Description from Flora of China
Laurus cassia Linnaeus, Sp. Pl. 1: 369. 1753; Cinnamomum aromaticum Nees; Persea cassia (Linnaeus) Sprengel.
Medium-sized trees. Bark gray-brown, up to 13 mm thick when mature. One-year-old branchlets dark brown, terete, longitudinally striate, slightly pubescent; current year branchlets yellow-brown, ± tetragonous, longitudinally striate, densely grayish yellow tomentulose. Terminal buds small, ca. 3 mm; bud scales broadly ovate, acuminate, densely grayish yellow tomentulose. Leaves alternate or subopposite; petiole robust, 1.2-2 cm, adaxially plane or slightly sulcate on lower part, yellow tomentulose; leaf blade greenish opaque abaxially, green and shiny adaxially, narrowly elliptic to sublanceolate, 8-16(-34) × 4-5.5(-9.5) cm, leathery, sparsely yellow tomentulose abaxially, glabrous adaxially, triplinerved, midrib and basal lateral veins very elevated abaxially, conspicuously impressed adaxially, basal lateral veins subopposite, arising 5-10 mm above leaf base, arcuate-ascendant and evanescent below leaf apex, with numerous additional veins outside, these veins arcuately interconnected, transverse veins undulate and subparallel at a distance of 3-4 mm, elevated abaxially, inconspicuous adaxially, connected by veinlets only visible abaxially, base acute, margin cartilaginous and involute, apex slightly acute. Panicle axillary or subterminal, 8-16 cm, triplicate-branched, apex of branch bearing a 3-flowered cyme; peduncle as long as 1/2 of inflorescence, peduncle and rachis yellow tomentose. Pedicels 3-6 mm, yellowish brown tomentulose. Flowers white, ca. 4.5 mm. Perianth densely yellowish brown tomentulose outside and inside; perianth tube obconical, ca. 2 mm; perianth lobes ovate-oblong, subequal, ca. 2.5 × 1.5 mm, obtuse or subacute at apex. Fertile stamens 9, ca. 2.3 mm (of 1st and 2nd whorls) or ca. 2.7 mm (of 3rd whorl); filaments of 1st and 2nd whorls ca. 1.4 mm, complanate, dilated at upper 1/3, those of 3rd whorl ca. 1.9 mm, each with 2 orbicular-reniform glands at upper 1/3; anthers ovate-oblong, 4-celled; cells introrse (of 1st and 2nd whorls) or lateral-extrorse (of 3rd whorl). Staminodes 3, including stalk ca. 2 mm, sagittate-deltoid at apex; stalk slender, complanate, ca. 1.3 mm, villous. Ovary ovoid, ca. 1.7 mm, glabrous; style slender, as large as ovary; stigma small, inconspicuous. Fruit ellipsoid, ca. 10 × 7-8(-9) mm, black-purple when mature, glabrous; perianth cup in fruit shallowly cupuliform, ca. 4 mm, truncate or slightly dentate and up to 7 mm wide at apex. Fl. Jun-Aug, fr. Oct-Dec.
The dried bark is the source of the important spice cassia. The immature fruits are a source of cassia buds. An essential oil, called oil of cassia or oil of cinnamon, is obtained by steam distillation of the leaves and twigs; it is used as a flavoring agent. The plant is used medicinally as a carminative. It contains cinnamic aldehyde.
● Evidently originating in S China, now widely cultivated in tropical or subtropical areas of Fujian, Guangdong, Guangxi, Guizhou, Hainan, Taiwan, and Yunnan [cultivated in India, Indonesia, Laos, Malaysia, Thailand, and Vietnam].