Clues to Orchid Identification – Columns

Orchids can be incredibly easy to identify or frustratingly difficult. For instance, the Flying Duck orchid is easily recognizable. The name says it all. But for many other orchids, particularly the ubiquitous blue sun orchids, it is necessary to make careful observations.

Which is which — In this collage there are several species, but which is which?

For sun orchids the most important distinguishing feature will often be the column, details of which are described or illustrated in orchid keys. For example Bates and Weber, Orchids of South Australia (1990) has an illustrated dichotomous keys showing the different types of columns.

As part of the key, drawings of the column were included — Images from Bates & Weber, Orchids of South Australia, pages 147 to 150; courtesy of the Board of the Botanic Gardens and State Herbarium.

With today’s cameras, it is possible to photograph the column, preferably from front, side and above. This helps greatly with identification.

The following photographs illustrate the variety of columns.

Thelymitra X truncata - a natural hybrid — Thelymitra X truncata – a natural hybrid

And it is not only the blue orchids that can be a problem, in South Australia; there are three pink orchids which are different in size and flowering time, features that are not obvious in a photograph, so the column is a helpful identification tool.

Thelymitra luteocilium – has tufted hairy column arms

Thelymitra rubra – has finger-like column arms and no tuft

Thelymitra carnea – has smooth column arms

And just what is the column? It is the reproductive organ of the orchid flower and is unique amongst plants because it is the fusion of the male (stamens) and female (pistil) parts. It is usually found in the centre of the flower and both releases and receives the pollen sac.

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