Detailed Guide to Cultivation Techniques and Care Methods for Osmanthus Bonsai
Osmanthus is a famous fragrant flower, with leaves that stay emerald green all year round and a graceful, elegant tree form. When in full bloom, its branches are adorned with gold, with jade-green leaves and yellow flowers, and its rich fragrance fills the air, lasting for a long time and delighting the heart. It mostly blooms in autumn, hence its reputation for dominating the three autumn months and surpassing all other flowers. Four-season osmanthus blooms in all four seasons, offering an even longer ornamental period. There is also a kind of cold-dew osmanthus, which blooms in late autumn with a relatively late flowering period. The Tang dynasty poet Wang Wei wrote the line about cold dew moistening silently.
To make potted osmanthus bloom more and have fragrant scent, it is necessary to grasp important steps such as choosing good potting soil, watering at the right time, skillfully applying additional fertilizer, and proper pruning.
[Grafting Methods]
Bonsai osmanthus all use grafting methods, and stem grafting is the common form of grafting. Stem grafting includes cut grafting, cleft grafting and approach grafting. Commonly used rootstock species include small-leaf privet, Chinese privet and glossy privet. Cut grafting is more widely used. When grafting, cut off the rootstock at 5 cm above the ground, choose the side with smoother bark, cut vertically downward slightly into the wood, making an incision 2-3 cm deep. Take a mature one-year-old branch as the scion, 6-8 cm long, with 2-3 nodes.
Cut the lower end of the scion into a 2-3 cm slanted cut surface, and then cut the opposite side into a short cut surface of about 1 cm. Then press the long cut surface of the scion tightly against the cut surface of the rootstock, insert it into the incision, so that the cambium layers of the two cut surfaces are in close contact. Then wrap the bark layer of the rootstock incision around the outside of the scion, bind and fix it with plastic film tape, seal the rootstock incision and the top of the scion to prevent water evaporation, and it will easily survive.
Approach grafting is to cut away 5-10 cm from both the mother plant branch of the scion and the mother plant branch of the rootstock, to a depth reaching 1B3-1B2 of the trunk diameter into the xylem. Combine the two together, bind them well with plastic film tape, and separate each after they have survived. Approach grafting has a very reliable survival rate, and garden nurseries mostly use this method to cultivate potted four-season osmanthus.
[Potting Process]
Pot selection: Osmanthus has green leaves and yellow flowers and is evergreen all year round, so it is advisable to choose a relatively deep round pot or square pot. The diameter of the pot mouth should roughly match the spread of the osmanthus branches and leaves, which benefits root development and growth. For the pot material, purple clay ceramic pots or glazed ceramic pots are best. For color, purple or ochre is better, as it can form a sharp contrast with the colors of the flowers and leaves and increase the ornamental effect.
Soil: Osmanthus likes fertilizer, so it is advisable to use fertile, loose, well-drained sandy loam. The culture soil for potted osmanthus is usually made by mixing garden soil, composted manure and river sand in equal parts of 1B3 each. Attention must be paid to disinfection treatment so that it does not become infected with pests and diseases.
Planting: Osmanthus is suitable for planting in early spring or autumn. Before potting, place a layer of river sand or vermiculite at the bottom of the pot to facilitate aeration and drainage, and then spread a layer of peat soil or fine mud about 2-3 cm thick on top, reaching 1B3 of the pot depth. Then, put the osmanthus seedling with a root soil ball into the pot, fill with culture soil, press tightly with fingers, and fill soil until close to the pot rim. The soil surface should be 2-3 cm lower than the pot rim to facilitate watering and fertilizing. After planting, water thoroughly, then move it to a shaded place for about 10 days to let it “adapt to the pot” and gradually resume growth.
[Fertilizer and Water Management]
Because the volume of the flower pot is limited, potted osmanthus is prone to lacking nutrients and insufficient water, so it needs to be supplemented through fertilizing and watering. Additional fertilizer should be applied during the growing season. In the year of repotting, starting from June, combine with watering every 20 days or so and apply once a 15% fertilizer liquid soaked from decomposed pig manure and tung bran, or a liquid fertilizer soaked from 15% tung bran and compound fertilizer. Stop fertilizing in early October. The next year, after the plant grows new leaves, starting from April, apply the above liquid fertilizer at 15% once every 15 days; from June to August, increase the liquid fertilizer concentration to 20%-30%. If growth is robust, reduce the number of fertilizer applications and lower the fertilizer liquid concentration; from September to October, apply the above liquid fertilizer at 15% once every 20 days, and stop fertilizing after Frost's Descent.
After each fertilization, water at the right time according to the dryness and moisture of the potting soil. The number of waterings should be flexibly controlled according to climate and growing conditions. It is advisable to keep the potting soil moisture in a semi-dry state. Generally, in spring and autumn, water once every 2-4 days, and in summer, once every 1-3 days. In clear, dry weather, water more; in cloudy and rainy weather, water less or not at all. Osmanthus avoids dampness, and stagnant water in the pot must be strictly avoided, especially during the autumn flowering period, as excessive moisture will cause flower drop.
[Pruning Methods]
Winter pruning is the main method, carried out every year in early spring. During the first winter pruning, according to the size, height and plant shape of the seedling, shorten the main trunk by 1/4-1/3 to encourage adventitious buds on the lower part to sprout new branches, and properly prune overly dense branches. In later pruning, first remove dead branches, thin and weak branches, and diseased or pest-damaged branches, then retain 3-5 side branches that have short internodes at their growing positions, moderate spreading angles and even spatial distribution, and remove all other sprouting branches. In pruning the next year, for side branches that grow too vigorously, after retaining some branches at the base as flowering branches, shorten the vigorous growing part so that it grows in coordination with other side branches. At the same time, remove the water sprouts growing in summer and autumn, and according to need control plant height. Combined with pinching and pressing down lower branches, form a good crown structure.
[Structuring Methods]
Proceed according to the tree. Set the main framework well according to the tree form, remove other sprouting shoots, overly dense branches, water sprouts, crossing branches, and diseased or weak branches, so as to improve ventilation and light penetration. For trees that are strong at the top and weak at the bottom, the upper branches can be shortened by 1/3 to make the overall tree vigor strong. At the same time, apply wound healing and antiseptic membrane to the pruning cuts to protect the wounds.
Processing: Osmanthus has strong sprouting ability and tolerates pruning. One or two years after potting, shape it during the plum rain season or after autumn flowering, adopting a method that combines bending and tying with pruning. The main trunk can be bent and tied into a curved-trunk form or slanting-trunk style; if the main trunk is relatively tall, it can be properly shortened so that new branches and trunks sprout from the base, preventing the lower part from being empty, or heavily prune the upper branches and overly dense branches to stimulate new branches from the lower part of the main trunk, maintain balance between upper and lower parts, and make the tree shape beautiful with luxuriant flowers and leaves.
Tree form: For osmanthus shaping, it is best to make curved-trunk style, slanting-trunk style or flowing style. The tree extends obliquely, with dense branches and leaves, simple and natural, and is most worth admiring. When in bloom, its rich fragrance fills the air and refreshing the heart