Stelis, commonly known as leach orchids, is a large genus of flowering plants in the family Orchidaceae (order Asparagales), comprising around 1,339 accepted species. The genus is one of the most species-rich within the subtribe Pleurothallidinae and is closely allied to Pleurothallis and Masdevallia. Several formerly segregate genera — Apatostelis, Dialissa, Humboldtia, and Steliopsis — are now generally subsumed within Stelis, and cladistic research by Pridgeon, Solano, and Chase has confirmed the genus is monophyletic.
Plants are predominantly epiphytic, growing on the bark of trees in humid forest habitats, and only rarely lithophytic. The vegetative structure is slender: a single oblanceolate leaf emerges from narrow, leathery outgrowths along a creeping stem. Inflorescences are long, dense racemes bearing small to minute flowers in diverse shades of white; other colours are unusual. The flowers are notably photosensitive, opening in sunlight and in many species closing completely at night. The floral architecture is distinctive: three symmetrically rounded sepals form a triangle enclosing a compact central structure composed of the column, diminutive petals, and a small lip.
Stelis ranges across much of tropical and subtropical America — South America, Central America, Mexico, the West Indies, and as far north as Florida. Although the genus is exceptionally diverse in the wild, it is not commonly encountered in cultivation.
The genus was first documented by French botanist Charles Plumier during an expedition to the Antilles commissioned by Louis XIV around 1690, and a herbarium specimen is thought to represent the first American orchid brought to Europe, depicted in Tabernaemontanus' herbal of 1591. The genus was formally named Stelis in 1799 by Swedish botanist Olof Swartz, replacing the preoccupied name Humboltia that Ruiz and Pavon had earlier applied. In the horticultural trade the genus is abbreviated Ste.
Etymology
The name Stelis derives from the ancient Greek word for "mistletoe," an allusion to the epiphytic lifestyle shared by most species in the genus, which grow anchored to the bark of host trees rather than in soil.
Distribution
Stelis is widely distributed throughout tropical and subtropical America, with the greatest diversity in South America. The range extends through Central America and Mexico, across the West Indies, and reaches its northern limit in Florida. Species grow predominantly as epiphytes in humid montane and lowland forests.
Taxonomy Notes
Stelis belongs to the family Orchidaceae (order Asparagales) and sits within the subtribe Pleurothallidinae, closely related to Pleurothallis and Masdevallia. Cladistic analysis (Pridgeon, Solano & Chase) confirmed the genus as monophyletic, though its boundaries with several Pleurothallis subgenera remain blurred. The genera Apatostelis Garay, Dialissa Lindl., Humboldtia Ruiz & Pav., and Steliopsis Brieger are generally included within Stelis. The genus abbreviation in horticultural literature is Ste.
History
Stelis was first documented by Charles Plumier, a French Franciscan friar and botanist dispatched by Louis XIV to survey the flora of the Antilles around 1690; he described collections from Dominica and neighbouring islands in his 1703 Nova Plantarum Americanarum Genera. Subsequent accounts came from Nikolaus von Jacquin, who described the same plant (Epidendrum ophioglossoides) in two Caribbean floristic works of 1760 and 1763. The name Stelis was formally established by Swedish botanist Olof Swartz in 1799, replacing Humboltia — a name coined by Ruiz and Pavon during the Spanish Botanical Expedition to Peru and Chile — after Swartz discovered that name was already occupied. Epidendrum ophioglossoides became the type species of the genus. A herbarium specimen believed to be a Stelis is recorded as the first American orchid depicted in European literature, appearing in Tabernaemontanus' 1591 herbal.
