Phragmipediums or American Slipper Orchids are spectacular orchids. They have unusual big flowers, some of them considered largest within Orchidaceae family (secondly after Paphiopedilum sanderianum, Phragmipedium caudatum has longest petals, which continue growing after flower opening). They are sympodial epiphytes, lithophytes and terrestrials, some of them (Phragmipedium longifolium, Phragmipedium ecuadorense, Phragmipedium pearcei and Phragmipedium klotscheyanum) can even tolerate swampy conditions, as they grow submerged for rainy periods of tropical climates. They have no particular flowering season, some of them tend to flower in spring time, some of them grow and flower better in fall as temperature drops to more comfortable value, and some species tend to flower year-round. Flowers may be in different shades of green, white, brown, red, orange and purple. Leaves are mostly long (up to one meter long) and monotone-green, there are no spotted-leaved Phragmipediums. Though they resemble their close relatives Paphiopedilums (Asian Slipper Orchids), they have rather different growing conditions and require different light, watering, and fertilizers. There are some lovely interspecific hybrids within Phragmipedium genus, as well as some extremely rare hybrids with Paphiopedilums. Phragmipediums are considered more difficult to care, if you orchid beginner, it’s better to start your introduction to Slipper Orchids from Paphiopedilum genus.
There is no one opinion about Phragmipedium systematic, from author to author it would be different number of sections or even species within Phragmipedium genus. Another problem with Phragmipedium systematic is newly discovered species such as lovely orange-red Phragmipedium besseae, discovered in Peru in 1981 and undisputed idol of Slipper Orchids Phragmipedium kovachii, discovered only in 2002. Number of species varies from 15 to 37, because some authors tend to divide species. One of mainstream classification divides genus to six sections: section Phragmipedium (P. caudatum, P. warszewiczianum = syn. P. wallisii, P. popowii, P. exstaminodium, and P. lindenii), section Himantopetalum (P. caricinum, P. christiansenianum, P. pearcei, P. ecuadorense, P. klotzscheanum, P. richteri, P. tetzlaffianum), section Platypetalum (P. lindleyanum, P. kaieteurum, P. sargentianum), section Lorifolia (P. longifolium, P. gracile, P. dariense, P. hincksianum, P. roezlii, P. minutum, P. chapadense, P. hartwegii, P. baderi, P. boissierianum, P. czerwiakowianum, P. reticulatum, P. hirtzii, P. vittatum and P. brasiliensis), section Micropetalum (P. schlimii, P. albiflorum, P. fischeri, P. andreettae, P. besseae, P. flavum, P. dalessandroi), section Schluckebieria with one species Phragmipedium kovachii. But it’s better to remember simple thing: all Phragmipediums could be divided to “dry” and “wet” Phragmipediums, according to their water requirements.
Generally, Phragmipediums need more light than their close relatives Paphiopediums because they dwell in more opened sites of forest, especially epiphytic species such as Phragmipedium caudatum and related species, which need Cattleya light levels to thrive. Unlike Paphiopedilums, most Phragmipedium species are intermediate-temperature orchids and prefer temperatures 70-80 F at day and 50-60 at night, more heat inhibit their grow and could even kill the plant (warm temperatures can cause deadly bacterial and fungal rotting, as plant resistance is reduced due to suboptimal temperatures), however some species such as from section Lorifolia will tolerate intermediate-warm temperatures. Strict temperature requirements is another difficulty with Phragmipedium orchids cultivation, as there are a plenty of warm and hot Paphiopedilums to grow, which suit better to indoor cultivation at a room, without special greenhouses with intermediate temperature regimen. Air humidity should be high – from 50 to 70 degrees, and if high humidity is provided, air moving with fan and so on should be provided too because of high risk of fungal infections. Epiphytic species such as Phragmipedium caudatum could tolerate lower air humidity.
What’s about watering and a potting substrate – it’s different within “dry” and “wet” Phragmipediums. “Dry” Phragmipediums are epiphytic (Phragmipedium caudatum, Phragmipedium wallisii and so on) and require open, well-drained substrates. Best “dry” potting media for Phragmipediums should contain medium grade bark, some tree fern and charcoal and should be watered carefully but roots should never completely dry. “Dry” group comprises from section Phragmipedium, as it contains mostly epiphytic Phragmipediums. And “wet” Phragmipediums need substrates with more water capacity, comprising from sphagnum moss, lava, perlite and some tree fern. It’s better to pot them free and loose, to ensure that roots are well aerated and have a good air supply, and you should ensure that roots of “wet” Phragmipediums never completely dry. Some species as Phragmipedium pearcei grow near rivers and tolerate submersion underwater. “Wet” group contain all terrestrial and lithophytic species, such as Phragmipedium besseae, Phragmipedium schlimii and Phragmipedium kovachii. Other difference from Paphiopedilum genus is that nearly all Phragmipediums (except one species Phragmipedium kovachii) prefer acidic rainwater and don’t tolerate alkaline hard water, which limestone-loving Paphiopedilums prefer. That’s why if you growing Phragmipediums, you should consider this and water them by rainwater, distilled water or reverse-osmosis water. Fertilizers should be applied at half strength because full fertilizer will burn the roots.
What’s about hybrids? There are quite a few lovely hybrids, especially of highly prized Phragmipedium kovachii such as Phragmipedium Eumelia Arias, which is a cross between Phragmipedium kovachii and Phragmipedium schlimii, and other hybrids of section Micropetalum and Lorifolia such as Phragmipedium Cardinale and between sections Micropetalum and Himantopetalum such as Phragmipedium Franz Glanz. Hybrid Phragmipediums are more easy to grow, they do not have such strict growth requirements as species Phragmipediums, they are somewhat intermediate between “wet” and “dry” Phragmipediums and perfectly suited for indoor growing. They also have lovely colorful flowers, especially Phragmipedium kovachii and Phragmipedium besseae hybrids.