How to Grow Osmanthus? Detailed Guide to Cultivation Methods and Precautions

Osmanthus is the common name for many trees in the Chinese genus Osmanthus, also known as rock osmanthus, wood osmanthus, golden millet, etc. It is an excellent garden tree species that combines greening, beautification, and fragrance, with both ornamental and practical value. Its fragrance is pure enough to cleanse the dust and strong enough to carry far, making it truly unique. Since ancient times it has been deeply loved by Chinese people and regarded as a traditional famous flower. Now let us take a look at the cultivation methods and precautions for osmanthus!

Growth Habits of Osmanthus

1. Osmanthus prefers warmth and has strong stress resistance. It tolerates both high temperatures and fairly cold conditions, and can overwinter outdoors in areas south of the Qinling Mountains and the Huaihe River in China.

2. Osmanthus prefers sunlight but also tolerates shade. Under full light its branches and leaves grow luxuriantly and it blooms profusely; in shady places its branches and leaves are sparse and flowers are few.

3. Osmanthus likes moisture but fears waterlogging and standing water. However, it also has a certain tolerance to drought. If subjected to waterlogging damage, the entire plant may die.

4. Osmanthus is not strict about soil requirements. It can generally grow in any soil except alkaline soil, low-lying land, or soil that is too heavy and clayey with poor drainage.

Propagation Methods of Osmanthus

1. Sowing: Osmanthus fruit usually matures from April to May. After harvesting, sprinkle with water and pile to compost, 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 indoor seedbeds. When sowing, place the seed hilum sideways to prevent the radicle and young stem from bending, which would affect seedling growth in the future.

2. Grafting: For osmanthus, before spring sprouting, cut the rootstock off 5 cm above the ground. Cut a vigorous 1- to 2-year-old osmanthus branch 10 to 12 cm long. Carve one side of the base into a 2 to 3 cm cut surface, and carve the opposite side into a small 45-degree slope. 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 layers, tie tightly with a plastic bag, and then bury in soil for cultivation.

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

4. Layering: The low layering method for osmanthus is carried out from spring to early summer. Select a relatively thick low-growing mother tree and choose 1- to 2-year-old branches on the lower part. Select an easily bendable section, use a sharp knife to cut or girdle it, press it into a 3 to 5 cm deep trench, and fix the pressed branch with a wooden stick. The high layering method is done in spring by selecting 1- to 2-year-old thick branches from the mother tree, cutting a ring or girdling in the same way as the low layering method, then applying culture medium to the wound, tying tightly above and below with plastic bags, and after roots develop in autumn, cutting away from the mother plant for maintenance.

Cultivation Methods of Osmanthus

1. Potting soil: Osmanthus does not have high soil requirements. The potting soil can be a mix of humus soil or peat, garden soil, and sandy soil or river sand (ratio 5:3:2). After preparation, the pH should be maintained at 5.5 to 6.5. Before potting, disinfect the culture soil with a 0.1% potassium permanganate solution.

2. Watering: For osmanthus watering, grasp the principle of not watering until dry, and watering thoroughly when you do. Spray the leaves with clean water once a day. After Qingming Festival, move the osmanthus to the open air and water thoroughly once. In summer, water in the morning and evening; in winter, water around noon. Be careful not to let water accumulate.

3. Fertilizing: Osmanthus is mainly grown for its flowers, so it should be supplied with sufficient fertilizer. During shoot growth, apply nitrogen fertilizer 1 to 2 times. Before flower bud differentiation and flowering, mainly apply phosphorus fertilizer. Before fertilizing, the potting soil should be slightly dry, and it is best to loosen the soil first. On the second day after fertilizing, water once.

3. Repotting: Osmanthus usually needs repotting and soil replacement every 2 to 3 years. Cut away part of the old roots and dead roots. Place a layer of river sand or vermiculite at the bottom of the pot to facilitate aeration and drainage, and place decomposed cake fertilizer as base fertilizer. When filling soil, be sure to press it firmly.

4. Pruning: Shaping osmanthus is best done after autumn. For plants with a very poor tree shape, cut off all the top branches at 2/3 or 3/4 of the height. For plants with overly dense branches, thin them out. After flowering, also cut off leggy branches, dead branches, diseased and pest-infested branches, and dense weak branches.

5. Overwintering: The indoor temperature for overwintering osmanthus should be 0 to 5°C, with relative humidity of 50 to 80%. In winter, the cold room should have good light, especially before buds begin to sprout in early spring when sufficient sunlight is even more required. The following year after Grain Rain, arrange to move them outdoors. After moving out, first place them together in a wind-sheltered, sunny spot outdoors.

6. Diseases: Common diseases of osmanthus include leaf spot, sooty mold, algal spot, root rot, and iron deficiency. Leaf spot, sooty mold, and algal spot can be controlled by spraying Bordeaux mixture or carbendazim. For root rot, care should be taken to keep the soil loose and breathable, and avoid water accumulation.

7. Pests: Common pests of osmanthus include sawflies, whiteflies, mites, white peach scale, and yellow stinging caterpillars. Sawflies, whiteflies, and mites can be killed by spraying dimethoate. For white peach scale, besides manual brushing, it can be killed by spraying omethoate or fenitrothion during the first and second instar nymph stages.

Precautions for Osmanthus

1. Water management for potted osmanthus is quite difficult. Overwatering often causes leggy growth, while poor drainage and water accumulation in the pot easily cause root rot. Therefore, daily care must be careful not to water too much. Even in the early flowering stage when more water is needed, avoid making the potting soil too wet.

2. Osmanthus is a long-day plant and likes strong light. If the plant cannot receive sufficient light during the growth period, its branches and leaves will become leggy, affecting flower bud formation and resulting in failure to bloom. Therefore, do not shade excessively during cultivation.

3. If potted osmanthus is not repotted or given fresh soil for years, the plant will suffer from insufficient nutrition, and the root system will become root-bound and unable to spread, affecting flowering. For this reason, potted osmanthus should be repotted every 1 to 2 years, with a small amount of hoof pieces applied as base fertilizer, and more phosphorus and potassium fertilizer should be applied throughout the growing period.

4. After potted osmanthus is brought indoors in winter, it is best placed in a low-temperature location to let it go dormant. If the room temperature is relatively high, the osmanthus will not get sufficient dormancy, causing it to sprout and unfold leaves early, resulting in weak branches and consumption of large amounts of nutrients. After being moved outdoors in spring, it is prone to withering and dying when encountering dry wind.

5. Potted osmanthus is not tolerant of smoke and dust. If allowed to grow in places with polluted air, it will grow poorly, with smaller leaves that easily fall off, and few or no flowers. Therefore, during cultivation, prevent osmanthus from being polluted by smoke and dust.