What are the growing environment requirements for Gastrodia elata (tianma)

Gastrodia elata prefers a cool and humid environment, is cold-tolerant, and fears high temperatures. Gastrodia elata has no roots and no chlorophyll to absorb and produce nutrients, so it must rely on Armillaria mellea to provide them. Armillaria mellea is a facultative fungus that often parasitizes or saprophytically lives in the tissues of tree roots and old trees. It begins to grow at 6-8°C, can grow normally at 60%-80% soil moisture and 20°C, with the optimum growth temperature being 20-26°C; growth slows above 28°C and stops above 32°C. Gastrodia elata and Armillaria mellea have a nutritional symbiotic relationship. The rhizomorphs of Armillaria mellea invade the epidermal tissue of the Gastrodia elata tuber; the tips of the rhizomorphs rupture, and the hyphae invade the parenchyma cells of the cortex, decomposing and absorbing the epidermal cells. The hyphae continue to extend inward, and are then decomposed and absorbed by the digestive layer cells of Gastrodia elata, supplying nutrients for its growth.

Gastrodia elata grows best at 20-25°C, and growth is inhibited above 30°C. In spring, when the ground temperature at 15 cm reaches above 10°C, the buds of Gastrodia elata begin to sprout and start propagating daughter tubers. It grows rapidly from June to July, slows in September, and enters dormancy in late October when the ground temperature drops below 10°C. It takes 4-5 years from seed to flowering.

Gastrodia elata seeds have no endosperm, and the embryo is undifferentiated, so they cannot provide a nutritional source for germination on their own. Under natural conditions, seed germination requires the participation of fungi in addition to the conditions needed by ordinary green plants. Under natural conditions, seeds begin to germinate in early May at 10-20°C, but the germination rate is extremely low, generally 1%-10%. If newly harvested seeds are stored under low temperature (5°C) dry and sealed storage conditions for 180 days, a 50% germination rate can still be maintained.