Detailed Explanation of Key Techniques for Authentic Cave Cultivation of Gastrodia elata
Gastrodia elata, also called red arrow, wind-stilling grass, and water potato, is a perennial herb of the genus Gastrodia in the Orchidaceae family. It is a valuable medicinal material for treating diseases of the nervous system. 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, boosting qi and stopping convulsions, nourishing the liver, and relieving spasms. Artificially cave-cultivated Gastrodia elata shows no obvious difference from wild Gastrodia elata in morphology or efficacy, so developing artificial cultivation of Gastrodia elata is an effective measure to address the dwindling supply of wild Gastrodia elata. Caves (or cellars) 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. Cave cultivation of Gastrodia elata has high yield, simple technology, low labor input, low cost, and easy management, and can avoid to a large extent harm from humans, livestock, diseases, and pests.
Because Gastrodia elata cannot nourish itself, its growth must rely on Armillaria mellea to supply basic nutrients. 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 cave. A cave for cultivating Gastrodia elata should have the following conditions: (1) The cave should have a low-temperature period of more than one month in winter with temperatures above 10°C; (2) The summer temperature should not exceed 28°C, to facilitate summer growth of Gastrodia elata; (3) Both ends of the cave should have closable openings to help regulate temperature and humidity inside the cave. Generally, shallow caves are preferable. Before cultivation, clean and level the cave, dig small water ditches along both walls, and preferably whitewash the inner walls and fumigate them with sulfur or formaldehyde for sterilization.
2. Cultivation time. The sowing period is January to February, when the cave 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 sprout while Armillaria mellea has already grown well and has established a symbiotic relationship with Gastrodia elata.
3. Cultivating seedling material. Build a fungal wood cellar 2 to 3 months before planting Gastrodia elata. The method is as follows: Lay bricks or cobblestones on the ground floor, 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 length determined by the amount of fungal wood. There is no need to cement the upper and lower bricks together, and leave 1 cm gaps between the left and right bricks. The filling material is a mixture of rice husks and yellow sand (volume ratio 1:1) with a moisture content of about 30%. First spread 6 cm of filling material, then lay 80 cm segments of new wood cut with fish-scale notches and with a moisture content of 40%. Place several pieces of inoculated fungal wood beside the new wood segments and fill the gaps with filling material. 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 filling material with a moisture content of about 50%. Check the moisture content of the filling material every 3 to 5 days. If the moisture content is insufficient, sprinkle water to maintain it. Usually pay attention to loosening the soil and ventilating it to favor the growth of fungal strands. Well-cultivated fungal wood will have large numbers of fungal strands protruding from the surface.
4. Cultivating Gastrodia elata. In caves, brick heap cellars are generally the most practical for cultivation. The construction method of the heap cellar is the same as that of the fungal wood cellar. Spread a 6 cm thick mixed filling material of sawdust (or rice husks) and sand (volume ratio 1:1) on the bottom of the cellar, and place fungal wood in rows with 3 to 4 cm between pieces. Fill the gaps with filling material so that the fungal wood is half buried. Place one seed Gastrodia elata at both ends of each piece of fungal wood and at each fish-scale notch. Place covering material directly above the fungal wood. The thickness should be such that the fungal wood is shallowly buried. In this way, 2 to 3 layers can be laid in total, with sufficient water applied to each layer, and finally cover with 12 cm of covering material and water thoroughly, with the moisture content such that the surface does not dry out.
Cave planting of Gastrodia elata can use sexual reproduction. New seeds of Gastrodia elata can be scattered on the fungal wood, 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 wood. The seed Gastrodia density is 300 g/sq m. Usually the upper layers produce more arrow Gastrodia, and the lower layers produce more white Gastrodia.
Because the cave 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 over the rice husk and river sand material, and water can be added with a watering can. From August to October the cave is damp; this can be regulated by using a fan to increase ventilation and air exchange.
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 moisture content of the filling material should be controlled at about 25%. Too high a moisture content will affect the growth of Armillaria mellea and cause the seed Gastrodia to rot. In the middle stage, because Gastrodia elata sprouts and grows rapidly, water demand gradually increases. At this time the moisture content of the filling material should reach about 50%, and watering should be light and frequent. If the filling material becomes compacted after watering, loosen the soil promptly. After arrow Gastrodia forms, humidity should be reduced to prevent rot.
The causes of Gastrodia elata rot include: continuous use of filling material year after year, excessive moisture content in the filling material, and infection of the fungal wood by miscellaneous fungi. The main insect pest of Gastrodia elata is the false leaf beetle, which can be caught and killed or controlled with pesticides.
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 those kept for seed, the rest of the arrow Gastrodia is processed or used as medicinal material. Generally, small white Gastrodia is suitable for use as seed Gastrodia. Seed Gastrodia not planted immediately should have the tail-end 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. The wooden box should be placed on the ground where the winter low temperature reaches 4°C. After dormancy, Gastrodia elata has strong growth capacity, so inspect frequently. If the top 3 to 5 cm of sand has dried, spray an appropriate amount of water to prevent the 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 sprouts universally in early April, so storing on the ground for 45 to 60 days is more favorable for the growth of Gastrodia elata.