Detailed Explanation of the Production Technology for Sexual Propagation of Gastrodia elata

In recent years, in the Gastrodia elata production of our county, we have adopted the direct seeding sexual propagation technology of Gastrodia elata seeds to replace the previous vegetative propagation cultivation method. This not only saves labor and time, increases yield, and raises farmers' income, but also reduces the amount of timber harvested, which is beneficial to water and soil conservation in the Tongbai Mountain area at the source of the Huai River. It has achieved dual benefits and alleviated the conflict between mushroom cultivation and forestry. Because the sexual propagation technology of Gastrodia elata uses branches with a stem diameter of 3-6 cm, small wood, and broadleaf litter, each 0.5 sq m cultivation pit can obtain about 4 kg of seed tubers in the same year, and about 20 kg of finished arrow tubers per pit in the winter of the following year, with a benefit of about 400 yuan per pit, showing significant economic benefits.

I. Selection, Retention, and Storage of Seed Tubers

In wild areas or artificial cultivation sites, select and retain arrow tubers with plump terminal arrow buds, fresh, robust, free of wounds, free of pests and diseases, and weighing about 200 g. After spreading to cool and allowing some surface moisture to be lost, store them for spring planting. The storage location can be indoors or outdoors; the key is to prevent freezing damage. The medium-grained sand used for burying arrow tubers should have a moisture content of about 20%, preferably dry rather than wet, to prevent the seed tubers from rotting. For outdoor storage, choose a site with good drainage, loose soil, and shelter from wind and facing the sun; for indoor storage, ventilation must be good. The size of the burying pit can be determined by the storage quantity. Generally, outdoors, a strip-shaped small pit 35 cm deep is suitable; indoors, a sandbox can be used for storage. When storing, spread a layer of about 10 cm of coarse sand mixed with coal cinders at the bottom of the pit, then spread a layer of medium-grained sand on top. On the sand layer, place arrow tubers at a spacing of 5 cm. After one layer is full, cover with sand and place a second layer. In this way, 2-3 layers can be placed, then cover with 10 cm of fine sandy soil, and cover the surface with rice, wheat straw, or other crop straw to protect against cold and keep warm. Regularly check the moisture content of the covering material and adjust it promptly to ensure the quality of the seed tubers.

II. Cultivation and Management of Arrow Tubers

Using a greenhouse or arched shed to cultivate seed tubers is currently a relatively practical method. Greenhouses and arched sheds can be built similarly to those used for vegetables, and the size can be determined according to the scale of breeding. If a household conducts a small amount of breeding, about 20 d before the natural emergence season of local arrowhead, a small arched shed with a ground pool can be used for breeding. However, regardless of the method used for breeding, a site with high terrain, shelter from wind and facing the sun, and capable of ventilation must be selected. Using a shed or greenhouse to cultivate seed tubers can advance maturity by more than one month, which is conducive to early sowing (early May) and high yield, shortening the tuber formation cycle. Arrowhead cultivation mostly adopts the box-type cultivation method. When planting, spread about 15 cm of coarse sand mixed with coal cinders at the bottom of the box, then spread medium-grained sand on the mixed layer. On the medium sand layer, plant arrowhead in a triangular arrangement, with a spacing of more than 10 cm. During operation, do not damage the tuber skin or arrow buds, otherwise the seed tubers are very likely to rot. After cultivation, cover the surface with about 8 cm of fine sand or sandy loam. After planting arrowhead, management can start from the following aspects:

(1) Shading. The flower scape of Gastrodia elata is most averse to direct sunlight; direct light will cause the scape to turn black and lodge. The best shading method is to stretch a layer of black shade net with a shading rate of 60% under the plastic film of the shed. For a small amount of breeding, other materials can be used to create a shading effect of four parts light and six parts shade.

(2) Moisture retention. During the high-temperature period from April to July, when Gastrodia elata bolts, flowers, and fruits, the moisture in the culture substrate is lost relatively heavily. The culture material must be replenished with water in time to keep the substrate moist but not waterlogged.

(3) Topping. The terminal inflorescence of Gastrodia elata has a low probability of setting fruit. After the bud stage ends, remove the terminal "flower bud cluster." This can not only reduce nutrient loss but also make the capsules of the whole plant plump and ensure seed quality.

(4) Lodging prevention. The flower scape of Gastrodia elata is hollow. Generally, for a 200 g arrow tuber, the scape height is about 1 m. If exposed to wind or if the fruit spike is too heavy, it is very likely to break. Therefore, inserting stakes to support the scape is very important.

III. Artificial Pollination Technology

Because the flower structure of Gastrodia elata is special, the anther is covered by the anther cap, the cap does not fall off by itself, and the anther is sticky and clumped and does not disperse by itself. Especially in greenhouse or arched shed breeding, there are few pollinating insects active, so artificial pollination must be carried out. After the inflorescence of Gastrodia elata begins to flower, artificial pollination must be carried out every day. To ensure the success rate of pollination, follow the principle of pollinating each flower as it opens. The best pollination time is from 9:00 to 12:00 in the morning, and pollination should be completed no later than the morning of the next day. When pollinating, gently pinch the ovary with one hand, press down the lip with a bamboo stick with the other hand, then pick out the anther mass and place it accurately on the smooth stigma. Pollination within the same flower, between different flowers, or between different plants is all acceptable. Cross-pollination has strong hybrid vigor and high yield. As long as artificial pollination is carried out according to the procedures, the success rate is generally above 90%.

Gastrodia elata seeds mature from bottom to top. When gently pinched by hand, if the seeds are soft and the longitudinal dehiscence line of the seed coat is about to split, it indicates that the upper capsules have also matured and should be harvested in time for use. It is best to sow seeds immediately after harvest, and at the latest, sowing should be completed 3-4 d before the longitudinal dehiscence line splits. If they cannot all be sown at once, it is best to store them in a refrigerator at about 4°C. Never expose the capsules to the sun. The seeds in mature capsules are soft and easy to shake out, light grayish-yellow in color, and the period before the fruit splits is the best sowing time. If too early, the seeds are white and immature and will not scatter; if too late, the seeds are brownish-yellow and have lost germination capacity. If the seeds are first sown in germination fungus and placed in a plastic bag, the time for hole sowing can be extended.

IV. Pre-planting Preparation

For each pit, prepare 7-14 chestnut-type or other broadleaf tree branches or wood segments with a stem diameter of 3-6 cm and a length of 70 cm. After cutting, soak them in 0.25% ammonium nitrate for 24 h, and cut fish-scale notches on the wood segments at intervals of 15 cm for later use. Each pit needs 200 kg of clean, uncontaminated river sand; medium-coarse sand is best. Rinse the river sand with clean water 2 h before use. Each pit uses 2 kg of chestnut-type fallen leaves from the previous year; soak them in clean water for 4 h before use, drain off excess water, and set aside. Each pit uses 3 kg of small wood segments with a stem diameter of 1.5 cm and a length of 4-6 cm. In addition, each pit needs 1-2 bottles each of high-quality Armillaria mellea and germination fungus, and 8-16 seed capsules (about 16 for a double layer).

A key task before sowing is to thoroughly mix the germination fungus with Gastrodia elata seeds. During operation, first cut the leaf culture medium of the germination fungus into small pieces about 1.5 cm square with a sharp knife, then place them in a clean basin. With the right hand, gently pinch the capsule so that the longitudinal dehiscence line splits, shake the Gastrodia elata seeds onto the germination fungus in the basin, then mix with both hands. After shaking each capsule, mix once, and crush the pericarp and scatter it into the germination fungus. This work should be carried out in a windless environment to prevent the tiny seeds from being blown away by the wind.

V. Sowing Technology

The sowing pit can be enclosed with small tree trunks, wooden boards, or bricks into a box pool 90 cm square. For large-scale cultivation, molds can be made. First, spread 10 cm of coarse gravel at the bottom of the pit, then spread 10 cm of river sand, scatter a layer of soaked fallen leaves and pat them flat, then evenly scatter the germination fungus leaf fragments mixed with Gastrodia elata seeds on the leaf layer. On this sowing layer, place 7 wood segments, then place Armillaria mellea spawn at the fish-scale notches and at both ends of the wood segments, and place small wood knots diagonally between the sticks to guide Armillaria mellea onto the sticks. After completing the above steps, gently cover with river sand about 5 cm thick, then sow the second layer in the same way (single-layer sowing is also possible), and finally cover the top layer with 20 cm of river sand and pat it flat.

VI. Post-sowing Management

After sowing in the Gastrodia elata pit, first carry out shading protection. A shade net with a shading rate of 80% can be used to cover the top layer and surroundings, or branches and leaves can be used for covering and enclosing, creating a cool environment for the pit to facilitate the growth of Armillaria mellea and safe overwintering. According to test measurements, outdoors with good shading, the temperature between the Gastrodia elata pit and the ground surface generally does not exceed 30°C in summer; indoors with good ventilation, the temperature between the pit and the ground surface does not exceed 26°C. The second issue is moisture retention. After inoculation, the moisture content of the sand base is about 55%, which is favorable for the growth of both fungi and seed tubers. In practice, about one week after sowing, water can be sprayed on the bricks, wooden boards, and walkways around the pit, and a small amount of water can also be sprayed on the sand layer on the pit surface. After one month, the sand layer on the pit surface can be heavily watered. At the same time, the cultivation site must be well ventilated. Especially for indoor cultivation, regular ventilation is necessary, which will play a good regulatory role in preventing infection of the fungal wood, promoting germination and growth of seed tubers, and lowering temperature in summer.

Using Gastrodia elata seeds for sexual propagation production, as long as scientific management is carried out, those sown before early June can grow into white-headed arrow tubers in the same year, and the arrow tuber formation cycle is only one and a half years. It is indeed a short, flat, and fast new project for becoming wealthy.