What temperature conditions does Gastrodia elata need to grow?
Q: What kind of temperature conditions does Gastrodia elata need to grow? What are the extreme temperatures?
A: This question seems simple, but is actually rather complex. Based on the actual situation in our province, we might as well give a brief explanation from the following two aspects.
First, the original intention of most farmer friends in asking this question should refer to the adaptability of Gastrodia elata tubers to temperature in asexual cultivation. As a plant, Gastrodia elata has no roots and no leaves, and its ability to adapt to and regulate temperature is weak, which is its growth disadvantage. However, since Gastrodia elata spends its entire life in an underground environment (except for sexual seeds), its tubers can grow normally by relying on the stable temperature conditions in the soil. The temperature we refer to here is the temperature of the underground soil layer where Gastrodia elata is located, not the air temperature. Generally speaking, when the ground temperature reaches above 12°C, the cells of Gastrodia elata begin to become active and can begin to digest and absorb Armillaria mellea as their own food to supply their own growth and enlargement. As the temperature rises, their vitality increases, reaching its peak under conditions of 20-25°C, just like the youth period of humans, when life is very active and healthy. But when the temperature continues to rise above 30°C, biological metabolism stops, and the ability to resist adverse external conditions is lost.
According to our experimental statistical data, from the tiny young mi-ma to growing into jian-ma, Gastrodia elata requires an effective accumulated temperature of about 3800°C, and at around 4000°C, its commercial quality is even better. Calculated on a one-year growth cycle, an average daily temperature between 10-12°C is most suitable; therefore, under general natural conditions, unprotected cultivation can be carried out in all parts of Shandong. If it is in areas south of the Yangtze River, then the issue of cooling in summer needs to be properly considered; for example, in woodlands, orchards, hillsides and other places, the effect is very good; and for example, in Northeast China, the frozen thickness of the soil layer in winter can reach 30 cm or even more, so the issues of heat preservation and temperature increase should be considered, such as thickening the coverage of grass and leaves, or using plastic shed facilities, etc., which can effectively solve the problem. As long as the soil layer temperature where Gastrodia elata is located is higher than minus 4°C, it can overwinter normally, but if it is lower than minus 5°C, freezing damage will occur.
Second, the seeds of Gastrodia elata during sexual breeding have stricter requirements for temperature conditions. Because the sexual seeds of Gastrodia elata are as small as dust, their ability to adapt to and resist external conditions is very poor; therefore, this has also become one of the difficulties in the sexual breeding of Gastrodia elata. Under general conditions, Gastrodia elata seeds can germinate at 20-28°C, and can even germinate under 15°C conditions, but when the temperature drops below 13°C, there is no possibility of germination. When the temperature rises to 30°C, the seeds are not easy to germinate. We have conducted special research on this: 13-15°C, germination rate 13%; 17-19°C, germination rate 43%; 20-22°C, germination rate 76%; 23-25°C, germination rate 78%; 26-28°C, germination rate 81%; 29-31°C, germination rate 37%; after 33°C, the germination rate is close to zero.
In addition, during the sexual breeding stage, the germination and bolting of jian-ma, the growth of flower stems, pollen formation, pollination, and until seed maturation all require certain temperature conditions. Due to space limitations, they will not be described in detail.