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(Recorded in *Tang Bencao*)
[Flavor and Properties] Sweet, acrid, cold; slightly toxic.
[Indications] Primarily treats edema (swelling) and Hongjiao jiao (foot disease/gout), promotes urination and defecation, resolves phlegm, breaks up masses, eliminates accumulations, and dissipates carbuncles and swellings.
[Verification] It is stated: Originating from Jingzhou and Xiangyang regions, it is also found elsewhere, growing among fields, marshes, and pond banks. The plant grows several chi high. In the sixth and seventh lunar months, three leaves emerge from the stem, initially white then turning green.
When one leaf turns white, flowers subsequently bloom into spikes beside it, resembling Polygonum flowers, with a white color and slight fragrance. The seeds produced are small. The root is long, white, spongy, and jointed, with white rootlets resembling those of cattail (Pu Gen). Sprinkling the root juice on wheat flour aids in making yeast for brewing wine; the resulting wine is moistening, relieves summer heat, and possesses superior color, aroma, and taste. It can also be used to control Realgar (Xionghuang), stabilize Southern Lead (Nan Qian), and dry Cinnabar Mercury (Sha Meng).
[Verification] It is stated: Tao Hongjing claimed that there are three white spots on the leaves, hence the name "Sanbai" (Three Whites). Su Gong claimed there are three black spots on the leaves, not white, suggesting that ancients kept this secret, hiding the blackness as whiteness. Zang Qi stated that newly sprouted plants have no whiteness. Entering summer, half the leaves turn white like powder; farmers use this sign to transplant rice seedlings. If all three leaves are half-white, weeds appear, thus it is called "Sanbai". Li Shizhen stated that seedlings emerge in the eighth month; by the fourth month, the three leaves at the tip become white, changing from green to white, while the rest remains green and unchanged. Therefore, some say when leaves are initially white, eat wheat; when twice white, eat plums and apricots; when thrice white, eat millet. These are people who do not understand the true form and color of Sanbai. My family has planted this herb in front of the courtyard for over twenty years. I have observed that in the third month, seedlings emerge with leaves opposite each other like sweet potato leaves. After Minor Heat (Xiaoshu), new leaves emerge at the stem tips, pure white like powder, identical on both sides. Initially small, they gradually enlarge; upon enlargement, the leaf base turns green first, extending to the tip until the entire leaf is green. This process of leaf emergence occurs three times, after which no more leaves grow but weeds appear. The flower spikes are also white, and the rootlets are white; this constitutes the "Three Whites." If the weed-like state is removed before appearing, or if re-sprouting occurs in the sixth/seventh or eighth/ninth months, the leaves will only turn white when the season arrives. According to the Monthly Ordinances, after Minor Heat, encountering the third Geng day marks the beginning of the Three Fu days (Dog Days). This avoids the punishment of fire to preserve the golden virtue of calmness and balance. Sanbai Grass does not turn white during the Three Fu days but reveals its whiteness three times. Instead, at the juncture where fire and metal interact, it transforms heat into clarity and crispness. This is akin to igniting fire to create metal, without needing to seek another seed. Thus, it is suitable for treating conditions caused by summer heat injury where yang qi has not fully dispersed, and autumn dampness injury where descending functions are overly urgent.