In cultivation the genus Bifrenaria is probably best known for B. harrisoniae, a South American species found in many collections and with a reputation of being difficult to flower. The genus comprises around 24 species, with B. harrisoniae as the type species. It was introduced in 1821 by William Harrison of Rio de Janeiro, Brazil and named after his sister-in-law, Mrs. Arnold Harrison. Described by Hooker in 1825 as Dendrobium harrisoniae, it has also been known as Maxillaria and Colax. Reichenbach transferred the genus to Bifrenaria in 1854.
Bifrenaria tyrianthina was originally described as Lycaste tyrianthina by Loddiges and its flowers could readily be mistaken for those of this genus. B. tyrianthina is reportedly found growing as an epiphyte on trees in the cooler mountains of Rio de Janeiro, Espirito Santo and Sao Paulo in southern Brazil, and as a lithophyte on rocky outcrops in Minas Gerais. These regions experience cool, intermediate conditions with a pronounced dry season, characteristics that define the conditions needed for its successful culture.
The pseudobulbs of B. tyrianthina are four-angled (tetragonal) with a single large, tough leaf 30 cm long and 8-10 cm wide. The pseudobulbs, which are about 10 cm tall, tend to cluster together with the flower scapes emerging from the base of the bulb, sometimes with two scapes per bulb. Flowering in early summer, each scape usually carries two to three attractive violet-purple, long lasting blooms of medium size.
Cultivation of B. tyrianthina requires either a pot or a basket, with a free-draining, coarse bark potting mixture. B. tyrianthina can also be grown on a mount; however it is more difficult to provide sufficient water during summer when the pseudobulbs are developing. Cool to intermediate conditions are adequate and a cool glasshouse or enclosed area helps to maintain humidity, especially in summer. While B. tyrianthina is tolerant of wide temperature variations, good bright light throughout the year and a winter rest appear to be the keys to successful flowering this species.
David Banks (Editor of the Australian Orchid Review) registered the hybrid between Bifrenaria harrisoniae and B. tyrianthina as Bifrenaria Outland in 1992. In my experience, it seems to be easier to flower than either of its parents.