Clerodendrum is a genus of flowering plants in the mint family, Lamiaceae, comprising roughly 240 to 400 accepted species depending on the authority consulted — published estimates have historically ranged anywhere from 150 to 450 names. The genus was erected by Linnaeus in Species Plantarum (1753) and was for centuries placed in the family Verbenaceae; molecular phylogenetic work in the 1990s moved it into Lamiaceae alongside other former verbenaceous lineages.
Most members of the genus are shrubs or small trees, with a smaller number of herbaceous perennials and woody climbers. Leaves are opposite or whorled, and the showy flowers are borne in cymes or panicles with five nearly equal corolla lobes and four didynamous stamens (two long, two short). The fruit is a drupe — typically obovoid to oblong — partly enclosed within an enlarged, often brightly coloured calyx that persists after the petals drop, a feature that gives many species their ornamental "starburst" appearance in late summer and autumn.
The genus is distributed across the tropical and warm temperate regions of the world, with the greatest diversity in tropical Africa and southern Asia and additional native representatives in the tropical Americas and northern Australasia. Australia hosts nine species (seven endemic), spanning Queensland, New South Wales, the Northern Territory, and Western Australia.
Clerodendrum flowers display an unusual reproductive strategy that combines dichogamy and herkogamy to discourage self-pollination. The flowers are protandrous: when they open, the stamens stand erect and shed pollen while the style is bent down out of the way; once pollen has been released, the stamens curl back and the style straightens up, lifting the stigma into the centre of the flower so it can receive pollen from other plants. Butterflies and hummingbirds are frequent visitors to the nectar-rich blooms.
Several species are widely grown as ornamentals in warm climates, including C. trichotomum (harlequin glorybower), C. thomsoniae (bleeding heart vine), C. bungei (rose glorybower), C. chinense, C. splendens, C. wallichii, and C. speciosissimum. Many bear strongly fragrant flowers. Some species — most notably C. bungei — spread aggressively by root suckers and can become weedy outside their native ranges.
Etymology
The genus name Clerodendrum was coined by Linnaeus from two Greek roots: kleros, meaning "chance" or "fate," and dendron, meaning "tree." The curious "chance" element is generally explained as a reference to the wildly inconsistent reports of the plants' medicinal usefulness that circulated in early botanical literature — Linnaeus's contemporaries could not agree on what these trees were good for. The Asian religious associations of several species, which were planted around shrines and temples, are also cited as motivation for the name.
Distribution
Clerodendrum is pantropical, with native species in tropical Africa, southern Asia, the tropical Americas, and northern Australasia, plus a small temperate extension into eastern Asia. The centres of diversity are tropical Africa and southern Asia. PlantNET reports approximately 400 species across the genus worldwide; more conservative treatments give roughly 240 accepted species. In Australia nine species occur, of which seven are endemic, distributed across Queensland, New South Wales, the Northern Territory, and Western Australia; in New South Wales the native species are C. inerme, C. tomentosum, and C. floribundum.
Ecology
Clerodendrum flowers are notable for a combined dichogamous and herkogamous mechanism that strongly discourages self-pollination. Each flower is protandrous: in the male phase the stamens are held erect and shed pollen onto visiting insects while the style is bent down and the stigma kept clear of the pollen. After pollen release the stamens curl back or droop, and the style straightens upward to place the stigma where the stamens previously stood, so that subsequent visitors transfer cross-pollen onto it. The tubular, often brightly coloured corollas and copious nectar attract butterflies and hummingbirds, which are reported as common pollinators.
Cultivation
Several Clerodendrum species are grown as ornamental shrubs, small trees, or vines for their showy and often fragrant flowers — Missouri Botanical Garden's Plant Finder lists C. bungei, C. splendens, C. thomsoniae, C. trichotomum, and C. wallichii among commonly cultivated taxa. Plants generally prefer full sun and moist, well-drained soil, with shelter from cold drying winds. Hardiness varies by species: C. trichotomum tolerates roughly USDA zones 6–11 and survives to about -10 °C, resprouting from the base after hard winters, while C. bungei is hardier-rooted but commonly behaves as a die-back subshrub in zones 7–9. Growth rate is medium, and most cultivated species mature at around 2 m tall.
Propagation
Typical of several cultivated Clerodendrum species, C. bungei propagates readily from seed but spreads vigorously by underground root suckers, which is also a common practical method for increasing plants in cultivation. The same suckering habit makes the plants weed-prone in suitable climates.
Conservation
No Clerodendrum species are currently profiled in the IUCN/ISSG Global Invasive Species Database. Some cultivated species nevertheless show weed potential — C. bungei in particular spreads aggressively by root suckers and by seed, and is reported as invasive in parts of its introduced range.
Cultural & Traditional Uses
Edible uses are not reported across the genus, and medicinal use is limited and uneven; for C. bungei, a decoction of the leaves is applied externally as an anodyne, anthelmintic, anti-inflammatory, and carminative. The name Clerodendrum itself reflects the genus's historical reputation: Linnaeus coined "chance-tree" partly because reports of the plants' medicinal usefulness in early sources varied so widely. Several species have also been planted around shrines and temples in Asia and carry religious associations.
Taxonomy
Clerodendrum L. was published in Linnaeus's Species Plantarum (1753, p. 637) and is the type-bearing genus of a clade traditionally assigned to Verbenaceae. Molecular phylogenetic work in the 1990s reassigned it — together with several allied former verbenaceous genera — to Lamiaceae, where it is now placed. GBIF records the genus as ACCEPTED with 410 subordinate names under the current backbone. Species totals vary by source: Wikipedia cites approximately 240 accepted species (with historical estimates spanning 150–450); PlantNET cites approximately 400.
