- to 20-inch flower stalk carries from two to five flowers. The tall, narrow dorsal is 2 inches long and half as wide, yellow with pronounced purple stripes. The lower sepals are similar. Narrow petals angle downward at a 45° angle; they are yellow veined with maroon and are fringed at the edge. The lip is 2 inches long or more, yellow marked with maroon. It blooms in summer.
- Paphiopedilum glaucophyllum
- The leaves are 12 to 20 inches long and either green or faintly mottled. The flower stalk can reach 2 feet and produce up to 20 flowers usually one at a time, rarely two. The flowers have a broad cream to green dorsal heavily spotted and striped with purple. Petals are 1 1/2 to 2 inches long and white, with many deep pink to maroon spots as well as tufts of short hairs along the edges. The lip or pouch is 1 1/2 inches long and pink finely stippled with maroon. The variety P. g. moquettianum is slightly larger, and the dorsal is speckled rather than veined. It blooms in summer or at any time and is a warm grower.
- Paphiopedilum philippinense
- Clumps of dark green 6- to 20-inch leaves produce flowering stems to 20 inches, each bearing two to five flowers. Both the dorsal sepal and the fused lower sepals are 2 inches long, white striped with maroon. Petals are narrow, yellow at the base fading to maroon. They are somewhat drooping, twisted, narrow, and up to 5 inches long. This species blooms in late winter or spring bloom.
- Paphiopedilum rothschildianum
- This spectacular species is slow to reach blooming age after division and seems to resent transplanting. Its dark green leaves can reach 2 feet in length, and the 18-inch flower stalk carries from two to four flowers with a petal span of up to 10 inches. The 2 1/2-inch-long dorsal sepal is cream, green, or yellow. The long, narrow petals are yellow or cream striped with maroon, the pouch tawny or yellowish suffused with dark red. Bloom is in late spring or early summer.
- Paphiopedilum sanderianum
- The dark green, strap-like leaves are 12 to 18 inches long. The flower stalk is 18 inches tall and carries two to five flowers. The 2 1/2-inch dorsal sepal is yellow, striped in deep maroon. Narrow, twisting, drooping petals are 12 to 36 inches long, yellow at the base with maroon spots and becoming deep maroon in their last three-quarters. This species is rare and expensive.
- Paphiopedilum stonei
- The leaves can reach 28 inches in length, and the flower stem can reach 28 inches; it bears two to four large flowers. The dorsal sepal is broadly oval, 2 inches tall and wide, and white with a few dark purple vertical lines. The petals arch out and down and are yellow, dotted and flushed in maroon. The lip is creamy or white at the base, deep pink toward the front. It blooms in late summer or early autumn.
- Paphiopedilum victoria-mariae
- Heavily mottled leaves are 10 to 12 inches long. The flowering spike can reach 3 to 4 feet in height and must be staked. It elongates as flowering progress, usually one bloom at a time, to a total of 20 blooms or more. Each flower has a 1-inch dorsal of cream or yellow with a green center striped with maroon. The 1 1/2-inch petals are narrow, twisted, and reddish purple; the 1 1/2 -inch lip is purple with a whitish or greenish rim. There is a long bloom season beginning in spring or summer.
You are more likely to encounter hybrids than you are the species paphs. Many are first-generation crosses between two species, but much, much more are complex hybrids-hybrids of hybrids, sometimes involving multiple remote ancestral species. The orchid plant you buy may be a seedling, in which case it will bear a grex name. Grexes guarantee only a greater or lesser resemblance to other seedlings from the same cross. On the other hand, if your plant is a division, it will be more expensive but identical to its parent. For instance, you will come across many plants named Winston Churchill, a grex name. But if you see Winston Churchill ‘Indomitable’, it will be a division of an award-winning plant, not just a relative. New hybrids appear at a frantic pace. During 3 months in a recent year, 80 new hybrid paphs were registered. All tend to be sturdy plants with broad, rounded flowers having clearly defined colors and a high gloss. Here are a few of the countless hybrid grexes.
- Paphiopedilum Harrisianum
- This, the first hybrid paphiopedilum, dates from 1866. Flowers tend to dark burgundy red, faintly striped with white in the dorsal sepal.
- Paphiopedilum Makuli
- These flowers have white dorsals striped in green and purple, pale petals spotted with maroon and russet red pouches.
- Paphiopedilum Maudiae
- These plants bear tessellated leaves and sturdy stalks holding white flowers with green striping. Later crosses involving darker forms of the original species have yielded plants of similar vigor and striping, but in pink (coloratum) and dark red (vinicolor) shades.
- Paphiopedilum Winston Churchill
- Large, well-rounded flowers of heavy texture characterize this grex. Dorsals are big and broad, white, and heavily spotted or flared with deep red.
Tropical American Slippers
Members of the Central and South American genus Phragmipedium have not enjoyed the popularity of paphiopedilum, but interest in them and their hybrids have been rising rapidly since the introduction of the bright red Phragmipedium besseae. These plants superficially resemble those of the Asiatic slippers, as do their flowers, but there are significant differences. The flower stem is jointed, has conspicuous bracts, may be branched, and normally bears many flowers. Chromosomal differences between the two make intergeneric crossing very difficult. Although both genera are alike culturally, there is one significant difference: Phragmipedium is strongly acid-loving, so cannot tolerate lime or hard water.
- Phragmipedium besseae
- This orchid was discovered only in 1981-rather a marvel, considering its bright color. The dark green foliage clump sends up a bloom stalk that bears from one to six flowers that open in succession. The flowers measure a bit less than 2 1/2 inches wide and 2 inches high. All their segments, including the pouch, are bright red. Recent seedlings and hybrids have shown color variations tending toward orange and yellow.
- Phragmipedium caudatum
- Leaves of this spectacular orchid are 2 to 3 feet long. The yard-tall flower stem displays two to four flowers open at one time on individual 6-inch stalks. The dorsal sepal is cream colored, with a netting of maroon to brown or green veins. The long, twisting petals open as much as 6 inches in length and elongate over several days to a possible 36 inches. Petal growth stops if the tips encounter a solid surface, so the plant should be grown in a hanging basket or supported on a pedestal. The petals are initially colored like the dorsal sepal, but toward the tips, the color becomes deep rose or purplish red.
- Phragmipedium klotzscheanum
- These clashing consonants belong to a slipper orchid with narrow, sedge-like leaves 12 to 15 inches long. The flowering stem is 2 feet tall and produces as many as six flowers in succession. The dorsal sepal is 2 inches tall and pale greenish brown striped with maroon. The drooping 4-inch petals display the same color. The pouch is yellow, with a white interior and a speckling of purple.
- Phragmipedium lindleyanum
- The leaves are deep green and 1 1/2 to 2 feet long. The flower spike can be up to a yard tall and bear (one or two at a time) as many as 30 greens and rose flowers with yellow or green lips. The overall flower size is somewhat under 3 inches.
- Phragmipedium pearcei
- The leaves are deep green and 10 to 18 inches long. The two to four 5- inch flowers are green and white with a suffusion of pink. The lip is just over 1 inch long and is green, often with purple dots at the mouth.
- Phragmipedium sargentianum
- The green leaves are yellow edged and up to 1 1/2 feet in length. The tall (possibly 4 feet or more) flower stem carries as many as five flowers, which open in succession and resemble those of P. lindleyanum.
- Phragmipedium schlimii
- The bright green leaves are up to 1 foot long. The branched 1-foot flower stalk produces from two to six flowers. Petals and sepals are broadly rounded and the lip is broad and puffy. The flowers are pink or white, or a combination of the two, and are 2 inches across.