Premna is a genus of flowering plants in the mint family, Lamiaceae (order Lamiales), first described by Carl Linnaeus in 1771 in Mantissa Plantarum. The genus is nomenclaturally conserved and encompasses roughly 200 species distributed across the Old World tropics and subtropics — from tropical Africa and the Arabian Peninsula through the Indian Subcontinent, Southeast Asia, southern China, northern Australia, and numerous islands of the Pacific and Indian Oceans.
Members of the genus are most commonly trees, shrubs, or subshrubs, growing erect or rarely in a climbing habit. Branches are usually terete and typically bear distinctive round or elliptic yellowish glandular lenticels. The leaves are simple and opposite, with margins ranging from entire to 3–5-crenate. Inflorescences are diverse in form, appearing as terminal trichotomous panicles, leaf-opposed cymes, clusters, paniculate corymbs, or spikelike thyrses. The flowers are small; the calyx is roughly cup-shaped or campanulate, with teeth that are equal or distinctly 2-lipped. The corolla has a short tube with 4 (or obscurely 5) spreading lobes that range from subequal to clearly 2-lipped. Four stamens are typically present, often didynamous. The fruit is a small drupe, usually enclosing a 4-locular pyrene.
The genus is particularly diverse in South and Southeast Asia, with 46 species recorded in China alone. Widely distributed species such as Premna serratifolia range from East Africa across the Indian Subcontinent and Southeast Asia to northern Australia and Pacific island groups. The genus was formerly placed in the family Verbenaceae but is now firmly positioned in Lamiaceae following molecular phylogenetic revision.
Distribution
Premna is widespread across the Old World tropics and subtropics, occurring in tropical and subtropical Africa, the Arabian Peninsula, the Indian Subcontinent, southern and eastern Asia (including 46 species in China), Southeast Asia, northern Australia, and island groups of the Pacific and Indian Oceans. The species Premna serratifolia exemplifies the broad reach of the genus, ranging from East Africa to Polynesia.
Taxonomy Notes
The genus was established by Linnaeus in Mantissa Plantarum (1771) and is nomenclaturally conserved (nom. cons.). The synonym Pygmaeopremna Merrill has been subsumed within Premna. The genus was historically treated within Verbenaceae but modern molecular systematics places it unambiguously in Lamiaceae (order Lamiales). GBIF recognises 36 accepted infrageneric taxa; Flora of China accounts for about 46 species within China's borders alone, out of an estimated 200 species worldwide.
