Detailed Explanation of the Key Technical Points for the Four-in-Pit Companion Planting Method of Gastrodia elata

The sexual reproduction four-in-pit companion planting method for Gastrodia elata involves placing Gastrodia elata seeds, germination-promoting fungi, Armillaria mellea spawn, and fungal wood together into a pit for companion planting, which is called the four-in-pit companion planting method. This companion planting method saves labor, saves time, increases Gastrodia elata yield, and also saves wood, yielding double benefits, and is worth promoting.

1. Selection, Retention and Storage of Seed Tubers

Select and retain arrow tubers with plump top arrow buds, fresh, free of injuries, free of pests and diseases, and weighing about 200 g; after spreading them out to air-dry and drying the surface moisture, store them for use in spring planting. Both indoor and outdoor storage are acceptable; the key is to prevent freezing injury and rot. The medium-grained river sand used for burying arrow tubers should have a moisture content of 20%; it is better to keep it dry than wet, in order to prevent the seed tubers from rotting. For outdoor storage, choose a site with good drainage, loose soil, and shelter from the wind while facing the sun. For indoor storage, there must be good ventilation. The size of the burial site can be determined according to the storage quantity. Generally, outdoors a strip-shaped small pit 35 cm deep is suitable, while indoors a wooden box with sand storage can be used. When storing, first spread a 10 cm thick layer of coarse sand or a coal cinder mixture on the bottom of the box, then spread a layer of medium-grained sand on top, and place 1 arrow tuber on the sand layer at a spacing of 2 cm. After one layer is full, cover with 5 cm of sand, then place the second layer, and in this way 2-3 layers can be placed. After that, cover with 10 cm of fine sand, and then cover the surface with rice, wheat, or other crop straw to prevent cold and keep warm. Regularly check the moisture content of the covering material and adjust the humidity well to ensure the quality of the seed tubers.

2. Cultivation of Arrow Tubers

Using a greenhouse or arched shed to cultivate arrow tubers for breeding can advance maturity by more than 1 month, which is conducive to early sowing (in June) and can shorten the tuber formation cycle. Greenhouses and arched sheds can be built by imitating the construction methods of vegetable greenhouses, and the size can be determined according to the scale of cultivation. If a single household carries out a small amount of cultivation, box cultivation can be done in the natural season and then placed in a greenhouse or arched shed for cultivation. However, no matter which method is used for cultivation, a site with high terrain, shelter from wind, facing the sun, and good ventilation should be selected.

For example, in the box cultivation method for arrow tubers, first spread a 10 cm thick layer of coarse sand or coal cinder mixture (also called culture material or culture substrate) on the bottom of the box, then plant arrow tubers on the sand layer in a triangular arrangement, with a spacing of 10 cm between arrow tubers. During operation, do not bruise the tuber skin or arrow buds, otherwise the seed tubers are very likely to rot. After planting, cover the surface with 8 cm of fine sand and place it in a greenhouse or arched shed for management and breeding.

3. Management After Arrow Tuber Cultivation

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

2. Moisture retention Gastrodia elata bolting, flowering, and capsule formation occur in May-June, when the moisture in the culture substrate is lost relatively greatly, so the culture material must be replenished with water in time, keeping the substrate moist but not waterlogged.

3. Topping The top inflorescence of Gastrodia elata has a low probability of setting fruit, so after budding ends, the top "inflorescence tip" should be removed, which can both reduce nutrient loss and make the capsules of the whole plant plump, ensuring seed quality.

4. Lodging prevention The flower scape of Gastrodia elata is hollow. Generally, for an arrow tuber weighing 200 g, the scape height is about 1 m. If exposed to wind or if the fruit spike is too heavy, breakage is very likely to occur, so inserting stakes to support the scape is very important.

4. Artificial Pollination

Because the flower structure of Gastrodia elata is special, the anther (that is, pollen) is covered by the anther cap, and the anther cap does not fall off by itself. The anther is sticky and clumps together, so it is not released by itself. Especially when cultivated for breeding in a greenhouse or arched shed, there is very little insect activity for transmission, so artificial pollination must be carried out. When carrying out artificial pollination on Gastrodia elata, in order to ensure the success rate of pollination, the principle of pollinating each flower as it opens should be followed. The best pollination time is from 10 a.m. to 2 p.m. When pollinating, lightly pinch the ovary with one hand, press down the labellum 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, the same plant, or between different flowers and different plants is all acceptable. Cross-pollination between different flowers has strong hybrid vigor and high yield. As long as artificial pollination is carried out according to the procedures, the pollination success rate is generally above 90%.

Gastrodia elata seeds mature from bottom to top. When lightly pinched by hand, the seeds are soft and the longitudinal dehiscence line of the seed coat is about to split, indicating that the several capsules above it have also matured and should be harvested in time for later use. It is best to sow the seeds immediately after harvesting; at the latest, sowing should be completed 3-4 days before the longitudinal dehiscence line splits. If they cannot all be sown for the time being, it is best to store them in a refrigerator at about 4 degrees C. Exposing the capsules to the sun is strictly prohibited. The seeds in mature capsules are loose and easily scattered, and light grayish-yellow in color. Before the fruit splits is the best sowing period. If too early, the seeds are white, immature, and will not scatter; if too late, the seeds are brownish-yellow and have already lost their germination rate. If the seeds are first sown in germination-promoting fungi and placed in a plastic bag, the sowing time can be extended.

5. Preparation Before Sowing

For each square meter, prepare 30 kg of fresh oak (chestnut oak) wooden sticks with a diameter of 3-10 cm and a length of 60 cm, soak them in a 0.25% ammonium nitrate solution for 6-12 hours, and cut fish-scale notches on the wooden sticks at intervals of 3-7 cm, cutting 3 sides in total. Each square meter requires 400 kg of clean, uncontaminated medium-coarse river sand. It is best to rinse the river sand once with clean water 6 hours before use. Each square meter uses 1 kg of oak fallen leaves; before use, soak them in clean water for 4 hours and drain off excess water for later use. Each square meter uses 3 kg of oak branches with a diameter of 1.5 cm and a length of 6 cm. In addition, each square meter requires 4 bottles of high-quality Armillaria mellea spawn, 2 bottles (or 2 bags) of germination-promoting fungi, and 16-20 Gastrodia elata capsules.

A key task before sowing is thoroughly mixing the germination-promoting fungi with Gastrodia elata seeds. During operation, first cut the germination-promoting fungi into small pieces about 1.5 cm square with a sharp knife, then put them into a clean basin, lightly pinch the capsules by hand so that the longitudinal dehiscence line splits, and shake the Gastrodia elata seeds into the basin onto the germination-promoting fungi