Renanthera is a genus of beautiful monopodial orchids from Southeast Asia. There are about 20 recognized species in this genus. Renanthera is a close relative to Vanda. The plants of most species are quite large with stems up to 2 meters, but plants of other species are only several inches in length. Renanthera orchids are epiphytic or sometimes lithophytic evergreen plants.
These orchids are extraordinary beautiful with long inflorescences of gorgeous flowers. For example, Ren. imschootiana produces remarkable inflorescences that can have over a hundred red showy flowers. For most Renantheras, flower coloration is usually warm – red, purple, orange, or yellow with red spots. But some species, Ren. citrine and Ren. annamensis, have white or yellow flowers with purple spots. Renanthera orchids usually tend to bloom in spring or summer.
Renanthera orchid culture is very much similar to the growing conditions for Vanda orchids. All Renanthera species require a lot of bright light to grow well and bloom regularly. If the orchids aren’t provided with sufficient light, leaves tend to grow bigger and become darker. In this case, the plants may look absolutely healthy, however, not blooming at all.
Renanthera orchids do not need a dormancy period for stimulation of flowering, and most species require warm temperature conditions (65-800 F) all year round. However, Renanthera imschootiana and Renanthera storiei belong to a moderate type with the best temperature to grow around 55-650 F in winter and 68-750 F in summer. Like most orchids, Renantheras require the difference of several degrees between night and day temperatures to promote blooming.
Similar to Vanda orchids, most Renanthera species have extremely long roots that are sensitive to rotting, and therefore grow best in open baskets without potting substrate. They can also be planted in pots with bark or other well-aerated potting mixture for orchids, but in this case, the plants should be repotted regularly, at least every 2 years, and watering should be moderate but regular throughout the whole year.
Large Renanthera orchids, like Renanthera imschootiana, are heavy feeders and require balanced orchid fertilizers especially during the active growth period, from March till October. If the plants are kept without potting media, the fertilizers should be applied more frequently – better on a daily basis during the period of active growth.
It is highly recommended to keep these orchids outdoors at least several months a year.