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The Epidendroideae, or epidendroid orchids, are a subfamily of the orchid family (Orchidaceae).
The former subfamily Vandoideae has become a specialised clade within a more broadly defined Epidendroideae
This is the largest subfamily, larger than all the other orchid subfamilies together. It comprises more than 15,000 species in 576 genera.
Most are tropical epiphytes (usually with pseudobulbs), but some are terrestrials and even a few saprophytes. Several genera live in a symbiotic relationship with micorrhyza, with the fungi supplying the plant with water and nutrients and receiving in exchange carbohydrates.
They typically contain the remaining orchids with a single, fertile anther ( = monandrous), which is also fully incumbent(= strongly convex) to suberect (= ascending towards the edges). The anther form arises from column elongation or, as in the vandoids, from early anther bending. The incumbent anther forms a right angle with the column axis or is pointed backward in many genera.
Most have hard pollinia, i.e. a mass of waxy pollen or of coherent pollen grains. The pollinia are with caudicle and viscidium or without.
The stigma are entire or 3-lobed; a beak is present. The apical part of the muiddle stigma lobe forms a stipe ( = pollinium stalk).
The ovary is 1-locular.
The leaves are distichous or spiraling, growing on thickened stems.
The Epidendroideae are difficult to classify. They have been divided in lower epidendroids and higher epidendroids
The lower epidendroids are paraphyletic and contain the following tribes :
- Sobralliinae
- Neottieae
- Palmorchideae
- Tropidieae
- Diceratostelae
- Triphoreae
- Nervilieae
- Gastrodieae (achlorophyllous)
- and the anomalous genus Xerorchis
The higher epidendroids are partly monophyletic and partly polyphyletic (tribes Arethuseae and Epidendreae).
- Maxillarieae
- Cymbidieae
- Vandeae
- Epidendreae II
- Calypsoeae (problematic, difficult to classify)
- Dendrobieae
- Malaxideae
- Podochileae
- Epidendreae I
- Arethuseae
- Coelogyneae
This classification has a rather ephemeral nature. Changes are likely to occur as new data become known.
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