Family : Apocynaceae
Text © Pietro Puccio
English translation by Mario Beltramini
The species is native to the Philippines (Luzon) where it grows on the trees of the humid forests, often along the banks of the water streams.
The genus is dedicated to Thomas Hoy (ca. 1750-1822), botanist and curator of the gardens of the Duke of Northumberland; the name of the species is the combination of the Latin substantive “pubes, eris” = fluff and of the Greek substantive “κάλυξ” = calyx, with reference to the outer surface of the calyx, slightly pubescent.
The Hoya pubicalyx Merr. (1918) is an evergreen climbing epiphyte with stems, that can reach some metres of length, provided of adventitious roots with which they anchor to the supports. The leaves, on an about 1 cm long petiole, are simple, opposite, oblong-obovate to oblong with acuminate apex and entire margin, fleshy, 8-15 cm long and 3-5 cm broad, of glossy intense green colour with grey-silvery spots. Umbel axillar inflorescences, of 7-9 cm of diameter, carrying up to more than 30 flowers of 1,5-1,8 cm of diameter, perfumed, lasting about two weeks; the peduncle is remontant therefore it is not to be cut after the blooming. Slightly pubescent calyx externally, corolla of intense pink to dark purple red colour, thickly covered by white papillae that grant it a velvety look, with 5 almost triangular lobes with acuminate and curved apex, and crown with ovate-lanceolate lobes with acuminate apex, about 0,5 cm long. The fruits are fusiform follicles containing numerous seeds provided at one extremity of a tuft of silky hairs that favour their dispersion with the wind. They have selected several cultivars that differ for the colour of the flowers and of the lreaves.It usually reproduces by cutting, with 2-3 nodes, in very sandy loam or agriperlite maintained humid at a temperature of 26-28 °C, and by air layering; less frequently by seed, in late spring, placed superficially on organic loam wit addition of siliceous sand or agriperlite maintained constantly humid, but without stagnations.
It is a species discussed on the point of view of the nomenclature, as there is no agreement between the scholars if to consider it as a species or as a synonym. Vigorous, floriferous and of easy cultivation, it is utilizable in open air in the tropical, subtropical and marginally temperate-warm climate zones in very luminous position, from filtered sun light to slight shade. Elsewhere, it can be cultivated in pot as climber on appropriate supports, or as drooping in suspended pots, to be sheltered in winter in particularly luminous location, even with some hours of sun in the morning in winter, with lowest temperatures over the 15 °C, even if it can stand some degree less without damage. It is a plant sensitive to the displacements that may originate the premature fall of the flowers even if in bud. It requires a very aerated and draining substratum, rich of organic substance, neutral or slightly acidic, and regular and abundant waterings in summer, but allowing the substratum to dry up completely before giving water again, almost suspended in winter, during the vegetative rest, but without making the leaves shrivel; useful are in summer the nebulizations with non calcareous water at ambient temperature in presence of dry air and high temperatures. For the fertilizations may be used the same products as for the epiphytic orchids. The repottings are to be done when the substratum gives signs of deterioration, preferably between spring and early summer, paying attention to leave the plant dry for various days, until when signs of vegetative regrowth do appear.