Detailed Explanation of Key Points for Authentic Cultivation Techniques of Gastrodia elata

Gastrodia elata, also called red arrow, dingfengcao, and water potato, is a perennial herb of the genus Gastrodia in the orchid family. It is a precious medicinal material for treating nervous system diseases. The medicinal part is the underground tuber. Gastrodia elata is sweet in taste and neutral in nature, and has the effects of calming liver fire, tonifying qi and relieving convulsions, nourishing the liver, and relieving spasms. Artificially authentically cultivated Gastrodia elata and wild Gastrodia elata show no obvious difference in morphology or efficacy, so developing artificial cultivation of Gastrodia elata is an effective measure to address the increasing scarcity of wild Gastrodia elata. Authentic tunnels (or caves) are warm in winter and cool in summer, suitable for the growth and development of Gastrodia elata, and are an ideal place for cultivating Gastrodia elata. Cultivating Gastrodia elata in tunnels gives high yield, has simple techniques, requires little labor, has low cost, is easy to manage, and can avoid human, livestock, disease, and pest damage to a relatively large extent.

Because Gastrodia elata cannot nourish itself, its growth must be supplied with basic nutrients by Armillaria mellea. Armillaria mellea belongs to the order Agaricales, family Agaricaceae, genus Agaricus, and is a fungus used as both food and medicine. It has a special symbiotic relationship with Gastrodia elata. During artificial cultivation, Armillaria mellea must be cultured on suitable wood as a nutritional substrate.

1. Selection of the tunnel The tunnel for cultivating Gastrodia elata should have the following conditions: ① The tunnel should have a low-temperature period of more than one month above 10°C in winter; ② The summer temperature should not exceed 28°C, to facilitate the summer growth of Gastrodia elata; ③ Both ends of the tunnel should have closable openings to help regulate the temperature and humidity inside the tunnel. Generally, shallow tunnels are preferable. Before cultivation, clean and level the tunnel, open small water ditches along both walls, preferably whitewash the inner walls, and fumigate with sulfur or formaldehyde for sterilization.

2. Cultivation time The sowing period is January to February, when the tunnel temperature is generally around 12°C, Armillaria mellea can grow, and Gastrodia elata is still in dormancy; by March to May (when the temperature rises above 15°C), Gastrodia elata begins to germinate while Armillaria mellea has already grown well and has established a symbiotic relationship with Gastrodia elata.

3. Cultivating fungal material Build a fungal material pit 2 to 3 months before planting Gastrodia elata. The method is as follows: lay bricks or cobblestones on the ground layer, leaving 1 cm gaps between bricks to facilitate ventilation and drainage, then build a brick pool 1 m wide and 45 cm high on top, with the length determined by the amount of fungal material. The upper and lower bricks do not need to be bonded, and 1 cm gaps should be left between the left and right bricks. The filler is a mixture of rice husk and yellow sand (volume ratio 1:1), with a water content of about 30%. First spread 6 cm of filler, then lay new wood segments cut with fish-scale notches and with a water content of 40%, 80 cm long. Place several pieces of inoculated fungal material beside the new wood segments and fill the gaps with filler. Lay a second layer in the same way, and up to 4 to 5 layers may be laid. Finally cover with about 4 to 5 cm of filler with a water content of about 50%. Check the filler water content once every 3 to 5 days. If the water content is insufficient, sprinkle water to maintain it. At ordinary times, loosen the soil for ventilation to favor the growth of rhizomorphs. Well-cultivated fungal material will have a large number of rhizomorphs protruding from the ground.

4. Cultivating Gastrodia elata In tunnels, brick-built heap pits are generally the most practical for cultivation. The construction method of the heap pit is the same as that of the fungal material pit. Spread 6 cm of a mixed filler of sawdust (or rice husk) and sand (volume ratio 1:1) at the bottom of the pit, and place fungal material side by side, with 3 to 4 cm between fungal materials. Fill the gaps with filler so that the fungal material is half buried. Place one seed Gastrodia elata at both ends and at each fish-scale notch of every piece of fungal material. Place covering material directly above the fungal material. The thickness should be such that the fungal material is shallowly buried. In this way, 2 to 3 layers can be laid in total. Water each layer thoroughly, and finally cover with 12 cm of covering material and water thoroughly, with the water content such that the surface does not dry out.

Tunnel planting of Gastrodia elata may use sexual reproduction. New seeds of Gastrodia elata can be scattered on the fungal material, and after one and a half years, arrow Gastrodia, white Gastrodia, and rice Gastrodia can be produced. Asexual reproduction is usually carried out from November of the current year to March of the following year. Generally, white Gastrodia and rice Gastrodia are used as seed Gastrodia and planted on both sides of the fungal material. The seed Gastrodia density is 300 g/sq m. Usually the upper layer produces more arrow Gastrodia, and the lower layer produces more white Gastrodia.

Because the tunnel temperature is stable but humidity varies greatly, controlling the humidity of the substrate and air is key. Generally, from November to March of the following year the climate is dry, so a layer of rice straw can be spread on the rice husk and river sand material, and water can be sprinkled with a watering can to replenish moisture. From August to October the tunnel is damp; a fan can be used to blow air and increase ventilation and air exchange for regulation.

In the early stage of Gastrodia elata cultivation, because Armillaria mellea and Gastrodia elata have not yet combined and Gastrodia elata has not yet sprouted, the filler water content should be controlled at about 25%. Too high a water content will affect the growth of Armillaria mellea and cause the seed Gastrodia to rot. In the middle stage, because Gastrodia elata has sprouted and is growing rapidly, water demand gradually increases. At this time the filler water content should reach about 50%, and watering should be light and frequent. If the filler becomes compacted after watering, loosen the soil in time. After arrow Gastrodia forms, humidity should be reduced to prevent rot.

The causes of Gastrodia elata rot include: repeated use of filler year after year, excessive filler water content, and infection of fungal material by miscellaneous fungi. The main pest of Gastrodia elata is the false leaf beetle, which can be captured and killed or controlled with chemicals.

5. Harvesting Gastrodia elata has a relatively long growth period and is generally harvested in late autumn and early winter. At harvest, separate the various types of Gastrodia elata. Except for arrow Gastrodia kept for seed, the rest is processed or used as medicinal material. Generally, small white Gastrodia is suitable as seed Gastrodia. Seed Gastrodia not planted immediately should have the tail vegetative propagation stem removed, be air-dried for 1 to 2 days, and stored in a wooden box. The storage method is as follows: spread one layer of seed Gastrodia, then cover with one layer of yellow sand, then place another layer of seed Gastrodia, and in this way place 4 to 5 layers in total. The wooden box should be placed on the ground where the winter low temperature reaches 4°C. After dormancy, Gastrodia elata has strong growth ability, so inspect frequently. If the surface 3 to 5 cm of sand is dry, spray an appropriate amount of water to prevent Gastrodia elata from shrinking. Watering should be little and even; too much or too frequent watering will cause Gastrodia elata to rot. Generally, seed Gastrodia stored on the ground generally germinates in early April, so storing on the ground for 45 to 60 days is more favorable for the growth of Gastrodia elata.