Climatic environment requirements for Gastrodia elata cultivation

Gastrodia elata, also known as chijian, dingfengcao, shuiyangyu, etc., is a precious medicinal material renowned both in China and abroad, known as the "king of medicinal materials," with extremely high medical and health value. What people commonly refer to as Gastrodia elata is its dried tuber. In terms of plant taxonomy, Gastrodia elata belongs to the Orchidaceae family as a perennial herbaceous plant, but it differs from the green plants we commonly refer to: its plant body is a single fleshy shoot, yellow-red in color, with no roots and no green leaves, and it cannot perform photosynthesis. Throughout its entire growth and development period, it must live in "symbiosis" with a type of fungus called "Armillaria mellea," relying on lytic enzymes it produces itself to dissolve the Armillaria mellea hyphae, thereby obtaining water and nutrients from Armillaria mellea to sustain its own growth.

As a precious Chinese medicinal material, when people cultivate Gastrodia elata, they must not only pursue yield but also pay attention to quality, that is, fully ensuring the content of active ingredients; otherwise, it may be a case of "though the substance is not counterfeit, the variety differs, and the medicinal properties differ." Only under specific environmental conditions can Chinese medicinal materials with specific medicinal properties and efficacy be produced. The famous words of Yan Ying from the Spring and Autumn period, "Oranges grown south of the Huai River are oranges; grown north of the Huai River they are trifoliate oranges," vividly illustrate the importance of environmental conditions, especially climatic conditions, to the production of Chinese medicinal materials. Zhishi (trifoliate orange fruit) and jupi (orange peel) are two commonly used Chinese medicinal materials, yet their primary indications and effects differ markedly.

China has complex terrain and diverse climate types, and especially in the vast mountainous areas, suitable regions for Gastrodia elata cultivation may exist. To cultivate Gastrodia elata artificially, one must understand the requirements of Gastrodia elata growth for environmental conditions. Only by selecting or creating a microclimate environment suitable for Gastrodia elata growth according to local conditions, and by using agricultural technical measures to fully meet the needs of Gastrodia elata growth, can high-quality Gastrodia elata be produced and relatively good economic benefits be obtained.

Temperature is the primary factor affecting Gastrodia elata growth. Gastrodia elata prefers to grow in an environment that is cool in summer and not overly cold in winter. It is relatively sensitive to temperature, and the level of temperature directly affects the growth, yield, and quality of Gastrodia elata. From the tiny mima to the mature jianma, Gastrodia elata requires an effective accumulated temperature of about 3800°C, and at around 4000°C, its commercial quality is even better. Generally speaking, when the ground temperature reaches above 12°C, Gastrodia elata cells begin to become active and can begin digesting and absorbing Armillaria mellea as nutrition for their own growth and enlargement; as the temperature rises, vitality increases. When the ground temperature reaches 20°C-25°C, this is the optimum temperature for the growth of Gastrodia elata and Armillaria mellea, and at this time Gastrodia elata grows and develops most rapidly. However, when the soil temperature continues to rise above 30°C, the growth of Armillaria mellea and Gastrodia elata is instead inhibited, and "aconite-shaped" jianma is easily produced. Therefore, in high-temperature seasons, attention should be paid to preventing heat and lowering temperature. When the air temperature is below 15°C, the growth rate of Gastrodia elata slows and gradually stalls as it enters overwintering dormancy. Gastrodia elata is relatively cold-tolerant; as long as the temperature of the soil layer in which it is located is above -4°C, it can overwinter normally, but if it is below -5°C, the Gastrodia elata tuber will suffer freeze damage and rot, affecting its safe overwintering.

Seed-used Gastrodia elata (abbreviated as seed corm) requires a certain period of low-temperature dormancy in winter before it can germinate normally the following spring. Under low-temperature conditions of 2°C-5°C, the seed corm needs about two months to pass through the dormancy period. If the low-temperature period is insufficient, even if germination conditions are suitable, the seed corm will not sprout. After the seed corm breaks dormancy, the speed of germination is also related to the low-temperature conditions received during dormancy: the longer the low-temperature treatment, the faster the germination speed; conversely, the slower it is.

Wild Gastrodia elata is generally distributed in areas with annual precipitation above 1000 mm, relative air humidity of about 80%, and soil moisture content of 50%-55%. Continuous overcast and rainy, wet and humid climatic conditions are most suitable for Gastrodia elata growth. Especially in the peak growth season from June to August, when nutrient accumulation in Gastrodia elata reaches its peak and more water is needed, abundant rainfall during this period is the key to ensuring a high yield of Gastrodia elata. By September, nutrient accumulation in Gastrodia elata enters its later stage and reaches the physiological maturity phase; at this time, soil moisture should be controlled below 40%. If there is excessive rain, Armillaria mellea grows vigorously, invades new Gastrodia elata, and decomposes Gastrodia elata tissue as nutrition, which will cause the Gastrodia elata tuber to rot, leading to reduced yield or lower quality.

Because Gastrodia elata is a non-green plant, from planting to harvest, the entire asexual reproduction process takes place underground, so light has no direct effect on the growth and reproduction of the underground tuber; it can only indirectly affect changes in soil temperature. If Gastrodia elata is cultivated in cool regions, increasing direct sunlight exposure can raise the ground temperature. After Gastrodia elata bolts and emerges from the soil (about two months), it needs a certain amount of scattered light, but strong light should be avoided. Intense direct light can cause sunscald, damage the Gastrodia elata stem, and easily lead to plant death. At the same time, direct sunlight increases soil water evaporation, lowers soil moisture, and affects tuber growth. Therefore, at this time, attention should be paid to building shade sheds to reduce direct sunlight exposure. Strong wind is harmful only to Gastrodia elata that has bolted and is flowering; it can break or blow down the flower stalk, affecting seed yield. Therefore, after emergence, the flower stalk should be protected from strong wind, such as by staking the emerged flower stalk.