Hoya (plant)

For other uses, see Hoya (disambiguation) or Georgetown Hoyas.

Hoya
Hoya bella
Scientific classification
Kingdom:	Plantae
Division:	Magnoliophyta
Class:	Magnoliopsida
Order:	Gentianales
Family:	Apocynaceae
Subfamily:	Asclepiadoideae
Genus:	Hoya R.Br.
Species
See text.

Hoya is a genus of 200-230 species of tropical climbing plants in the family Apocynaceae, native to southern Asia (India east to southern China and southward), Australia, and Polynesia. Common names for this genus are waxplant, waxvine, waxflower or simply hoya. This genus was named by botanist Robert Brown, in honour of his friend, botanist Thomas Hoy.

Hoyas are evergreen climbing vines or shrubs growing to 1-10 m (or more with suitable support in trees). They have simple opposite leaves 5-30 cm long that are typically succulent, and in many species are flecked with irregular small silvery spots.

The flowers appear in axillary umbellate clusters at the apex of 2-3 cm peduncles, with repeated clusters of flowers developing sequentially on each peduncle. The flowering peduncles get 2-3 mm longer with each flowering, and can eventually reach 7 cm or more long; the base of the peduncle is smooth, with growth subsequent to the first flowering of the peduncle is rough with numerous tiny bracts. Each flower is about 1 cm diameter, with five thick, waxy, triangular petals; colours range from white to pink or yellow. They are sweetly scented and produce abundant nectar.

Cultivation and uses

Many species are popular houseplants in temperate areas (especially H. carnosa), grown for their attractive foliage and strongly scented flowers. Numerous cultivars have been selected for garden use.

• 
  Hoya carnosa
  as a houseplant
• 
  Hoya carnosa
  Inflorescence peduncle, several years old
• 
  Hoya carnosa
  Inflorescence
• 
  Hoya carnosa
  Single flower

Leaves

Hoya leaves vary in size, texture, colour and venation. In size they range from a centimetre in length and from two to four millimetres in width (Hoya engleriana, Hosseus) to 25 cm. by 25 cm. (Hoya latifolia, G. Don). Hoya coriacea, Blume, is said to sometimes have leaves as long as two feet in length. One of the most succulent of the lot, Hoya kerrii, Craib, has perfect valentine shaped leaves, with the notches at the apexes of the leaves instead of at the bases. This species has two forms, one with glabrous leaves and one with suede textured leaves. There are hoyas with almost perfectly round leaves and others with linear leaves (Hoya linearis, Wall. ex. D. Don and Hoya teretifolia, Griff. ex Hook. f.). A popular species, Hoya shepherdii, Short ex Hook. has leaves that look for the world like bunches of string beans hanging from their stalks. Hoya linearis, Wall. ex D. Don is covered with fine downy hair and greatly resembles masses of Spanish Moss (Tillandsia useneoides) hanging from trees in its native habitat. Some Hoya leaves are smooth and shiny; some are covered with hairs. Some Hoya leaves appear to be veinless while others have very conspicuous veins of a lighter or darker colour than the rest of the leaves. Some have leaves that are mottled with speckles of silvery white (Hoya carnosa, R. Br.). Some Hoya leaves are smooth and shiny and others are covered with hairs. Some hoyas have leaves that are thin and translucent (Hoya coriacea, Blume); some are so thick and succulent that they look more like crassulas than hoyas (Hoya australis subsp. rupicola, oramicola and saniae from Austrailia and Hoya pachyclada from Thailand).

Flowers

Hoya flowers are just as varied as the leaves, despite the fact that all are shaped like five pointed stars. They grow in umbels, usually with many flowers per umbel. Individual flowers range in size from as small as four to five millimetres in diameter (Hoya bilobata, Schltr.) to well over three inches in diameter (Hoya imperialis, Lindl. and H. macgillivrayi, F. M. Bailey). The number of flowers per umbel varies from one (H. pauciflora, Wight.) to 55 or even more. Hoya coriacea, Blume has been known to have as many as 70, each measuring nearly 2 centimetres in diameter. The single flowered Hoya pauciflora, Wight makes up for its paucity by its flower size of nearly an inch and a half in diameter.

Just as hoyas vary in size, they also vary in texture, some being glabrous and shiny and some being quite hairy. They also vary in colour. They come in the purest white, varying shades of pink from almost white to rubber-doll or bubble-gum pink, yellowish-pink, yellow, green, purple, brownish-red and brown. There are some that are so dark that they are often referred to as black. Until recently it was thought that a true red hoya was not ever likely to appear but recent discoveries make that seem possible. One of the two clones of Hoya mindorensis, Schltr., from the Philippines, which are currently in circulation, comes very close to being a true red. Blue still does not appear to be represented in the Hoya genus.

Selected species

Hoya acuta Hoya affinis Hoya albiflora Hoya aldrichii Hoya anulata Hoya arnottiana Hoya australis - Australian Waxflower Hoya archboldiana Hoya bella - Beautiful Hoya Hoya benquetensis Hoya bhutanica Hoya bilobata Hoya bordenii Hoya brevialata Hoya burtoniae Hoya callistophylla Hoya calycina Hoya campanulata Hoya camphorifolia Hoya carnosa - Porcelain Flower, Waxplant Hoya caudata Hoya cembra Hoya chlorantha Hoya chuniana Hoya ciliata - Black Hoya Hoya cinnamomifolia Hoya citrina Hoya clemensiorum Hoya collina Hoya cominsii Hoya compacta Hoya coriacea Hoya coronaria Hoya cumingiana Hoya curtisii Hoya darwinii Hoya davidcummingii Hoya dennisii Hoya densifolia Hoya deykei Hoya dimorpha Hoya diptera Hoya dischorensis Hoya diversifolia Hoya dolicosparte Hoya elliptica Hoya endauensis Hoya engleriana Hoya erythrina Hoya erythrostemma Hoya eitapensis Hoya excavata Hoya flagelleta Hoya flavescens

Hoya flavida Hoya fraterna Hoya fungii Hoya glabra Hoya globulosa Hoya gracilis Hoya greenii Hoya grifithii Hoya guppyi Hoya halophila Hoya heuschkeliana Hoya hypolasia Hoya kanyakumariana Hoya kenejiana Hoya kentiana Hoya kerrii - Valentine Hoya Hoya imbricata (Hoya pseudomaxima) Hoya imperialis - Honey-plant Hoya inconspicua Hoya incrassata Hoya incurvula Hoya ischnopus Hoya juanngoiana Hoya lacunosa Hoya lambii Hoya lasiantha Hoya latifolia Hoya lauterbachii Hoya limoniaca Hoya linearis Hoya litoralis Hoya lobbii Hoya loheri Hoya longifolia Hoya macgillivrayi Hoya macrophylla Hoya magnifica Hoya megalaster Hoya meliflua Hoya merrillii Hoya micrantha Hoya microphylla Hoya mindorensis Hoya mitrata Hoya montana Hoya motoskei - Spotted Waxplant Hoya multiflora - Shooting Star Hoya Hoya naumanii Hoya nawbawenensis Hoya neocaldonica Hoya neo-ebudica Hoya noid Hoya nummularioides Hoya obovata

Hoya obscura Hoya obtusifolioides Hoya odetteae Hoya onychoides Hoya oreogena Hoya pachyclada Hoya padangensis Hoya palawanica Hoya pallilimba Hoya parasitica Hoya parviflora Hoya patella Hoya pauciflora Hoya pentaphlebia Hoya picta Hoya pimenteliana Hoya plicata Hoya polystachya Hoya polyneura - Fishtail Hoya Hoya pottsii Hoya pubicalyx Hoya pulchella Hoya purpurea Hoya purpureo-fusca Hoya pusilla Hoya retusa Hoya revoluta Hoya ridleyi Hoya rigida Hoya ruscifolia Hoya samoensis Hoya schneei Hoya serpens Hoya shepherdii - String Bean Hoya Hoya siariae Hoya sigillatis Hoya sipitangensis Hoya solaniflora Hoya subcalva Hoya subglabra Hoya subquintuplinervis Hoya teretifolia Hoya thailandica Hoya thomsonii Hoya verticillata Hoya vitellinoides Hoya vitiensis Hoya wallichii Hoya walliniana Hoya wayetii Hoya waymaniae Hoya wightii Hoya wilbergiae