A Guide to Orchid Taxonomy

An orchid is a type of a flowering plant or an Angiosperm. Among Angiosperms, there are different species and the largest of them is called the Monocots. Orchids are also a type of Monocot. Other commonly-seen Monocots are corn, rice, wheat, palm trees and lilies. Orchids vary from the other Monocots due to some unique features. These include:

  • Presence of pollen in two large masses
  • Joint stamens and pistils in the form of columns
  • Absence of an endosperm and organized embryos

Understanding Orchid Taxonomy

It is rather difficult to identify all orchid types as nearly 25,000 species of orchids have been identified so far and new ones are still being discovered. The present taxonomical study of orchids and their classification follows a system that was introduced by Robert Louis Dressler. The nomenclature for various genres of orchids is defined by the International Code of Nomenclature of Cultivated Plants and the International Code of Botanical Nomenclature. Orchid classification has been further standardized under the Royal Horticultural Society of London. It registers any new orchid species or hybrids that are discovered. Orchids are now classified as:

  • Kingdom Plantae
  • Phylum Magnoliophyta
  • Class Liliopsida
  • Order Orchidales
  • Family Orchidaceae

Family Orchidaceae or the Orchid Family or Orchidaceae is further subdivided into several subfamilies. Each subfamily is further divided into smaller tribes that are further divided into sub-tribes. The orchid sub-tribes are further grouped under different alliances and respective genera. Though orchid taxonomy continues to engage some debate, contemporary studies agree that there are five main subfamilies along with 22 orchid tribes, 70 sub-tribes and 850 genera. It is important to have a basic knowledge about the five main orchid subfamilies as these are often mentioned when differentiating different orchid types.

1. Subfamily Apostasioideae

  • They are the most primitive form of orchids
  • Characterized by the presence of two-to-three fertile anthers

2. Subfamily Cypripedioideae

  • They are monophyletic, i.e. presence of two fertile anthers
  • Identifying feature — a shield-shaped stamen with a pouch-shaped lip
  • Consist of nearly 115 types of terrestrial orchids

3. Subfamily Orchidoideae

They have a single, fertile anther that stands erect. The Subfamily Spiranthoideae is ususally included as a part of Orchidoideae.

4. Subfamily Epidendroideae

  • The single anthers are identified due to their sub-erect structure, i.e. they tend to grow towards the outer edges
  • Most widespread subfamily represent more than 80% of the orchid species, i.e. more 10,000 types of orchids
  • Subfamily Higher Epidendroideae are now considered a part of Epidendroideae and not a separate entity

The most common species of orchids found in gardens around the world include Phalaenopsis, Dendrobium and Oncidium. All of them belong to this subfamily. Phalaenopsis or the Moth Orchid is known to bloom around the year. Dendrobium is popular for having the biggest leaves among orchids. The Oncidium or the Dancing Lady is a popular ornamental orchid that has a brilliant sprouting of flowers.

5. Subfamily Vanilloideae

  • A prehistoric and controversial subfamily
  • Earlier regarded as a part of both, Epidendroideae and Orchidoideae