By Eric Brand

In school, we learn that Bai Shao (Paeoniae Radix Alba) and Chi Shao (Paeoniae Radix Rubra) were not differentiated in ancient times. For example, classical texts from the Han dynasty such as the Shang Han Lun (“On Cold Damage”) and the Jin Gui Yao Lue (“Essential Prescriptions of the Golden Coffer”) only referred to Shao Yao, which is a basic term for peony that doesn’t differentiate between red peony (Chi Shao) and white peony (bai shao). When did these two medicinals start becoming differentiated, and which forms are best in classical formulas such as Gui Zhi Tang and Gui Zhi Fu Ling Wan?

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The first time that the terms red (chi) and white (bai) appeared in the context of Shao Yao was in Tao Hong-Jing’s annotated version of the Shen Nong Ben Cao Jing (“The Divine Husbandman's Herbal Foundation Canon”), which was compiled in about 500 CE. Nonetheless, Bai Shao and Chi Shao continued to be undifferentiated throughout the materia medica literature of the Sui (581-618 CE) and Tang (618-907 CE) dynasties, and the two only really started to become separated around the end of the Tang dynasty or the beginning of the Song dynasty (960 CE).

Major formula texts from the Song dynasty such as the Tai Ping Sheng Hui Fang and the Tai Ping Hui Min He Ji Ju Fang tended to differentiate Bai Shao and Chi Shao, and the understanding of their effects tended to deepen. Many formulas for dispelling evil tended to use Chi Shao, while formulas for supplementing vacuity tended to use Bai Shao. The text Zhu Jie Shang Han Lun (“Annotated Cold Damage”), which was written in 1144 CE by Cheng Wu-Ji, stated that “Bai [Shao] supplements while Chi [Shao] drains; Bai [Shao] contracts while Chi [Shao] disperses.” These works from the Song and Jin dynasties had a major impact on the clinical perceptions of later generations of practitioners. By the Ming dynasty, several different materia medica texts contained separate entries for Bai Shao and Chi Shao, and some of the books that still grouped them together under the name Shao Yao clearly differentiated the two forms.

Based on Tao Hong-Jing’s description of their growing environments, we can assume that the wild product was most prominent in ancient times. By the 11th century, an author in the Song dynasty referenced the widespread cultivation of Shao Yao, which shows us that the cultivated product has been in use for at least a thousand years or so.

In the modern day, the official plant source for Bai Shao is Paeonia lactiflora Pall. By contrast, Chi Shao can be officially derived from two plants: Paeonia lactiflora Pall. and Paeonia veitchii Lynch. The latter plant only produces Chi Shao, while the former produces both Chi Shao and Bai Shao (Chi Shao can also be derived from a number of other peony species, but the two listed above are the “official” ones).

Even though both Bai Shao and Chi Shao can come from Paeonia lactiflora, they differ in terms of their growing environment and processing method. If the Paeonia lactiflora is wild, it is Chi Shao. If it is cultivated and subjected to Pao Zhi (processing), it is Bai Shao. Bai Shao is boiled and the skin is removed, while Chi Shao leaves the skin intact. Some of the active constituents are higher in the skin, so there is a significant difference between Bai Shao and Chi Shao in terms of their chemistry.

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