Harvesting, Processing and Storage Methods of the Chinese Medicinal Herb White Peony Root

White peony root (Paeonia lactiflora) can be harvested 3 to 4 years after planting. Harvesting too early gives a low yield, while harvesting too late leaves the root core hollow, which not only lowers the yield but also affects quality. Generally, three years is enough for harvest. The harvesting season also has a considerable effect on the quality and yield of the medicinal material. According to the specific conditions of each producing area, the harvest period should not begin earlier than late June, otherwise the yield will be affected, and should not be later than early October, otherwise the starch in the root will be converted and the root will not be firm after drying, and its weight will also be reduced.

At harvest, first cut off the stems and leaves, dig away the soil around the plant, and turn and dig to a depth of about 0.33-0.5 m (1-1.5 chi), then dig out the soil at the tail end; this prevents the main root of the peony from being broken during digging. After the main roots have all been dug out, shake off the soil, transport them indoors, cut off the peony roots (set the root heads aside separately for use as planting material), trim off the lateral roots or fibrous roots, smooth down the raised surfaces, cut off the head and tail, and sort them into three grades: large, medium and small. Pile them indoors for 2-3 days, turning the pile twice a day, to promote evaporation of moisture from the peony roots so that the texture becomes soft and easy to process.

Although the processing methods for peony root differ, they can generally be divided into four steps: trimming, whitening by rubbing, boiling, and drying. Some areas use the method of first rubbing white (scraping the skin) and then boiling, while other areas use the method of first boiling and then scraping the skin.

1. Trimming

Use a small knife to cleanly shave off the fibrous roots from the peony roots (never pull them off by hand, otherwise many sunken marks will be left, affecting quality), cut off the head and tail, and shave flat the two ends and any protruding parts of the surface so that the surface is level.

2. Whitening by rubbing

First put the trimmed peony roots into a basket and soak them in running water or a pond for 1-2 h so that the skin is easy to rub off. However, the soaking time should not be too long, otherwise part of the root bark will come away. Then lift out the peony roots and place them on a wooden bed for rubbing. The wooden bed is 65-70 cm high, 85-100 cm wide and about 200 cm long, with side boards 17-20 cm high on both sides. Two people stand on each side of the wooden bed, each holding a wooden mallet, and the two ends are pushed back and forth crosswise. During pushing, a certain amount of yellow sand is added to increase friction. After the surface skin has been rubbed clean, wash off the sand and mud with water and soak in water until boiling.

3. Boiling

The peony roots should be boiled on the same day they are soaked; the soaking time is about half a day and must not be too long. First heat the water in the pot (an aluminum pot is best) to 80-90°C, then put the peony roots into the pot, with the amount of water just enough to submerge the peony roots, and about 15-25 kg of peony roots per pot. First keep the pot tightly closed for 5 min, then open it and turn the roots over from top to bottom so that they are heated evenly. Control the fire so as to keep the water in the pot at a gentle boil. If the water is found to be boiling too vigorously, add cold water promptly and turn the roots over from top to bottom quickly so that the heat is even, because if the water boils too vigorously, the rapid heating will cook the surface of the peony roots while the sap inside has not been fully released and is still raw. The boiling time should depend on the size of the peony roots: generally 5-8 min for small roots, 8-12 min for medium-thick roots, and 12-15 min for larger roots. The properly boiled peony roots should be quickly taken out of the pot and sent to the drying yard to be spread out for sun-drying.

4. Drying

Send the boiled peony roots immediately to the drying yard and spread them out for sun-drying; they must not be piled and left for too long. If they cannot be spread out in time that same day, spread them in a well-ventilated place and never pile them up, otherwise the surface of the peony roots will become slippery and sticky the next day, affecting quality. When spreading them out to dry, first spread them in a thin layer and expose them to strong sun for 1-2 h, then gradually pile the peony roots thicker and continue sun-drying, so that the surface slowly shrinks; the peony roots dried in this way have fine, delicate surface wrinkles and a good color.

For packaging dried peony roots, fine bamboo baskets are generally used. First pad the four corners of the bamboo basket with palm fiber or bamboo shoot sheaths, then put the sun-dried peony root into the basket. Gunny sacks may also be used for packaging. Store in a ventilated, dry place, strictly guarding against moisture; check frequently for moisture and mold, and turn and sun-dry them regularly. Turning and sun-drying should be done in mild sunlight; avoid exposure to blazing sun, so as to prevent discoloration and reddening. To prevent insect damage and mold during storage of white peony root, the peony roots can be fumigated with volatile oil before storage. The method is to fumigate the peony roots with cubed litsea (Litsea cubeba) or clove volatile oil in a ratio of 10000:1 in a sealed state for 6 days.