Hoya (plant)

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Hoya
Hoyabella 092005.jpg
Hoya lanceolata ssp. bella
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Gentianales
Family: Apocynaceae
Subfamily: Asclepiadoideae
Tribe: Marsdenieae
Genus: Hoya
R.Br. (1810)
Species

See text

Synonyms [1]
  • AbsolmsiaKuntze (1891), nom. superfl.
  • AcanthostemmaBlume (1849)
  • AnatropanthusSchltr. (1908)
  • Antiostelma(Tsiang & P.T.Li) P.T.Li (1992)
  • AstrostemmaBenth. (1880)
  • CathetostemmaBlume (1849)
  • CentrostemmaDecne. (1838)
  • ClemensiaSchltr. (1915), nom. illeg.
  • ClemensiellaSchltr. (1915)
  • CodonanthusHassk. (1842)
  • CyrtocerasBenn. (1838)
  • CystidianthusHassk. (1843)
  • Eriostemma(Schltr.) Kloppenb. & Gilding (2001)
  • HiepiaV.T.Pham & Aver. (2011)
  • MadangiaP.I.Forst., Liddle & I.M.Liddle (1997)
  • MicholitziaN.E.Br. (1909)
  • OtostemmaBlume (1849)
  • PhysostelmaWight (1834)
  • PlocostemmaBlume (1849)
  • PterostelmaWight (1834)
  • ScholliaJ.Jacq. (1811)
  • SperlingiaVahl (1810)
  • TriacmaHasselt ex Miq. (1857)
  • TriplospermaG.Don (1837)

Hoya is a genus of over 500 accepted species of tropical plants in the dogbane family, Apocynaceae. Most are native to several countries of Asia such as the Philippines, India, Thailand, Malaysia, Vietnam, Bangladesh, Indonesia, Polynesia, New Guinea, and many species are also found in Australia.

Contents

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. [2]

Description

Hoya carnosa Hoya carnosa - flower view 01.jpg
Hoya carnosa

Hoyas are evergreen perennial creepers or vines or rarely, shrubs. They often grow epiphytically on trees; some grow terrestrially, or occasionally in rocky areas. They climb by twining, and with the employment of adventitious roots. Larger species grow 1–18 m (3–59 ft), or more, with suitable support in trees. They have simple entire leaves, arranged in an opposite pattern, that are typically succulent. Leaves may exhibit a variety of forms, and may be smooth, felted or hairy; venation may be prominent or not, and many species have leaf surfaces flecked with irregular small silvery spots.

The flowers appear in axillary umbellate clusters at the tip of peduncles. Hoya peduncles are commonly referred to as spurs. In most species these spurs are perennial and are rarely shed. Each flowering cycle increases the length of the spur, and in the larger species can eventually reach 27 cm (11 in) or more. Flowers vary in size from 3 mm (18 in) (Hoya bilobata Schltr.) to over 95 mm (3+34 in) (in H. lauterbachii K. Schuman) in diameter. Flower form is typically star-shaped, with five thick, waxy, triangular petals, topped with another star-shaped structure, the corona. Colours on most species range from white to pink; there are species that exhibit yellow to orange, dark reds to near-black, and there are green flowers. Many are sweetly scented. and most produce abundant nectar.

Pollinators include moths, flies, and ants. Pollination is poorly understood, but plants left outdoors in temperate regions do sometimes produce seed, indicating pollination by local insects.

Seeds are borne in twin pods, actually follicles, are generally light, and are dispersed by the wind by means of a small tuft of silky fluff. Germination is rapid, but viability is not long.

At least some species exhibit Crassulacean Acid Metabolism (CAM), including H. carnosa .

Several species exhibit adaptations for mutualism with ants by providing modified leaves for domatia ("homes"), much as in the related genus Dischidia ; H. imbricata has leaves that form a concave cup over the tree trunk it climbs up to shelter ants, and H. darwinii has arrangements of bullate leaves on its stems to form shelters.

Leaves

Hoya leaves vary in size, texture, colour and venation. In size, leaves range from as small as 5 mm in length and 2 to 4 mm in width (Hoya engleriana Hosseus) to as large as 25 cm by 35 cm. (Hoya latifolia G. Don). Hoya coriacea Blume, has been reported to have leaves as long as two feet in length. 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.). One popular species, Hoya shepherdii Short ex Hook. has leaves that resemble string beans hanging in bunches from their stalks. Hoya linearis Wall. ex D. Don is covered with fine downy hair and resembles masses of Spanish Moss ( Tillandsia usneoides ) hanging from trees in its native habitat. 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 as in H. cinnomomifolia. Some have leaves that are mottled with speckles of silvery white ( Hoya carnosa R. Br., Hoya pubicalyx ). 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 ssp. rupicola, oramicola and saniae from Australia and Hoya pachyclada from Thailand). One of the most succulent, Hoya kerrii Craib, has obcordate (inverse heart-shaped) leaves, with the cleft away from the stem.

Flowers

Hoya mindorensis Hoya mindorensis.jpg
Hoya mindorensis

Hoya flowers are all shaped like five pointed stars. Some species' petals reflex so far that the flowers appear to be round or ball-like. They grow in umbels, or in some species singly (e.g. Hoya Retusa). Umbels can reach impressive proportions in some species, and many species have individual flowers well over 75 mm (3 in) in diameter (H. imperialis Lindl., H. lauterbachii K. Schuman). H. coriacea Blume has been known to have as many as 70 in an inflorescence, each individual measuring nearly 2 cm in diameter with the umbels over 30 cm in breadth. The single-flowered Hoya pauciflora Wight makes up for its paucity by its flower size of nearly 40 mm (1+12 in) in diameter produced at any time of year. Textures of flower surfaces may be glabrous and shiny, to matte, to finely haired, and some being quite hairy. One of the two clones of Hoya mindorensis Schltr., from the Philippines, comes very close to being a true red. Blue, purples, and violets do not appear to be represented in the genus Hoya. Many varieties of Hoya flowers are fragrant, with various notes such as vanilla, citrus, chocolate, and cinnamon. In some cases the scent can be more noticeable in the morning or evening.

Selected species

Species listed here are given in Albers & Meve (2002) and accepted by both The Plant List and Tropicos.

Cultivation and uses

Many species of Hoya are popular houseplants in temperate areas (especially H. carnosa ), grown for their attractive foliage and strongly scented flowers. Numerous cultivars have been selected for different leaf forms or flower colours. Hoyas grow well indoors, preferring bright light, but will tolerate fairly low light levels, although they may not flower without bright light. Hoyas commonly sold in nurseries as houseplants include cultivars of H. carnosa (Krimson Queen, Hindu Rope − compacta), H. pubicalyx (often mislabelled as H. carnosa or H. purpurea-fusca), and H. kerrii . Hoyas are easy to propagate, and are commonly sold as cuttings, either rooted or unrooted, or as a potted plant.

Hoya carnosa has been shown in recent studies at the University of Georgia to be an excellent remover of pollutants in the indoor environment. [3]

Various cultures have used hoyas medicinally, especially Polynesian cultures.[ citation needed ] Some are toxic to livestock and sheep poisonings in Australia are reported.[ citation needed ]

Several Hoya species and cultivars are excellent terrarium plants.[ citation needed ]

Rachel Colette Conroy was appointed the International Cultivar Registration Authority for Hoya in 2023. [4]

Related Research Articles

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<i>Alstonia</i> Genus of flowering plants

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<i>Hoya carnosa</i> Species of plant

Hoya carnosa, the porcelainflower or wax plant, is a species of flowering plant in the dogbane family Apocynaceae. It is one of the many species of Hoya that are native to Eastern Asia and Australia. It is a common house plant grown for its attractive waxy foliage, and sweetly scented flowers. It is grown well in pots and hanging baskets.

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<i>Adenium obesum</i> Species of plant

Adenium obesum, more commonly known as a desert rose, is a poisonous species of flowering plant belonging to the tribe Nerieae of the subfamily Apocynoideae of the dogbane family, Apocynaceae. It is native to the Sahel regions south of the Sahara, tropical and subtropical eastern and southern Africa and also the Arabian Peninsula. Other names for the flower include Sabi star, kudu, mock azalea, and impala lily. Adenium obesum is a popular houseplant and bonsai in temperate regions.

<i>Zoysia matrella</i> Species of plant

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Dischidia is a genus of plants in the “dog-bane” family Apocynaceae, collectively known as the “milkweeds”. They are epiphytes, native to tropical areas of China, India as well as Bhutan’s southern borders, wherever minimal frost occurs. Additionally, they are known from most areas of Mainland Southeast Asia, including forested areas of Myanmar, Thailand, Vietnam, Cambodia, Laos, and some parts of Indonesia, Malaysia and Singapore. Several species are also native to Papua New Guinea and northeastern Australia.

<i>Hoya meliflua</i> Species of plant in the family Apocynaceae

Hoya meliflua is a species of vine in the Apocynaceae family. It is endemic to the Philippines. The vine is common to Apayao, La Union, Rizal, Bataan, Laguna, Mindoro, Palawan, Negros, Panay, and Leyte.

<i>Thelasis</i> Genus of orchids

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<i>Hoya aldrichii</i> Species of plant

Hoya aldrichii, commonly known as the Christmas Island waxvine, is a species of flowering plant in the Apocynaceae or dogbane family. It is a vine that is endemic to Christmas Island, an Australian territory in the north-eastern Indian Ocean, where it is a common epiphyte in the shrublands of the island's coastal terraces. The specific epithet honours Captain Aldrich, commander of the survey vessel HMS Egeria, which visited Christmas Island in 1887.

<i>Hoya kerrii</i> Species of plant

Hoya kerrii, also referred to colloquially as Hoya hearts, is a species of Hoya native to the south-east of Asia. Its eponymous collector is Arthur Francis George Kerr, Irish physician and botanist.

<i>Persoonia coriacea</i> Species of flowering plant

Persoonia coriacea, commonly known as the leathery-leaf persoonia, is a species of flowering plant in the family Proteaceae and is endemic to the south-west of Western Australia. It is an erect to spreading shrub with smooth bark, spatula-shaped or elliptic to linear leaves and bright yellow flowers borne in groups of up to ten along a rachis up to 70 mm (2.8 in) long.

<i>Hoya bilobata</i> Species of plant

Hoya bilobata, commonly known as wax plant or porcelain flower, is a smaller species of the genus Hoya native to the Philippines. Hoya bilobata is just one of over 200 species of the genus Hoya.

<i>Hoya bella</i> Species of flowering plant

Hoya bella, the beautiful hoya, waxflower or pretty waxflower, is a species of tropical epiphyte with trailing stems, slightly succulent leaves and pendant umbels of fragrant, white and purple flowers. It is an asclepiad in the periwinkle and milkweed family, Apocynaceae.

<i>Hoya pubicalyx</i> Species of plant

Hoya pubicalyx is a species of flowering plant in the genus Hoya native to the Philippines. Sometimes confused for Hoya carnosa, it has succulent, lanceolate foliage and grows in a vining habit epiphytically. Kept as a houseplant in temperate climates, it can be found in variegated forms in nurseries. The Philippine five-centavo coin of the New Generation Currency Series features the flowers of this plant.

References

  1. Hoya R.Br. Plants of the World Online . Retrieved 27 July 2023.
  2. Robert Brown (1810). Prodromus florae Novae Hollandiae et Insulae Van-Diemen, exhibens characteres plantarum quas annis 1802-1805 per oras utriusque insulae collegit et descripsit Robertus Brown; insertis passim aliis speciebus auctori hucusque cognitis, seu evulgatis, seu ineditis, praaesertim Banksianis, in primo itinere navarchi Cook detectis. Vol. 1. London: Richard Taylor and Biodiversity Heritage Library. p. 459.
  3. University of Georgia (31 March 2009). UGA research shows some plants can remove indoor pollutants.
  4. "ICRA Report Sheet". International Society for Horticultural Science. Retrieved 12 October 2023.

Bibliography