Inherently being called a regal flower associated with the image of the Nguyen Dynasty in Hue, the annual blooming season of Firmiana simplex (also known as Chinese parasol) flowers is in late March and April, creating picturesque images in the space of Hue Imperial Citadel.

Sam Bo Chinh (Abelmoschus sagittifolius) starts to be sowed in February and its flowering time is from June to July. However, the time of August - September is its blooming season. Due to the continuous blooming of Bo Chinh ginseng Flowers, the work of flower harvest lasts for 2 months.