Leptotes (abbreviated Lpt in the horticultural trade) is a small genus of epiphytic orchids in the family Orchidaceae, order Asparagales. It comprises approximately nine species, all native to the Atlantic Forest and adjacent dry forests of south and southeast Brazil, with L. unicolor also occurring in Argentina and L. bicolor extending into Paraguay.
Plants in this genus are characteristically small and caespitose, growing from a short cylindrical rhizome that bears compact pseudobulbs. Each pseudobulb carries one — occasionally two — terete, fleshy leaves that may be erect or pendent, dark green or purple, and often have a wrinkled surface. The inflorescence is apical, generally short, and produces up to seven flowers directly from the apex of the pseudobulb, though fewer flowers per inflorescence is typical.
Leptotes flowers are relatively large in proportion to the plant and are strongly fragrant, with the scent persisting for ten to twenty days. Petals and sepals are elongated and similar in appearance, coloured white, greenish, or various shades of pink. The trilobed labellum — spotted in pale yellow, lilac, or light purple — is distinctive, as is the pollinarium: six pollinia of differing sizes (two large central ones and four smaller lateral ones held by a short caudicle), an arrangement unique among orchids. The rounded, succulent fruits emit a vanilla-like fragrance.
The genus is closely related to Loefgrenianthus and, more distantly, to Pseudolaelia and former Schomburgkia (now partly subsumed into Laelia). The type species, Leptotes bicolor, was described by John Lindley in 1833 from a plant collected in the Serra dos Órgãos mountains of Brazil. Five of the nine currently recognised species were described after 2000, reflecting ongoing botanical exploration of Brazil's Atlantic Forest.
Several species are cultivated by orchid enthusiasts for their showy blooms, though most are considered challenging to grow. Leptotes bicolor in particular has a long record of use as a vanilla substitute — its flowers and fruits flavour milk, ice cream, tea, and confectionery.
Etymology
The name Leptotes was coined by the British botanist John Lindley in 1833, derived from the Greek λεπτότητα (leptotita), meaning "mild" or "delicate," in reference to the delicate appearance of the flowers. The first species described, Leptotes bicolor, was named for its two-coloured flowers — white petals and sepals contrasting with a purple lip.
Distribution
Leptotes species are native to south and southeast Brazil, where the genus reaches its greatest diversity; the states of southeastern Brazil host the highest number of species and densest populations. The range extends from the Serra da Jibóia mountain chain in Bahia state southward to northern Rio Grande do Sul. Two species reach beyond Brazil: L. unicolor grows in Argentina (optimally above 700 m altitude, often on Araucaria and Podocarpus trees), and L. bicolor occurs in Paraguay. Three species show a high degree of endemism in southern Bahia state.
Ecology
All Leptotes species grow epiphytically, typically in the Atlantic Forest; L. vellozicola is notably found on Vellozia shrubs in the drier Chapada Diamantina. Species with wide-open flowers (L. tenuis, L. pauloensis) favour montane cloud forests, while L. bicolor tolerates both cloud forests and the drier plateau woodlands of the Serra do Mar. The pollinator of Leptotes has not been directly observed; based on flower colour and morphology, bees and hummingbirds are both proposed as primary agents.
Cultivation
Leptotes are cultivated as epiphytes and grow best when mounted on plaques of vegetable fibre or tree cork, as their roots rot readily under excessive humidity. Watering and fertilising should be increased during active growth and reduced during dormancy. Plants thrive at intermediate temperatures with filtered sunlight. While some species (L. bicolor, L. unicolor) are relatively widely grown, others are rarely cultivated and remain nearly unknown outside specialist collections.
Taxonomy Notes
Leptotes was established by John Lindley in 1833 based on material flowered in England by orchid collector Mrs. Arnold Harrison. Lindley distinguished the new genus from the then-similar Tetramicra (by pollinarium structure and smaller lateral lip lobes) and from Brassavola (by pollinia count and trilobed lip). A related species, Leptotes blanche-amesiae, with a pouched lip and flat leaves, was later segregated into the monotypic genus Loefgrenianthus by Frederico Hoehne, who also described L. pauloensis in 1934. Phylogenetic study by Cássio van den Berg et al. places Leptotes sister to Loefgrenianthus, together positioned between Pseudolaelia and the Schomburgkia/Laelia clade. As of 2004 four species were considered well established; a burst of descriptions between 2004 and 2006 brought the total to nine.
