The Latest Guide to Potted Osmanthus Tree Planting Techniques and Methods

Osmanthus is the common name for many trees in the genus Osmanthus of China, and it is widely used in landscaping. The main cultivated varieties include Jinguì (golden osmanthus), Yínguì (silver osmanthus), Dānguì (red osmanthus), and Yuègui (monthly osmanthus). Its cultivation history in China spans more than 2500 years, and since ancient times it has been deeply loved by the Chinese people and regarded as a traditional famous flower. Now let us take a look together at the techniques for growing potted osmanthus trees!

Growing Environment for Osmanthus Trees

1. Temperature: Osmanthus trees like warmth. The average temperature in growing regions is 14-28°C, the average July temperature is 24-28°C, and the average January temperature is above 0°C. They can tolerate a minimum temperature of -13°C, and the most suitable growing temperature is 15-28°C. In areas of China south of the Qinling Mountains and the Huai River, they can overwinter outdoors. They are not very cold-resistant, but compared with other evergreen broadleaf tree species, they are still a relatively cold-resistant species.

2. Water: Osmanthus trees like moisture, and humidity is extremely important for their growth and development. They require an average annual humidity of 75-85% and annual precipitation of about 1000 mm. Especially during the young stage and when mature trees are flowering, they need more water; if drought occurs, flowering will be affected. Waterlogging must be avoided, but they also have a certain ability to tolerate drought.

3. Light: Osmanthus prefers sunlight but can also tolerate shade. Under full sunlight, its branches and leaves grow luxuriantly and it blooms profusely; in shady places, the branches and leaves are sparse and the flowers are few. If potted indoors in the north, special attention must be paid to providing sufficient light to promote growth and flower bud formation. Strong sunlight and deep shade are unfavorable for its growth. Generally, 6-8 hours of light per day is required.

4. Soil: Osmanthus is not very demanding about soil. Except for alkaline soil, low-lying land, or soil that is too heavy and poorly drained, it can generally grow. However, deep, loose, fertile, well-drained, slightly acidic sandy loam is most suitable.

5. Air: Osmanthus has a certain resistance to harmful gases such as chlorine, sulfur dioxide, and hydrogen fluoride, and also has a relatively strong ability to absorb and retain dust. It is suitable for planting in ventilated and light-transmitting places. It likes a clean and well-ventilated environment and is not tolerant of smoke and dust damage; after being harmed, it often fails to bloom.

Propagation Techniques for Osmanthus Trees

1. Sowing: Osmanthus fruit usually matures in April-May. When the fruit skin changes from green to purplish black, it can be harvested. Osmanthus seeds have after-ripening; they need at least half a year of sand storage. After harvesting, sprinkle water and pile them to ferment, remove the pulp, place them in a cool place to let the seeds dry naturally, and store them mixed with sand. After sand storage, they can be sown in autumn or spring. Before sowing, prepare the land well and apply sufficient base fertilizer; they can also be sown in indoor seedbeds. When sowing, place the seed hilum facing sideways to avoid bending of the radicle and young stem, which would affect seedling growth in the future.

2. Grafting: For osmanthus grafting, rootstocks are often Ligustrum lucidum, Ligustrum sinense, Ligustrum quihoui, Ligustrum obtusifolium, etc. For large-scale propagation of seedlings, Ligustrum sinense is often used. Before spring germination, cut off the rootstock 5 cm above the ground. Cut 1-2-year-old strong osmanthus branches 10-12 cm long, whittle one side of the base into a 2-3 cm cut surface, and cut the opposite side into a small 45-degree slope. Make a vertical cut about one-third of the way along one side of the rootstock, about 2-3 cm deep. Insert the scion into the cut so that the cambium layers align, tie tightly with a plastic bag, and then cover with soil for cultivation.

3. Cuttings: Osmanthus cuttings are usually taken before spring germination using fully developed one-year-old branches, cut into 5-10 cm lengths, with the lower leaves removed and 2-3 green leaves kept at the top. Insert them into river sand or loess seedbeds at a spacing of 3*20 cm. After insertion, water or spray promptly and provide shade, maintaining a temperature of 20-25°C and relative humidity of 85-90%. After 2 months, they can root and be transplanted.

4. Layering: Osmanthus can be propagated by low layering and air layering. The low layering method is to select relatively strong 1-2-year-old branches on the lower part of a low-trunk mother tree from spring to early summer, choose a part that bends easily, cut or girdle it with a sharp knife, press it into a 3-5 cm deep trench, and fix the pressed branch with a wooden stick. The air layering method is to select 1-2-year-old strong branches from the mother tree in spring, cut a ring or girdle them as in the low layering method, then smear the wound with a culture medium, tie plastic bags tightly above and below, and in autumn after roots develop, cut them from the mother plant for care.

Planting Techniques for Osmanthus Trees

1. Pot selection: Osmanthus has green leaves and yellow flowers and remains evergreen through the four seasons. It is best to choose a relatively deep round or square pot. The diameter of the pot opening should roughly match the spread of the osmanthus branches and leaves, which benefits root development and growth. For pot material, purple clay ceramic pots or glazed ceramic pots are best. Purple or ochre colors are better, as they can create a sharp contrast with the flowers and leaves and increase the ornamental effect.

2. Soil: Osmanthus likes fertilizer and is suitable for 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 a ratio of 1B3 each. Attention must be paid to disinfection treatment so that pests and diseases are not introduced.

3. Planting: Osmanthus is best planted 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, 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 its root ball into the pot, fill with culture soil, press firmly with your fingers, and fill soil until near the pot rim. The soil surface should be 2-3 cm lower than the pot rim to make watering and fertilizing easier. After planting, water thoroughly, then move it to a shaded place for about 10 days so that it can “adapt to the pot” and gradually resume growth.

4. Watering: For potted osmanthus trees, follow the principle of not watering until the soil is dry, and watering thoroughly when you do water. Generally, in spring and autumn, water once every 3-4 days; in summer high temperatures, water once a day; in winter, water once every 7-10 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 roots. In autumn, watering should be moderate, and during the plum rain season, prevent the potting soil from becoming too wet or waterlogged.

5. Fertilizing: Osmanthus bonsai is mainly grown for its flowers, so sufficient fertilizer should be supplied. When new shoots emerge, nitrogen fertilizer can be applied 1-2 times to promote branch and leaf growth. Before flower bud differentiation and flowering, phosphorus fertilizer should be the main application. Before fertilizing, the potting soil should be slightly dry, and it is best to loosen the soil first so that the fertilizer can be absorbed. On the second day after fertilizing, water once. If compost or manure is used, it must be completely decomposed before use. If chemical fertilizer superphosphate is used, its concentration must not exceed 2%.

6. Pruning: Shaping and pruning of osmanthus trees is best done after autumn. Cut off overly strong upper branches to balance the tree's vigor. Dense branches should be thinned out, and diseased and weak branches removed, so that nutrients are concentrated and flowering is promoted. Shaping and pruning combined with water and fertilizer management can improve the healthy growth of potted osmanthus and maintain a beautiful form.

7. Repotting: Potted osmanthus can be repotted and have its soil changed once every 2-3 years. The new pot should be slightly larger to facilitate root growth. Along with repotting, cut off some old roots and dead roots, remove some old soil with a bamboo stick, replace it with loose and fertile new culture soil, and place decomposed cake fertilizer at the bottom of the pot as base fertilizer. When filling with soil, it must be pressed firmly. This can promote lush flowers and leaves in osmanthus.

8. Diseases: Common diseases of osmanthus include leaf spot, sooty mold, algal spot, root rot, and iron deficiency, and prevention and control should be carried out according to the disease situation. Leaf spot, sooty mold, and algal spot can be controlled by spraying 0.5 Bordeaux mixture or 5% carbendazim 500-1000 times solution. For root rot, attention should be paid to keeping the soil loose and breathable, and avoiding waterlogging. If root rot is caused by fungi, 200-300 times solution of amobam can be used to irrigate the roots.

9. Pests: Common pests of osmanthus include sawflies, whiteflies, mites, white peach scale, and yellow slug moths. Sawflies, whiteflies, and mites can be killed by spraying 100% dimethoate 1500-3000 times solution. For white peach scale, in addition to manual brushing off, during the first and second instar nymph stages, 400% omethoate 1000 times solution or 40% fenitrothion 500 times solution can be sprayed for control.