The survival principle of stratified seedlings is that branches get nutrients from the mother body under long-term suitable water, temperature and gas conditions, so as to take root from the root primordia and survive. For some tree species with difficulty in rooting, the epidermis of the branches buried in the soil can also be cut to promote the formation of callus and further rooting, so that the branches in the soil can gradually take root, which can form seedlings more quickly. Some tree species that are difficult to survive by cutting can achieve good results through layering, but the disadvantage is low reproduction rate.
(a) layered method:
Various forms of stratification
1. Piling batten 2. Ordinary battens 3. Corrugated slats 4. Horizontal slats 5. Air slats.
1. Low pressure method:
It can also be divided into pile-soil layering and twig layering.
(1) Stacking layering: It is suitable for mother plants with many branches and trees with strong tillering ability. The mother tree can be planted in advance, and the plant spacing is1m×1.5m. After planting, the stubble should be leveled in the autumn of that year or the spring of the following year to promote the germination of new buds. From June to July, when the shoot height reaches 15 ~ 20cm, it should be buried with soil to make it take root and cut off from the mother plant to form seedlings that can live independently.
(2) Pressing branches: Before the trees begin to sprout in early spring, cut or girdle the elastic branches close to the ground where they are ready to take root, then press them into the opened ditch, cover them with 10 ~ 15 cm of soil, with the apex exposed from the ground, and tie them up with posts. After taking root, they will leave their mother's body and be independent. In addition, there are horizontal stratification, radial stratification and wavy stratification.
2. High pressure method:
For trees with hard wood, branches that are not easy to bend, or whose crowns are too high to withstand low pressure, high pressure method should be adopted. First, the epidermis is cut at the place where it is ready to take root, reaching the cambium, then the wound is filled with fertile and moist soil, and the outside is wrapped with plastic film or split bamboo tube, which is often kept moist, separated from the mother after taking root, and then cultivated into strong seedlings.
(2) Methods to promote layering to take root:
For plants that are not easy to take root or take root for a long time, technical treatment can be taken to promote rooting. Specific methods include: scribing method, cutting method, binding method, twisting method, splitting method, softening method, growth stimulation method and soil improvement method.
All the above methods are aimed at blocking the downward transport of organic matter (carbohydrates, etc.). ), so that the upward transport of water and minerals is not affected, and nutrients are concentrated in the treatment site, which is beneficial to the formation of adventitious roots. At the same time, it also stimulates the production of auxin.
(3) After hierarchical management:
After stratification, the soil should be kept properly moist, and grass should be covered in cold areas in winter to avoid freezing injury. Check whether the layering in the soil is exposed to the ground at any time. If it is exposed, it should be weighed. If the branches left on the ground grow too long, you can cut off the top appropriately. In a word, according to the biological characteristics of different tree species, appropriate layering methods should be adopted at appropriate periods, and conditions such as humidity, ventilation and suitable temperature should be kept constantly during the growth period (especially in the early stage), so as to take root well and successfully grow seedlings.
The time of separating layered seedlings is based on the growth of roots. If you have a good root system, you can leave the mother tree. For larger branches, pruning at one time is not allowed, but should be divided into 2 ~ 3 times. Newly separated plants should be watered for shade, and plants that are afraid of cold should be moved into greenhouses for wintering.
The layering method is simpler than the cutting method. However, the layering propagation efficiency is low, it is difficult to produce a large number of seedlings at one time, and the cost is high, which is not suitable for large-scale operation.