There are 15 species in the genus Promenaea, which was named after the ancient Greek Priestess of Dodonia. The genus, which was established by John Lindley in 1843, belongs to the Tribe Maxillarieae and forms part of the Zygopetalum Alliance; it is endemic to central and southern Brazil. Most Promenaea species occur as epiphytes in moist forests at moderate altitudes but they can sometimes be found growing as lithophytes.
Pabst and Dungs have assigned the various species to three sections within the genus, namely, the Promenaea rollisonii section, the Promenaea xanthina section and the Promenaea stapelioides section:
The Promenaea rollisonii section includes the species P. lentiginosa, P. riograndensis and P. rollisonii. The last-mentioned is sometimes spelt rollinsonii but this is incorrect as the species was named after a prominent nurseryman named Rollison. P. rollisonii, the best known of the three species, has heavily spotted, triangular-shaped flowers. The Promenaea xanthina section includes P. acuminata, P. albescens, P. catharinsensis, P. dusenii, P. fuerstenbergiana, P. guttata, P. malmquistiana, P. microtera, P. ovatiloba, P. paranensis and P. xanthina. The last is easily recognised by its golden-yellow, triangular, partly cupped flowers. The Promenaea stapelioides section currently comprises a single species, Promenaea stapelioides, which bears banded, cupped flowers.
Many of the above species are difficult to obtain in Victoria, and virtually all hybrids available have been derived from only five of them.
The Three Most Common Species
Promenaeas have compact plants with prominent pseudobulbs that often vary in shape, depending on the particular species. All produce an attractive display of flowers that are proportionately large for the size of the plant. P. rollisonii has round, clustered pseudo-bulbs about 25 mm tall, while P. xanthina has four-sided pseudobulbs about 30 mm tall. All species have four grey-green leaves (each about 50 mm long), two emerging from either side of the base of the pseudobulb and two from the apex.
P. stapelioides is found from Rio de Janeiro to Santa Catarina, where it grows on trees or rocks in cool, damp mountains at an altitude of about 1000 m. Its flowers have cream to pale green sepals and petals with deep purple-red stripes; the lip has a purplish-black cushion on its mid-line. Each inflorescence is about 50 mm long and bears one or two flowers about 50 mm across, either in summer or autumn. It may be grown either in a basket or on a slab.
P. xanthina, sometimes also known as P. citrina because of its golden-yellow flowers, is also found in southern Brazil but at an altitude of 1700 m. It also bears one or two flowers per inflorescence, the scented flowers measuring about 40 mm across and being perfumed, heavily textured and long lasting.
P. rollisonii has heavily spotted, pale pink petals and sepals on arching inflorescences. Those of its hybrids sometimes droop over the rim of the pot.
Cultivation. Promenaeas are relatively easy to grow provided as few simple precautions are taken. Warm to intermediate conditions are preferred, as promenaeas will not tolerate frost. They prefer small pots containing a well-drained mix. In his book Growing Orchids, Part 2, J.N. Rentoul lists small bark, coarse gravel, peanut shells, a little charcoal and dry oak leaves as ingredients for a suitable potting mix. Seedlings are often grown in sphagnum moss to which polystyrene foam or Canunda shells may be added. Plants should be re-potted regularly, as they are very susceptible to root rot in decayed potting mixes.
It is essential to provide plenty of water and high humidity during the growing season; the pots must never be allowed to become completely dry. A rest period should be provided at the end of the flowering season. They should be watered with good quality water, preferably daily in summer, reducing to every third day in winter. I apply very weak liquid fertiliser during each watering during the growing and flowering seasons, and add a sprinkling of blood-and-bone fertiliser to the pots after flowering. Periodically flushing the pots with water alone (no fertiliser) is good practice. Take care during the cooler months not to allow water to lie in the new growths, as they rot easily.
While Promenaea species are found in various locations, they are always exposed to high humidity, good air movement and semi-shade in their mountainous habitats. If exposed to too much light, their grey-green leaves soon become grey. Their main pests are snails, slugs and mealy bugs, which are easily controlled with a range of proprietary products.
The following hybrids have been registered:
P. Burgundy Fire, P. Burgundy Glow, P. Burgundy Sparkle, P. Chacaca, P. Carnival, P. Catarina, P. Chameleon, P. Dinah Albright, P. Firefly, P. Florafest Cheetah, P. Florafest Gold, P. Florafest Sparkler, P. Galaxy, P. Glow Worm, P. Gold Dust, P. Golden Sparkle, P. Goldspeck, P. Kiwi Small World, P. Limelight, P. Meadow Gold, P. Michael Wilson, P. Norman Gaunt, P. Olinda, P. Partridge, P. Samsu