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[Shangpin Category of the Classic of Materia Medica]
[Flavor and Nature] Bitter, cold, non-toxic.
[Indications] Primarily resolves various toxins, kills gu poison (parasitic poisoning), zhu ghost (infectious diseases attributed to spirits), and venom from insect or snake bites. Long-term consumption prevents graying of hair and lightens the body.
[Analysis] It is stated: Grows in the plains and marshes of He Nei. Some are planted in garden beds with ridges. There are five types, among which the fruit of Polygonum tinctorium (Láolán) is specifically used. Láolán has leaves resembling Polygonum species, sprouts in March, flowers and forms spikes in May with pale red flowers; its flowers and fruits resemble Polygonum. It can be harvested three times a year. Therefore, the ancient kings ordered people not to harvest indigo plants for dyeing during midsummer. Zheng Xuan said: This is to avoid damaging the vital energy of growth. One type is Song Lan (Pine Indigo), with leaves resembling Chinese cabbage. Another is Ma Lan (Horse Indigo), with leaves resembling Sonchus oleraceus (Kusheng); this is what Guo Pu referred to as "Da Ye Dong Lan" (Large-leaf Winter Indigo), commonly known as Banlangen (Isatis Root). Its flowers and fruits are identical to Láolán, differing only in seedlings and leaves. Another type is Wu Lan, with stems like Artemisia and white flowers, cultivated by people in Wu; another is Mu Lan (Tree Indigo), with stems like Cassia obtusifolia, growing three to four chi high, branching out with leaves resembling Sophora japonica (Huai tree), blooming with pale red flowers in July, forming pods about one cun long, clustered like small bean pods, seeds resembling Cassia seeds but smaller, distinctly different from other indigos, yet producing indigo dye similarly. Additionally, there is Gan Lan (Sweet Cabbage), edible as a vegetable. The method for making indigo paste involves digging a pit to bury a vat, soaking indigo plants overnight, adding calcined gypsum (Duanshi), stirring frequently over ten thousand times, clarifying, removing water, resulting in blue pigment. It can also be dried for storage to dye cyan/green. The foam skimmed off after stirring and dried in shade is called Dianhua (Indigo Flower), which is the Qingdai (Indigo Naturalis) sold in markets. This is produced through processing with calcined gypsum; do not use it lightly. People mistakenly believe that because it is blue, it enters the Liver to clear heat and resolve toxicity, which is highly erroneous. True Qingdai comes from Persia; since it is unavailable, it is better to use Lanshi (Indigo Fruit), or Lanye (Indigo Leaf), or pure natural juice without impurities.
Bo Yi commented: Long-term consumption of Lanshi prevents hair graying. This is likely because Spring Qi resides in the head; using its blue color assists the generation of Spring Qi, naturally benefiting the head and hair. The Liver governs color; blue enters the Liver. Thus, for any disease manifesting with color changes, it is highly appropriate. Such as acne/eruptions, erysipelas, macules, blood disorders, five-colored dysentery, red or yellow eyes, internal heat in the five Zang organs manifesting first on the face and cheeks. Its power can enter the Liver via the Xun (Wind/Wood) pathway. It controls the Spleen (Earth), serving as a mild agent to calm heat. Observing the cases of Ban Zhizhu (Spotted Spider), Yingsheng Chong (Echoing Worm), and Yegé Chong (Choking Worm) is also remarkable. One often sees indigo farmers sweeping insects daily; if not swept, they are eaten completely. How can these breeding grounds for insects instead kill them? This embodies the principle of Xun entering the nature. Human digestion follows Qi dynamics like a gathering fire; things thrown in disappear. Indigo enters the Stomach, becoming food for insects, causing them to gather. As Indigo follows Qi dynamics, insects follow suit. Once entering the Qi mechanism, there is no escape. One must be cautious regarding preferences in favorable conditions.
[Eulogy] It is said: Lan represents life, symbolizing the color of all things when growing. Fermented into indigo paste, the color surpasses the mother (Qing chu lan er qing yu lan - Blue comes from indigo plant but is bluer than the plant). The Liver governs color, and its color is blue, so it should enter the Liver. It can serve as a tonic for the Liver, or as a kidney-tonic for the Liver, due to its juicy nature and cold qi; it can also serve as a heart-medication for the Liver, due to its bitter taste and penetrating nature. Through its color, taste, nature, and qi, it obtains the function of Southeast Xun Wood, thereby cleansing and ordering all things. It can be planted in all four seasons and harvested three times a year, meaning Sheng Yang (Generating Yang) is predominant, while the cycle of Jiazi belongs solely to Spring. Hence, Lan derives from the character Jian (Monitor), meaning observing the four directions. Gu, Zhu, and ghosts are all gathered killing energies, belonging to dead Yin and unclean entities. Lan can enter via Xun and share spring vitality with all things, thus purifying the killing energy, warming it like the benevolence of Spring, allowing blue to emerge. Long-term consumption nourishes the Liver; when the Liver is nourished, hair becomes lustrous, movement and rotation satisfy desires. Lan Dye and Qingdai are merely extensions; they are not as comprehensive as Lanshi, which contains the true, endless treasure.
(Xun governs entering its nature and temperament. Cleansing and ordering all things is its efficacy. 'Jie' can mean cleanliness or the act of washing/cleaning; where there is dampness and filth, insects breed.)