Vietnam is the world's third-largest producer and exporter of cassia in terms of output. Cassia is grown on a large scale in the mountainous areas of northwest Vietnam, with an area of 200,000 ha, accounting for 95% of the total cassia growing area. The growing area in the South Central Coast accounts for 5%. Growing cassia is currently a livelihood for hundreds of thousands of households in remote provinces, and at the same time contributes to the socio-economic development of many localities in Vietnam.
There are 3 harvest seasons for cassia leaves and twigs for distillation. Season 1 is from April to early July. Season 2 is from late July to mid August and lasts only 15-20 days. Season 3 from is mid-September to December.