Qing Hao (Artemisia annua)

An easily grown plant, succeeding in a well-drained circumneutral or slightly alkaline loamy soil, preferring a sunny position[1, 200]. Plants are longer lived, more hardy and more aromatic when they are grown in a poor dry soil[245]. A fast-growing annual plant, it is tall but neat in habit with a handsome fragrant foliage and is useful for filling gaps at the back of a border[238]. It has become a weed of waste places in many areas of the world[43]. The plant is extremely vigorous and essentially disease and pest free[269]. Qing Hao is a determinate short-day plant. Non-juvenile plants are very responsive to photoperiodic stimulus and flower about two weeks after induction. The critical photoperiod seems to be about 13.5 hours, but there are likely to be photoperiod x temperature interactions. In Lafayette Indiana, USA (40¡21’N) plants flower in early September with mature seeds produced in October. The plant is not adapted to the tropics because flowering will be induced when the plants are very small[269]. Most collections of artemisia derive from natural stands with highly variable artemisinin content, some as low of 0.01%. Selections from Chinese origin vary from 0.05 to 0.21%. Swiss researcher N. Delabays reports a clonal selection derived from Chinese material which produces 1.1% artemisin but is very late flowering; proprietary hybrids have been obtained with somewhat lower content but flower earlier[269]. Members of this genus are rarely if ever troubled by browsing deer[233].