What are the methods for rapidly growing seedlings of Japanese euonymus (Euonymus japonicus)?
1. Propagation: Cuttings are the main method.
(1) Cutting time
The traditional cutting time in the north is mostly from late October to early November, that is, dormant-season cuttings. Because the cutting season is late and the temperature is low, roots cannot form in the same year, and transplanting must wait until roots form the following spring. The transplanting time is accordingly delayed, resulting in a short growth period and small growth increment in the year of transplanting. The seedlings can only reach the out-planting standard in spring or autumn of the fourth year in the nursery, meaning it takes two and a half to three years from cutting propagation to out-planting.
To achieve rapid seedling production and shorten the nursery cycle, we changed the cutting time to the growing season, from May to early October. Cuttings made from May to August can be transplanted in the same year; cuttings made from August to early October can be transplanted early the following spring after the soil thaws, extending the growth period in the year of transplanting. The seedlings have a large growth increment, laying the foundation for rapid seedling formation. In short, the practice of early cutting, early transplanting, and early out-planting shortens the time required compared with traditional dormant-season cutting propagation by half a year to one and a half years. The whole process of growing-season cutting propagation takes about one and a half to two years. In addition, because propagation can be carried out in batches from May to early October, the tight supply and demand of seedlings is alleviated, and year-round supply of seedlings can basically be ensured.
(2) Cutting process. Lay out a seedbed in a high, dry area, 1.2 m-1.5 m wide, with length depending on the site and the number of seedlings needed. After leveling and removing debris, spread clean river sand about 20 cm thick on top, and spray the sand bed thoroughly with a 0.3% potassium permanganate solution for disinfection. Cuttings used for growing-season propagation should be robust, free of pests and diseases, and at least semi-lignified. Cut them into 10 cm to 15 cm lengths, remove the middle and lower leaves, and keep the robust mature leaves in the middle and upper parts. Soak the base of the trimmed cuttings in a 100 mg/kg indolebutyric acid solution for 4-6 hours, or dip them quickly in a 500 mg/kg indolebutyric acid solution to promote rooting. Use a thin bamboo stick or steel bar to make holes in the prepared sand bed at a spacing of 4-5 cm between plants and rows, then insert the treated cuttings into the holes to a depth of 1/2-1/3 of the cutting length. Press the sand around the cuttings firmly by hand so that the two are in close contact, facilitating later water uptake. After cutting, water or spray the sand bed thoroughly, cover it with a plastic-film arched shed, and shade the film above with bamboo blinds, reed blinds, shade netting, or similar materials.
(3) Management after cutting. After cutting, maintain the air humidity inside the arched shed at about 80%-90%. The sand moisture should be such that it forms a ball when squeezed in the hand and breaks apart at a touch, with a water content of about 60-80%. Keep the temperature below 35°C, with 25-30°C being suitable. The microclimate inside the shed can be regulated by spraying water (directly outside the film is acceptable), watering, covering the film, shading, and ventilation. After about 30-40 days, once the cuttings have rooted relatively completely and fully, gradually ventilate and remove the shading materials to harden the seedlings. After about 7-10 days, the seedlings can be transplanted.
2. Transplanting: It is best to transplant on cloudy days or before rainy days. Seedlings that have not undergone long-term storage and transport can be transplanted bare-rooted without soil balls; small seedlings can be planted bare-rooted, while large seedlings need soil balls. Transplant at a density of 20 x 25 cm. After planting, the soil must be pressed firm, and water thoroughly immediately after transplanting. The second and third waterings are crucial to seedling survival, especially when transplanting in the high-temperature summer season. Depending on the weather and soil moisture, the second watering can be done within 3-7 days after the first watering. Potted plants should temporarily be placed in a semi-shaded spot. Keep the soil moist during the growing season and fertilize once every 2 months. Shape the plant through pruning. Stop fertilizing in winter.
3. Key cultivation points during the seedling growth period: To achieve rapid seedling formation, after the transplanted seedlings survive, management of fertilizer, water, pruning, and other aspects should also be strengthened.
(1) Fertilizer and water: When transplanting seedlings, apply an appropriate amount of decomposed organic fertilizer in combination with soil preparation. If conditions do not allow, apply crushed straw. Apply about 7 kg of urea per 666.7 sq m. During the growing season, 5 kg of urea, 3-5 kg of monopotassium phosphate, etc. can be applied as topdressing. Fertilization should be combined with watering. Note that after September, control heavy watering and stop applying nitrogen fertilizer to promote full and robust seedlings and prevent late-season excessive vegetative growth, which can cause branch dieback in winter and spring. Before the soil freezes, water thoroughly with antifreeze water to prepare for overwintering. Before spring budbreak, water thoroughly with budbreak water to facilitate spring shoot growth. In addition, to benefit seedling growth, the soil can be managed with mulching for water-saving and drought-resistant cultivation. Mulching materials include wheat straw, sawdust, spent mushroom substrate, etc. The mulching thickness is about 15-20 cm. This method is very beneficial for saving water and building soil fertility, and can be carried out throughout the year. In short, fertilizer and water management during the seedling growth period should follow the principle of promoting early and controlling late.
(2) Pruning: Commercial seedlings are required to have a certain height, generally more than 60 cm, as well as a certain number of branches and a certain crown width. Generally, for use as a hedge, each plant is required to have 5-7 relatively long branches. Therefore, reasonable shaping and pruning during the seedling stage must be strengthened. After transplanting, if the seedlings grow rapidly, pinch the growing tips of plants with fewer than 4 branches to promote lateral buds to sprout into long branches; for branches that grow too long and too vigorously in spring and summer, remove the tips and pinch them at any time to balance the growth vigor of the whole plant's branches; after entering autumn in September, pinch the tips of all branches that have not yet set terminal buds and stopped growing, to control elongation growth, promote branch fullness, and raise the nutritional accumulation level of the whole plant, which is beneficial for overwintering and freeze protection and for budding, shoot growth, and leaf expansion the following spring; before growth begins in spring, shorten plants whose long branches are fewer than 4, to stimulate lateral buds to sprout and grow into long branches.
(3) Application of growth regulators: From mid-August to mid-October, spray a 600-1000 mg/kg paclobutrazol solution once a month, which can effectively control the elongation growth of new shoots and make the branches robust and full. In addition, soil application can also achieve the same effect. In August-September, apply evenly at a rate of 500-600 g per 666.7 sq m into a soil layer about 20 cm deep, and water once after application so that the seedling roots can absorb it.