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*Rehmanniae Radix Praeparata* (Shu Dihuang, 熟地黄), grows in the rivers and marshes of Xianyang; those from loess soil are superior. It is now found everywhere, with the best quality coming from Tongzhou. Leaves emerge in February, spreading along the ground, resembling *Plantaginis Semen* (Cheqiancao, 车前草). The leaves have wrinkles and are not smooth. Plants may grow up to over a chi (approx. 33 cm) or as low as three to four cun (approx. 10-13 cm). The flowers resemble those of *Brassica napus* (Youcaihua, 油菜花) and are reddish-purple, though yellow varieties exist. The fruit resembles that of *Forsythiae Fructus* (Lianqiao, 连翘), containing very fine seeds that are sandy-brown. The root resembles a human finger, is uniformly yellow, and varies in thickness and length. Roots are harvested in February and August, steamed for two to three days until soft, then dried in the sun to produce *Radix Rehmanniae Preparata* (Shu Dihuang, 熟地黄). Those dried in the shade are *Radix Rehmanniae Recens* (Sheng Dihuang, 生地黄). Cultivation is easy; roots take hold upon entering the soil. One theory states that ancient texts recommended loess soil for planting. This is no longer the case; it thrives best in fertile, loose soil, yielding larger and juicier roots. The method involves weaving reed mats into circular shapes like wheels, over one zhang (approx. 3.3 m) in diameter, filling them with soil to form a mound. Another level is built on top using reed mats and soil, reducing the diameter by one chi compared to the base. This is repeated for several levels, resembling a pagoda. Root sections with many nodes are cut into one-cun lengths and planted on the terraces, filling each layer. Water is applied daily to promote lush growth. At the Spring or Autumn Equinox, harvest from the upper layers. The roots grow large without breaking because they are undamaged. After harvesting, dry in the sun. Prepared *Radix Rehmanniae* is of the highest quality, originating from Tongzhou; it is lustrous, moist, sweet, and delicious. Such high-quality prepared root is unknown in the South. Instead, fresh *Radix Rehmanniae* herbs are smoked until black, then washed to remove soot, revealing the white interior. Current drying methods: Take 30-20 jin (approx. 15-10 kg) of fleshy *Radix Rehmanniae*, wash thoroughly, remove fine roots and short nodal sections, retaining 20-30 jin. Crush and press to extract juice, pour into silver or copper vessels, add fleshy *Radix Rehmanniae* slices, soak and filter repeatedly to ensure penetration. Steam over rice for three to four cycles, alternating soaking/filtering and steaming. Finally, dry until all juice evaporates. The resulting root should be glossy black like lacquer and sweet as maltose. Store in porcelain containers, as its oily texture prefers controlled humidity. To distinguish quality, newly harvested roots are soaked in water. Those floating are called *Tianhuang* (Heaven Yellow) and are unusable. Those half-sinking are *Renhuang* (Human Yellow) and are inferior. Those sinking completely are *Dihuang* (Earth Yellow) and are best. For immortal dietary regimens, harvest roots, wash, crush, and press for juice. Boil until slightly thick, add white honey, boil again until pillable. Take thirty pills the size of *Pharbitidis Semen* (Wutongzi, 梧桐子) with wine in the morning, three times daily. Pills can also be made with *Jujubae Fructus* (Qingzhou Zao, 青州枣) flesh. Alternatively, make an electuary with dried root powder. In April, harvest fruits, dry in shade, sieve into powder, and administer with water using a coin-sized measure (*Qianbi*, 钱匕); efficacy is equivalent. The flower is called *Disuihua* (Di Sui Flower). *Yannian Fang* records two single-herb methods. It is also a crucial herb for treating trauma and metal wounds. *Zhouhou Fang*: For fractured limbs, shattered bones, and dislocated tendons, crush fresh *Radix Rehmanniae*, heat it, wrap around the injury, secure with bamboo splints, bind tightly to prevent movement. Change once daily for a day and night, up to ten times, leading to recovery. Cui Yuanliang's *Haishang Fang*: Treats all types of heart pain, new or old. Use only fresh *Radix Rehmanniae*. Amount depends on food intake. Crush, press for juice, mix with flour to make cold noodles (*Lengtiao*, 冷淘), or eat cold. After some time, worms approximately one chi long will be expelled, with heads resembling geckos, curing the disease permanently. A past patient suffered for three years, regretting deeply. On his deathbed, he instructed family to dissect him after death to remove the cause. They found a worm, kept it in a bamboo joint, fed it with every meal, including when he ate *Dihuang* cold noodles, causing it to rot. This led to the formula. Liu Yuxi's *Chuanxin Fang*: Records this event. In the 10th year of Zhenyuan, Cui Kang, a Commissioner of Palace Communications, had a daughter suffering from severe heart pain nearing death. She ate *Dihuang* cold noodles and vomited an object about one inch square, resembling a toad, without eyes or feet, but with a faint mouth-like opening. She was cured, having been afflicted by this creature. Do not add salt to cold noodles.