Grewia is a genus of flowering plants in the mallow family (Malvaceae), comprising woody species that range in habit from small shrubs to small trees. Plants of the World Online accepts about 277 species in the genus, while the broader GBIF taxonomic backbone records roughly 275–383 descendants once subspecies and synonyms are included. The genus is widespread across the tropical and subtropical Old World, with members native to Africa, Madagascar, the Middle East, the Indian subcontinent, China, Southeast Asia, northern and tropical Australia and many Pacific islands such as Fiji, Samoa and Vanuatu. Australia alone harbours around 20 native species.
Members of Grewia tend to share a fairly recognisable floral pattern, with bisexual flowers whose petals and stamens are borne above a small disc, followed by a distinctive drupe — a small, hard-stoned fruit that in many species is sweet, juicy and slightly astringent. It is this combination of edible drupes and tough, fibrous bark that has given the genus a long history of human use. Several species, most famously the South Asian phalsa or falsa (Grewia asiatica), are grown commercially or locally for their refreshing summer fruit, while the southern African crossberry (Grewia occidentalis) is widely cultivated as an ornamental shrub.
Taxonomically, Grewia was established by Carl Linnaeus in 1753 in Species Plantarum, where he named it in honour of the English botanist and pioneering plant anatomist Nehemiah Grew (1641–1712). It was long treated in the family Tiliaceae (or, in some classifications, Sparrmanniaceae), but modern molecular phylogenetic work now places it in an enlarged Malvaceae, where it is the type genus of subfamily Grewioideae and tribe Grewieae. POWO recognises ten heterotypic synonyms at genus rank, including Arsis, Chadara, Mallococca and Vincentia, reflecting a complex nomenclatural history across continents.
Ecologically Grewia occupies a remarkable variety of niches across the warm parts of the Old World, from open African savannas and dry thornveld to monsoonal forests, island ecosystems and seasonally dry tropical scrub. The combination of edible fruit, tough fibre, useful timber and ethnobotanical importance — bark from G. polygama and G. eriocarpa, for instance, is used in the traditional Burmese shampoo tayaw kinpun, and various species feature in folk remedies for digestive and skin complaints — has made Grewia one of the more economically and culturally significant woody genera of the palaeotropics.
Etymology
The genus Grewia was established by Carl Linnaeus in 1753, in the first edition of Species Plantarum. Linnaeus named it in honour of the English botanist Nehemiah Grew (1641–1712), who was one of the leading plant anatomists and microscope researchers of his era. The name has remained in continuous use ever since, with Grewia L. recognised today as the accepted genus name by both POWO and the GBIF taxonomic backbone.
Distribution
Grewia has a broad palaeotropical distribution. POWO records the native range as the tropical and subtropical Old World extending into the Pacific, with species occurring widely across sub-Saharan Africa, Madagascar and surrounding island groups, north into Algeria and across the Middle East and Afghanistan, throughout the Indian subcontinent and Southeast Asia, in China, and on numerous Pacific islands including Fiji, Samoa and Vanuatu. In Australia the Atlas of Living Australia recognises about 20 native species of the genus, including Grewia australis, Grewia latifolia and Grewia scabrella. The genus is absent as a native element from the Americas.
Taxonomy
Grewia sits in the mallow family, Malvaceae, in the order Malvales. Older floras commonly placed the genus in Tiliaceae or, less often, in Sparrmanniaceae, but it is now treated as the type genus of subfamily Grewioideae and tribe Grewieae within an expanded Malvaceae. Plants of the World Online accepts approximately 277 species in the genus, while the GBIF backbone — which includes infraspecific taxa and synonymy — records 383 descendants. POWO also lists ten heterotypic generic synonyms, including Arsis, Chadara, Mallococca and Vincentia, reflecting a long history of regional taxonomic treatments. The genus was first published in Species Plantarum on page 964.
Ecology
Across its range Grewia occupies a wide variety of habitats, from African savannas and dry thornveld to seasonally dry tropical forests and Pacific island ecosystems. POWO describes the genus as occurring in diverse ecological niches across tropical and subtropical environments, with representation in savannas, forests and island ecosystems across multiple continents. Many species are characteristic of open, seasonally dry, sun-exposed habitats, which is consistent with the genus's reputation for drought tolerance.
Cultivation
Cultivation requirements vary considerably across the genus, but published horticultural notes for cold-hardy species (such as Grewia biloba var. parviflora) indicate that plants tolerate a wide range of soil textures — light, medium or heavy — and a pH range from mildly acid to alkaline. They grow in either full sun or semi-shade and prefer consistently moist conditions. Hardiness for the few temperate-zone members is roughly USDA zones 5–9 / UK zone 6, with one report citing cold tolerance to about -30 °C; tropical and subtropical members are correspondingly more frost-tender. Several species, particularly the southern African Grewia occidentalis (crossberry), are also widely grown as ornamental shrubs.
Propagation
Genus members are typically propagated from seed, sown in late winter in a cold frame; seedlings are pricked out into individual pots and grown on in a greenhouse through their first winter before being planted out. Layering is also reported as a viable vegetative propagation method.
Cultural Uses
Grewia has a long and varied history of human use across its native range. The most economically important food species is the South Asian phalsa (Grewia asiatica), whose small, refreshing, slightly astringent drupes have local commercial importance and are particularly popular as a summer fruit. In Myanmar the bark of Grewia polygama and Grewia eriocarpa is a key ingredient in the traditional shampoo tayaw kinpun. Various species also feature in folk medicine for the treatment of upset stomachs and certain skin and intestinal infections.
Conservation
At the genus level Grewia is not currently flagged as invasive by the IUCN Global Invasive Species Database, which reports that no Grewia species are present in its archive. Conservation assessments are carried out by IUCN at the species level rather than the genus level, so genus-wide status statements are not available from these sources.
History
The genus has been recognised under the name Grewia continuously since Linnaeus described it in Species Plantarum in 1753, dedicating it to the English botanist and microscopist Nehemiah Grew. POWO cites the original publication as Sp. Pl.: 964 (1753). Over the centuries the genus has migrated between several family-level placements — initially Tiliaceae, sometimes Sparrmanniaceae, and now an expanded Malvaceae — but the genus circumscription itself has remained broadly stable.
