Cassia is an aromatic bark, similar to cinnamon, but differing in strength and quality. Cassia bark is darker, thicker and coarser, and the corky outer bark is often left on. The outer surface is rough and grayish brown, the inside bark is smoother and reddish-brown. Cassia is less costly than cinnamon and is often sold ground as cinnamon. When buying as sticks, cinnamon rolls into a single quill while cassia is rolled from both sides toward the centre so that they end up resembling scrolls.

Cassia buds resemble cloves. They are the dried unripe fruits about 14 mm (1/2 in) long and half as wide. It is native to Burma and grown in China, Indo-China, the East and West Indies and Central America. Cassia is called kwei in the earliest Chinese herbal by Shen-nung (2700 B.C.). It reached Europe in classical times with Arabian and Phoenician traders and the buds were known in Europe in the Middle Ages.