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In addition to Vanilla fragrans, there are two other species of the genus Vanilla, out of the 50 species, which are occasionally cultivated, though they yield an inferior product. They are listed below.
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Vanilla pornpona Schiede, known as West Indian vanilla, which occurs wild in Mexico, Central America and Trinidad and is cultivated to a small extent in Guadeloupe. It resembles V fragrans, but the leaves are larger. The flowers are also larger and more fleshy. The cylindrical pods are shorter and thicker.
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V tahitensis (Tahitian vanilla) is indigenous to Tahiti and is cultivated there and also in Hawaii. It is less robust than V fragrans with more slender stems and narrower leaves. The pods taper towards each end.
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V fragrans is a fleshy, herbaceous perennial vine, climbing by means of adventitious roots up onto trees or other supports to a height of 10-15 m, but in cultivation it is trained to a convenient height to facilitate hand-pollination and harvesting. The adventitious roots are long, whitish, aerial, singly opposite to the leaves and adhere firmly appressed to the support upon which the plant climbs. The long, cylindrical, monopodial stem is simple or branched, succulent, flexuose, brittle and has internodes that are 5-15 cm long. They are dark green and bear photosynthethic leaves with stomata. The leaves are large, 8-25 cm long and 2-8 cm broad, flat, fleshy, subsessile and alternate, oblong-elliptic to lanceolate. The tip is acute to acuminate and the base is somewhat rounded. The petiole is short, thick and canalised above.
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The protruding inflorescences are axillary, racemose, usually simple, and only rarely branched, borne towards the top of the vine, with up to 20-30 flowers, opening from the base upwards, generally with only 1-3 flowers opening at one time and each lasting one day. The bracts are rigid, concave and persistent.
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The flowers are large, waxy, fragrant and a pale-greenish yellow. The pedicil is very short and the ovary is inferior, cylindrical, tricarpellary. There are three sepals, which are obtuse to sub-acute and slightly reflexed at the opening. The two upper petals resemble the sepals in shape, but are smaller. The lower petal is modified as a trumpet-shaped labellum or lip, which is shorter than the other perianth lobes. Darker-coloured papillae form a crest in the median line, with a tuft of hair in the middle of the disc. The column or gynostemium is attached to the labellum. It is hairy on the inner surface, bearing at its tip the single stamen containing the two pollen masses or pollinia covered by a cap, and below is the concave sticky stigma, which is separated from the stamen by the thin flap-like rostellum.
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The fruit is a capsule, known in the trade as a bean, is pendulous, narrowly cylindrical, obscurely three-angled, 10-20 cm long and 1.5 and 4.5 cm in girth. It is aromatic on drying, containing when ripe, myriads of very minute globose seeds. In commercial production, the capsules are harvested before they are quite ripe.
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