How to grow an osmanthus bonsai? Detailed cultivation techniques
Osmanthus is evergreen all year round, with lush branches and leaves, blooming in autumn and filling the air with fragrance. It is widely used in gardens, often as a landscape tree, planted singly, in pairs, or in clumps and groves. In Chinese classical gardens it is often combined with buildings, rocks and stones, with clump-forming shrub-type plants set near pavilions, terraces, towers and chambers. Let us take a look below at the cultivation techniques for osmanthus bonsai!
Propagation methods for osmanthus bonsai
1. Sowing: Osmanthus fruit usually ripens from April to May, and can be harvested when the skin turns from green to purplish black. Osmanthus seeds have after-ripening; they need at least half a year of sand storage. After harvest, sprinkle water and pile them to ferment, remove the flesh, place in a cool place to let the seeds air-dry naturally, and store mixed with sand. After sand storage they can be sown in autumn or spring. Before sowing, prepare the ground well and apply sufficient base fertilizer; they can also be sown in an indoor seedbed. When sowing, place the seed hilum facing sideways, so as to avoid the radicle and young stem curving, which would affect seedling growth in the future.
2. Grafting: For osmanthus grafting, the rootstock is mostly glossy privet (Ligustrum lucidum), small-leaf privet (Ligustrum quihoui), Chinese privet (Ligustrum sinense), water privet, etc. When propagating seedlings in large quantities, small-leaf privet is mostly used. Before spring sprouting, cut off the rootstock 5 cm above the ground, cut a robust 1- to 2-year-old osmanthus branch 10 to 12 cm long, shave one side of the base into a 2 to 3 cm cut surface, and shave the opposite side into a 45-degree small bevel. Make a vertical cut about 1/3 of the way along one side of the rootstock, about 2 to 3 cm deep, insert the scion into the cut, align the cambium, tie tightly with a plastic bag, then bury in soil for cultivation.
3. Cuttings: Usually before spring sprouting, use fully developed one-year-old branches, cut into 5 to 10 cm lengths, remove the lower leaves, keep 2 to 3 green leaves at the top, and insert into a river sand or loess seedbed at a spacing of 3*20 cm. After inserting, water or spray promptly, shade, and maintain a temperature of 20 to 25°C and a relative humidity of 85 to 90%. After 2 months they can take root and be transplanted.
4. Layering: Osmanthus can be divided into low layering and air layering. The low layering method is in spring to early summer, selecting a relatively robust lower part of a low-trunk mother tree, selecting 1- to 2-year-old branches at easily bendable positions, cutting with a sharp knife or ring-barking, pressing them into a 3 to 5 cm deep trench and fixing the pressed branch with a wooden stick. The air layering method is in spring, selecting 1- to 2-year-old robust branches from the mother tree, cutting a ring or ring-barking in the same way as low layering, then applying culture medium to the wound, tying tightly above and below with a plastic bag, and after rooting in autumn, cutting away from the mother plant for care.
Cultivation techniques for osmanthus bonsai
1. Choosing a pot: Osmanthus has green leaves and yellow flowers and is evergreen all year round. It is advisable to choose a relatively deep round pot or square pot, with the pot mouth diameter roughly equal to the spread of the osmanthus branches and leaves, which benefits root development and growth. For the pot material, purple clay pottery pots or glazed pottery pots are best. For color, purple or ochre is better, which can create a sharp contrast with the flowers and leaves and increase the ornamental effect.
2. Soil: Osmanthus likes fertilizer, so it is advisable to use fertile, loose, well-drained sandy loam. The culture soil for potted osmanthus is usually prepared from garden soil, composted manure and river sand in a ratio of 1B3 each. Attention must be paid to disinfection treatment, so as not to be infected by diseases and pests.
3. Planting: Osmanthus is best planted in early spring or autumn. Before potting, spread a layer of river sand or vermiculite on the bottom of the pot to facilitate aeration and drainage, then spread a layer of peat soil or fine mud about 2 to 3 cm thick on top, reaching 1B3 of the pot depth. Then, place the osmanthus seedling with its root ball into the pot, fill with culture soil, press firmly with fingers, and fill soil until near the pot mouth; the soil surface should be 2 to 3 cm lower than the pot mouth, so as to facilitate watering and fertilizing. After planting, water thoroughly, then move to a shaded place for about 10 days to let it “adapt to the pot” and gradually resume growth.
4. Shaping: 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, using a combination of bending and tying with pruning. The trunk can be bent and tied into a curved-trunk form or slanted-trunk style. If the trunk is relatively tall, it can be appropriately shortened to make the base sprout new branches and trunks, so that the lower part is not empty, or heavily prune the upper branches and overly dense branches to stimulate new branches from the lower part of the trunk, maintaining balance between top and bottom and making the tree shape beautiful with lush flowers and leaves.
5. Tree shape: For osmanthus styling, the curved-trunk style, slanted-trunk style or flowing style are best. The tree posture extends at an angle, with dense branches and leaves, simple and natural, most enjoyable to appreciate; when in bloom it is rich in fragrance and refreshing to the heart.
Management of osmanthus bonsai cultivation
1. Placement: Osmanthus tree bonsai is suitable for placement in a warm, sunny place, with appropriate shading in summer to avoid direct strong light. In areas north of the Yangtze River, it must be brought indoors for the winter, and a room temperature of 0 to 5°C is relatively safe. The following spring, around the time of Awakening of Insects, it can be taken outside.
2. Watering: For osmanthus tree pot soil, grasp the principle of not watering until dry, and watering thoroughly when watering. Generally, in spring and autumn water once every 3 to 4 days, in summer high temperatures water once a day, and in winter water once every 7 to 10 days. In summer, water in the morning and evening; in winter, water around noon, so that the water temperature is close to the soil temperature and does not cause sudden cold or heat that damages the root system. In autumn, water moderately, and in the plum rain season prevent the pot soil from becoming too wet or waterlogged.
3. Fertilizing: Osmanthus tree bonsai is mainly for flower viewing, so it should be supplied with sufficient fertilizer. When shoots sprout, apply nitrogen fertilizer 1 to 2 times to promote branch and leaf growth. Before flower bud differentiation and flowering, mainly apply phosphorus fertilizer. Before fertilizing, the pot soil should be slightly dry, and it is advisable to first loosen the soil so as to absorb the fertilizer. The day after fertilizing, water once. If using compost or manure, it must be fully decomposed before use. If using the chemical fertilizer superphosphate, its concentration must not exceed 2%.
4. Pruning: The shaping and pruning of osmanthus trees is best done after autumn, cutting off overly strong upper branches to balance the tree vigor. Overly dense branches should be thinned out, and diseased and weak branches removed, so that nutrients are concentrated and flowering is favored. Shaping and pruning combined with water and fertilizer management can improve the healthy growth of osmanthus bonsai and maintain a beautiful posture.
5. Repotting: Osmanthus bonsai can be repotted and have its soil changed once every 2 to 3 years. The new pot should be somewhat larger to facilitate osmanthus root growth. In combination with repotting, cut off part of the old roots and dead roots, pick out part of the old soil with a bamboo stick, replace with loose and fertile new culture soil, and place decomposed cake fertilizer at the bottom of the pot as base fertilizer. When filling soil, it must be pressed firmly; this can promote lush flowers and leaves in osmanthus.
6. Diseases: Common diseases of osmanthus include leaf spot, sooty mold, algal leaf spot, root rot, iron deficiency, etc., and prevention and control should be carried out according to the disease situation. Leaf spot, sooty mold and algal leaf spot can be controlled by spraying 0.5 Bordeaux mixture or 5% carbendazim 500 to 1000 times solution. For root rot, attention should be paid to keeping the soil loose and breathable, and not waterlogged. If root rot is caused by fungi, it can be irrigated at the roots with 200 to 300 times solution of amobam.
7. Pests: Common pests of osmanthus include sawflies, whiteflies, mites, long white scale insects, yellow stinging moths, etc. Sawflies, whiteflies and mites can be killed by spraying 100% dimethoate 1500 to 3000 times solution. For long white scale insects, besides manual brushing off, during the first and second instar nymph stages they can be killed by spraying 400% omethoate 1000 times solution or 40% fenitrothion 500 times solution.