Vanilla Bean Orchid
Climbing orchids with robust vine-like green stems with large fleshy leaves. Branches on the upper parts of the stems produce racemes or panicles that carry numerous relatively large fragrant flowers. Each flower is short-lived but they are produced in succession from each inflorescence. The flowers, which are up the right way, have incurved to spreading sepals and petals. The labellum is mostly fused to the column margins to form a funnel-shaped chamber. It is ornamented with thickened veins, ridges and hairs. The column lacks a column foot.
Similar Genera
Significant Generic Characters
Robust climbing orchids with long, green, branching, scrambling stems and large green leaves (some species are leafless); inflorescences axillary, racemose, paniculate or cymose; flowers relatively large, fragrant, short-lived, opening in sequence; perianth segments of similar length, free, fleshy, the petals narrower than the lateral sepals; labellum variously attached to the margins of the column, forming a funnel-shaped chamber, rarely free, the ventral surface bearing ridges, keels, thickened veins and clusters of unusual fringed scales; column narrow, apically winged, without a column foot.
Size and Distribution
A genus of about 107 species distributed in tropical America, Africa, Madagascar, South-east Asia, Malaysia, Philippines, Indonesia, New Guinea but not native to Australia. However, a single species, V. planifolia, has become naturalised near Cairns and at Frenchmans Creek near Bellenden Ker in northeastern Queensland. State occurrence: Queensland.
Ecology
Species of Vanilla mainly grow in warm to hot wet tropical forests of the lowlands, although some leafless species occur in tropical deciduous forest. In Australia V. planifolia grows in tropical lowland rainforest, the plants climbing on trees and scrambling over the intervening ground and vegetation. Naturalisation in Australia seems to be from vegetative means rather than from seed.
Biology
Pollination: The flowers of Vanilla planifolia are fragrant and insect-pollinated.
Reproduction: Vanilla planifolia reproduces from seed and by the stems taking root and spreading as separate plants. Apomixis is unknown in the genus.
Seasonal Growth: The stemsof Vanilla planifolia grow regularly throughout the year, particularly in spring and summer (monsoons).
Flowering: Vanilla planifolia flowers sporadically over the summer months. The buds reach a certain stage of development and remain quiescent before opening rapidly following an environmental stimulus. Each flower lasts 1-2 days.
Hybrids: Natural hybridisation involving Vanilla planifolia is unknown.
Fire: Plants of Vanilla planifolia do not grow in fire-prone habitats.
Derivation
The generic name is derived from the Spanish vainilla, little pod, in reference to the bean-like pods of the cultivated Vanilla planifolia.
Botanical Description
Perennial leafless geophytic or epiphytic herbs with climbing stems. Plants glabrous. Roots thin, appressed to the host or aerial, unbranched. Stems monopodial,thick,erect, elongate, climbing, branched, green, smooth or warty, sometimes grooved. Leaves distichous or spirally arranged, sessile or petiolate, membranous to fleshy, sometimes reduced to evanescent bracts. Inflorescence axillary, racemose to paniculate, rarely cymose, multiflowered. Peduncle wiry, about as long as the rhachis or longer, glabrous. Sterile bracts small to large, sometimes foliaceous. Rhachis condensed to elongate, straight or curved. Floral bracts reduced and scale -like. Pedicels long, straight or curved, merging with the ovary. Ovary short, barely indistinguishable from the pedicel, smooth. Flowers resupinate, often not opening widely, the flowers gullet-shaped, pale coloured (greenish or yellowish), short-lived, opening sequentially in a spiral, pedicellate. Perianth segments incurved to spreading, fleshy. Dorsal sepal free, subsimilar to the lateral sepals, smooth, granular or warty. Lateral sepals free, subsimilar to the dorsal sepal, smooth, granular or warty. Petals free, narrower than the sepals, undulate to contorted, often with a dorsal ridge. Labellum variously fused to the column margins, rarely free, forming a saccate or funnel-shaped chamber (pseudospur), dissimilar in size and shape to the sepals and petals, ecalcarate. Labellum lamina stalked at the base, unlobed or 3-lobed; ventral surface glabrous or pubescent, sometimes warty; margins entire or undulate/crispate. Callus consisting of medial ridges or keels, thickened veins and penicillate clusters of fringed scales. Nectar unknown. Spur absent. Column elongate, narrow, straight or curved, terete or trigonous, lacking free filament and style, glabrous or pubescent, sometimes with basal keels. Column foot absent. Pseudospur present (see labellum). Column wings apical. Anther terminal, 2-celled, persistent, versatile, with a short rostrum. Pollinarium absent. Pollinia 2, poorly formed, powdery, sticky, yellow. Pollen grains in monads. Viscidium absent. Rostellum poorly developed, ventral, sometimes sticky. Stigma entire, concave, with thickened margins, sometimes the lobes extended as flaps. Capsules dehiscent, (sometimes a partly dehiscent berry), elongate-cylindric, glabrous, pendulous; pedicels not elongating in fruit; peduncle not elongating in fruit. Seeds numerous, large, sclerotic, wingless, smooth or slightly warty.
Taxonomy
Vanilla is a complex polyphyletic genus that will probably be split into several genera (Soto Arenas 2001).
Notes
Vanilla planifolia is a popular horticultural plant in tropical areas of Queensland where it is often grown as a garden plant.
Nomenclature
Vanilla Plumier ex Miller, Gard. Dict. abridged ed. 4 (4) without page number (1754).
Lectotype species: Epidendrum vanilla L. [Vanilla mexicana Miller], fide Mansf. in Kulturpfl., 2: 587 (1959).
Infrageneric Taxa: Vanilla has been divided into sections but requires reassessment.
References
Soto Arenas, M.A. (2001). Vanilla in Genera Orchidacearum, Vol. 3, Orchidoideae (Part 2), Vanilloideae, Eds. A.M.Pridgeon, P.C.Cribb & M.W.Chase, pp. 321-334.