How to Cultivate Golden Osmanthus Trees? Detailed Guide to Planting Techniques and Care Methods
Golden osmanthus (Osmanthus fragrans 'Jingui') is an evergreen broadleaf tree of the genus Osmanthus in the family Oleaceae. It has luxuriant foliage year-round, with golden-yellow flowers that are elegant without being delicate, and a rich fragrance that is subtle yet not overpowering. Among the many osmanthus varieties, it has the highest ornamental value, and its flower color, fragrance and flower quantity are comprehensively superior, making it a sought-after species for introduction and cultivation in gardens across southern China, especially for ornamental cultivation. Let us take a look at the cultivation techniques for golden osmanthus trees below!
Ecological Habits of Golden Osmanthus
Golden osmanthus is adapted to subtropical climate regions. It prefers warmth and moisture, can tolerate a minimum temperature of -13°C, and its optimum growth temperature is 15-28°C. It requires an average annual humidity of 75-85% and annual precipitation of around 1000 mm. It has strong stress resistance, prefers sunlight but also tolerates shade. Under full sunlight, its branches and leaves grow luxuriantly and it blooms profusely; in shaded areas, its branches and leaves are sparse and flowers are few. It is not very demanding regarding soil, and can generally grow in any soil except alkaline soil, low-lying areas, or overly heavy, poorly drained soil. However, deep, loose, fertile, well-drained slightly acidic sandy loam is most suitable. It has a certain resistance to harmful gases such as chlorine, sulfur dioxide and hydrogen fluoride, and also has a strong ability to absorb and retain dust, so it is often used in cities and industrial and mining areas.
Propagation Techniques for Golden Osmanthus
1. Layering propagation: Usually at the end of March and beginning of April, around the mother plant, depending on the number of branches that can be layered, dig a small trench 20 cm deep and 20 cm wide along the direction in which the branches naturally extend, then bend the branches down into the trench, fill the trench with fertile soil and firm it by treading, water thoroughly, and then mound the soil at the layered portion into a steamed bun shape.
2. Air layering: Usually between September and October, split one section of a moso bamboo tube into 2 pieces, fill it with moist soil, and fit it over a vigorous branch of a superior osmanthus variety. Support it with a frame, add water frequently to keep the inside of the tube moist. After more than 1 month, new roots will grow. In the following spring, remove and transplant it to form a osmanthus tree, which can bloom in about 3 years.
3. Seed propagation: Every year at the end of May and beginning of June, pick the ripe drupes from osmanthus trees, remove the outer shell, dry them slightly in the shade, and store them in moist sand. In early spring of the following year, broadcast sow them on a pre-prepared seedbed. When the weather warms up in March, they will germinate and take root. Generally, seedlings can reach about 15 cm in height in one year, and can grow to 1 m tall in 2 to 3 years, at which point they can be lifted from the nursery and planted out.
4. Grafting propagation: Select one-year-old vigorous lateral branches from a plant about 20 years old, cut off two bud scales, graft them onto a privet (Ligustrum) rootstock, wrap with strips cut from plastic film, and they can sprout in the same season. They can bloom after 4 years, but osmanthus trees propagated by this method have crooked trunks and are not suitable for use as street greening trees.
5. Cutting propagation: Choose February, when the sap is about to start flowing, as the cutting season. One month before cutting, spray the cutting bed with trichlorfon 800-1000 times solution to kill nematodes. 10 to 15 days before cutting, disinfect again with limewater. 3 days before cutting, rinse the cutting bed with clean water. After cutting, firm the bed soil, cover the rows with grass, water thoroughly once, and set up a shade frame. When the new shoots that emerge grow to more than 6 cm, they can be moved out of the seedbed for cultivation.
Cultivation Techniques for Golden Osmanthus
1. Land preparation and fertilization: Choose acidic sandy loam with ample sunlight, deep soil layers, rich in humus, strong permeability, and convenient drainage and irrigation as the cultivation nursery site. In the autumn and winter of the year before transplanting, first plow the nursery land thoroughly once, and dig holes according to a plant-row spacing of 1×1.5 m and a planting hole size of 0.4×0.4×0.4 m. Apply 2-3 kg of decomposed farmyard manure of neutral nature and 0.5 kg of phosphate fertilizer per hole as base fertilizer. Mix the base fertilizer evenly with the surface loam and fill it into the holes. After the fertilizer is eroded and fermented by winter snow and spring rain, it is easily absorbed by the saplings.
2. Timely transplanting: Golden osmanthus is best transplanted when the sap has not yet flowed or has just begun to flow, generally from early February to early March. When lifting seedlings, keep as many roots as possible and damage as few roots as possible. After lifting, plant as soon as possible. If seedlings need to be transferred from other places, pay attention to moisture retention to prevent the seedlings from dehydrating. After planting, firm the soil and water thoroughly once so that the seedling roots are in close contact with the soil.
3. Water and fertilizer management: After transplanting golden osmanthus, if heavy rain causes waterlogging in the nursery, dig trenches to drain the water. In case of drought, water to combat it. In addition to applying sufficient base fertilizer, apply fertilizer 3 times each year: in late March, apply 0.1-0.3 kg of quick-acting nitrogen fertilizer per plant to promote height growth and more new shoots; in July, apply 0.1-0.3 kg of quick-acting phosphorus and potassium fertilizer per plant to improve its drought resistance; in October, apply 2-3 kg of organic fertilizer (such as farmyard manure) per plant to improve its cold resistance and prepare for overwintering.
4. Pruning and shaping: Golden osmanthus sprouts new shoots twice each year in spring and autumn. If not pruned and the buds not removed in time, it is difficult to cultivate tall plants, and it easily forms a phenomenon of dense upper branches and sparse lower branches, strong at the top and weak at the bottom. When pruning, in addition to shortening branches whose tree vigor or branch vigor is poor, generally thinning is the main approach. Promptly remove the sprouting branches that emerge from the base of the trunk to avoid consuming nutrients within the tree and disrupting the tree shape.
5. Loosening soil and weeding: For golden osmanthus in spring and autumn, carry out one intertillage each in conjunction with fertilization to improve soil structure. Before overwintering, mound the base once and whitewash the trunk once to enhance cold resistance. Weed 2-3 times each year to prevent weeds from competing with the seedlings for water, fertilizer and light.