| Alstonia | |
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| Alstonia scholaris, habit (above), details (below) | |
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Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Asterids |
| Order: | Gentianales |
| Family: | Apocynaceae |
| Subfamily: | Rauvolfioideae |
| Tribe: | Alstonieae |
| Genus: | Alstonia R.Br.[1] |
| Type species | |
| Alstonia scholaristyp. cons. R.Br.[2] | |
| Synonyms[1] | |
Alstonia is a widespreadgenus ofevergreen trees and shrubs, of the familyApocynaceae. It was named byRobert Brown in 1811, afterCharles Alston (1685–1760), professor of botany atEdinburgh from 1716 to 1760.
The type speciesAlstonia scholaris (L.) R.Br. was originally namedEchites scholaris byLinnaeus in 1767.
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Alstonia consists of about 40–60species (according to different authors) native to tropical and subtropical Africa, Central America, Southeast Asia, Polynesia and Australia, with most species in theMalesian region.[1]
These trees can grow very large, such asAlstonia pneumatophora, recorded with a height of 60 m and a diameter of more than 2 m.[3]Alstonia longifolia is the only species growing in Central America (mainly shrubs, but also trees 20 m high).[4]
The leathery, sessile, simple leaves are elliptical, ovate, linear or lanceolate and wedge-shaped at the base. The leaf blade is dorsiventral, medium-sized to large and disposed oppositely or in a whorl and with entire margin. The leaf venation is pinnate, with numerous veins ending in a marginal vein.Phyllotaxy iswhorled i.e. two or more leaves arises at a node and form a whorl .
Theinflorescence is terminal or axillary, consisting of thyrsiformcymes or compoundumbels. The small, more or less fragrant flowers are white, yellow, pink or green and funnel-shaped, growing on a pedicel and subtended bybracts. They consist of 5 petals and 5sepals, arranged in four whorls. The fertile flowers are hermaphrodite. The gamosepalous green sepals consist of ovate lobes, and are distributed in one whorl. The annular disk is hypogynous. The five gamesepalous petals have oblong or ovate lobes and are disposed in one whorl. Thecorolla lobes overlapping to the left (such asA. rostrata) or to the right (such asA. macrophylla) in the bud. Theovary has 2 separate follicles with glabrous or ciliate, oblong seeds that develop into deep blue podlike, schizocarpfruit, between 7–40 cm long. The plants contain a milky latex, rich in poisonousalkaloids. Fijians use the latex ofA. costata (saurua,sorua) as a form of chewing gum.[5] TheAlstonia macrophylla is commonly known in Sri Lanka as 'Havari nuga' or the 'wig banyan' because of its distinct flower that looks like a woman's long wig.
Alstonia trees are used in traditional medicine.[6]
ManyAlstonia species are harvested for timber, calledpule orpulai in Indonesia and Malaysia. Trees from the sectionAlstonia produce lightweight timber, while those from the sectionsMonuraspermum andDissuraspermum produce heavy timber.
Alstonia trees are widespread and mostly not endangered. However a few species are very rare, such asA. annamensis,A. beatricis,A. breviloba,A. stenophylla andA. guangxiensis.
Alstonia has five distinct sections, each amonophyletic group;Alstonia,Blaberopus,Tonduzia,Monuraspermum,Dissuraspermum.[citation needed]
As of April 2025[update],Plants of the World Online accepts the following 44 species:[1]
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