How Many Species of Rock Orchid Are There?

Range

• Rock orchids are native from Australia' southern coast to tropical regions north of Cairns in Queensland. They grow from sea level to the tops of mountains. Some species grow as lithophytes, meaning plants that grow on rocks, hence their common name. As lithophytes, rock orchids grow in large clumps with their roots forming dense mats on rocks and cliff faces. Other species grow as epiphytes on tree branches in rainforests.

Description

• Rock orchids produce more than 100 creamy yellow-to-white flowers on long racemes that grow on stems that are straight or slowly arch. Purple dots or red veins cover the flower's labellum or lip. Rock orchids grow from two to five thick, leathery leaves. Rock orchids grown from seed can take 6 to 7 years to produce flowers. Some species do not produce flowers for 12 to 14 years. They are tough and tolerate drought and temperatures from near frost to more than 113 degrees F.

Classification Confusion

• The rock orchid is also known by the common names rock lily, king orchid and outstanding dendrobium. All orchid species are susceptible to cross-pollination from other species. This cross-pollination produces hybrid orchids that bear the characteristics of both varieties leading to confusion for correct scientific classification.

Scientific Classification

• The correct scientific names of rock orchids species are evolving so that many names listed in the literature are considered dated. In 2006, Peter B. Adams, J.M. Burke and S.D. Lawson at the University of Melbourne concluded that the following nine species may be accurately classified as Dendrobium speciosum: D. speciosum var. speciosum was first reported in 1804, D. speciosum var. hillii was added in 1877, F.M. Baily reported D. speciosum var. grandiflorum and D. speciosum var. curvicaule in 1898, S.C, Clements reported D. speciosum var. pedunculatum in 1981 and D. speciosum var. capricornicum in 1982, P.B. Adams and his Melbourne colleagues reported D. speciosum var. boreale in 2006 and Adams more recently added D. Speciosum var. blackdownense and D. speciosum var. carnarvonense.