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There are five types of Indigofera plants (Lan). Each has its own therapeutic indications. The leaves of Polygonum tinctorium (Poligonum Lan) resemble those of Persicaria (Liao). It flowers and forms spikes in the fifth and sixth lunar months; the flowers are small and light red, and the seeds also resemble those of Persicaria. It can be harvested three times a year, which is why ancient sages prohibited its over-cultivation. The leaves of Isatis indigotica (Song Lan) resemble those of Chinese cabbage (Song); the leaves of Strobilanthes cusia (Ma Lan) resemble those of Ixeris (Ku Ju), which is also known as large-leaf winter indigo, commonly called Ban Lan. The flowers and seeds of these two indigos are similar to those of Polygonum tinctorium. The stems of WU Lan are long like Artemisia (Hao) with white flowers, cultivated by people in Wu region. The stems of Indigofera tinctoria (Mu Lan) are long like Cassia obtusifolia (Jue Ming); the taller ones reach three or four chi, with leaves distributed like those of Sophora japonica (Huai). It blooms pale red flowers in the seventh lunar month and produces pods about one cun long. Its seeds are also like those of Cassia obtusifolia but smaller, distinctly different from other indigos, yet all yield indigo dye equally. (Cited from Li Shizhen)

Indigo Seeds (Lan Shi)
Only the seeds of Polygonum tinctorium are used medicinally, harvested in the fifth and sixth lunar months.
Taste: bitter, sweet. Nature: cold. *Shennong Bencao Jing* states it resolves various toxins. *Mingyi Bielu* states it benefits the five zang organs, harmonizes the six fu organs, unblocks joints, and treats qi stagnation in the meridians and collaterals.
Note: Lan Shi belongs to the Polygonum Lan category.
Indigo Leaf Juice
Derived from Polygonum tinctorium.
Taste: bitter, sweet. Nature: cold. Applied to the "five centers" (palms, soles, and chest), it stops irritability and restlessness, kills various drug poisons, and resolves wild wolf tooth poison, She Wang poison, as well as Cinnabar (Zhusha) and Arsenic (Pishi) poisons. Someone suffering from spleen disease with vomiting... thus Indigo is regarded as... [Text fragment].

Ban Lan Gen (Isatis Root)
Refers to the root of Strobilanthes cusia (Ma Lan).
Taste and nature: bitter, cold. Treats blood stasis in women. (Bake the whole plant including roots, crush, and take one qian bi with wine.) Treats epidemic heat-toxin (Tianxing Redu). Puji Xiaodu Yin uses it to treat major... [Text fragment]. Epidemic heat-toxin causing mental restlessness and irritability: take one spoonful of Indigo Paste (Lan Dian), mix with one cup of fresh well water, and drink. For acute gan erosion of nose and mouth (severe ulceration), where death seems imminent within days: apply Indigo Paste thoroughly to the affected area, ten times daily and four times at night, until healed.

[General Discussion]
Although various indigos differ in morphology, their properties and tastes are not far apart; all can resolve toxins and clear heat. Only the leaves of Indigofera tinctoria (Mu Lan) seem slightly weaker in efficacy, while Indigo Seeds specifically select those from Polygonum tinctorium.
Qing Bu (Indigo-dyed cloth / Indigo products)
Resolves various external toxins. Treats epidemic toxic heat (Tianxing Fandu), pediatric fever with erysipelas (Dan Du): soak in well water, extract the juice, and drink. Mix the extracted juice with ginger juice to stop... [Text fragment]. Burn to ash and apply to chronic malignant sores that have not healed for years. Burn to ash and take with wine to treat cracked lips with sores and bad breath; combine with ointment for topical application. To prevent water entry into malignant sores, burn Qing Bu mixed with wax in a smoke tube for fumigation; the treated area does not rot when submerged. For ulcerated sores, use aged mugwort (Chen Ai) 5 qian, realgar (Xionghuang) 2 qian, roll Qing Bu into a large moxa cone, and ignite... [Text fragment].