Koelrenteria paniculata, commonly known as the lantern tree, is a species belonging to the Eucalyptus genus. This deciduous tree exhibits striking seasonal changes: its spring leaves are red, while autumn leaves turn bright yellow, and its flowers appear in full bloom during the flowering season. One of the most distinctive features of this tree is the membranous pericarp of its seed pods, which swell like small lanterns before and after National Day, turning bright red and hanging from the branches like decorative flowers. The tree has strong resistance to dust and pollution, making it an ideal choice for urban landscaping.
Eucalyptus trees are typically propagated through sowing. Below are the key steps involved in the seeding and propagation process:
**Seed Collection:**
Seeds usually mature between September and October. It is important to select high-quality mother trees for seed collection. The best time for harvesting is from late October to early November, when the spherical seeds turn brown. If not collected promptly, they may fall off naturally. After collection, the fruits should be dried in the sun or spread out to dry. Once the capsules crack open, the seeds can be beaten and threshed. After drying, the membranous husks and other impurities are removed to obtain clean seeds. These seeds are then air-dried for 5 to 7 days and stored in bags or paper sacks. In mid-December, the seeds are mixed with wet sand (more than five times their volume) and stacked in a room at a height of 25 to 30 cm. A layer of grass cover is placed on top, and the mixture is turned regularly to maintain moisture at around 15%.
**Sowing:**
Eucalyptus is generally grown using field seedlings. Sowing typically occurs in March. The soil should be loose, well-drained, and rich in nutrients, free from pests and pathogens. It is recommended to till the land in autumn or winter one to three times to improve soil structure, retain moisture, and control weeds and pests. The soil should be smooth, fine, and ready for irrigation in dry areas. A base fertilizer is applied, along with granular insecticides such as furazolidone or zinc phosphite at a rate of 8 to 10 kg per mu. Raised beds are made with a width of 1.2 meters and a length of up to 20 meters. Due to the low germination rate of eucalyptus seeds, a large amount is used—about 60 to 120 grams per square meter. Broad-spectrum seeding is preferred to promote ventilation and ease of management. Five lines are sown in each bed, with ditches dug 3 cm deep. The seeds are mixed with sand and evenly distributed in the ditches, then covered with 2 cm of soil. Light treading is done, followed by a light watering, and straw is placed over the area. After about 25 days, the straw is removed. As most seedlings emerge, the covering is gradually lifted.
**Seedling Care:**
After the straw is removed, shading is necessary to protect young seedlings from sunburn. The duration and intensity of shading depend on local climate conditions. Gradually increasing light exposure helps the seedlings develop stronger lignification. When seedlings reach 5 to 10 cm in height, thinning is performed to ensure proper spacing—around 100 seedlings per 10 square meters. Weeding and fertilization are essential to promote healthy growth. Seedlings that fail to thrive in the fall can be transplanted in the spring.
**Transplanting:**
Eucalyptus is a deep-rooted species, and its trunk often requires straightening through dense planting or flattening techniques. Seedlings in the nursery are typically transplanted 3 to 4 times. During each transplant, the main root and thick lateral roots should be trimmed to encourage the development of fibrous roots, which aids in future establishment. The first transplant should be done carefully to ensure a straight trunk, saving space and improving management. In spring, new buds emerge from the base, and the strongest ones are selected as trunks. If the first trimming does not meet requirements, a second round can be done in the following spring. Every three years, the main and thick lateral roots should be properly cut to stimulate new root growth. One-year-old seedlings can reach heights of 80 to 100 cm.
**Seedling Management:**
Once the roots are established, fertilization should be combined with watering. During the growing season, nitrogen-based fertilizers are applied to support vegetative growth. In autumn, nitrogen is reduced, and phosphorus and potassium are added to increase lignification and cold resistance. In winter, organic fertilizer is used as a base to provide long-term nutrients and help insulate the soil. Regular weeding, watering, and soil loosening are essential. By the end of autumn, seedlings can grow to 1.8 to 2 meters tall, with a diameter of about 2 to 2.5 cm. They are graded and transplanted in the following spring, with roots trimmed before planting. After transplanting, the rhizomes are cut, and the seedlings are watered thoroughly. Bud removal is performed to allow the strongest buds to develop into trunks. Throughout the growing season, soil aeration, weeding, watering, and topdressing are maintained. After a few years, the seedlings can be prepared for garden planting.
**Pruning:**
The crown of the eucalyptus tree is nearly spherical, and pruning needs vary depending on its intended use. For street trees, the main trunk must be straight, with the first branch at 2.8 to 3.5 meters. The crown should be full, with evenly distributed branches. For shade trees, a lower first branch height is preferred. Pruning should be done in winter or during transplantation to meet these standards. In addition, regular weeding, irrigation, and drainage are essential for healthy growth. While eucalyptus is generally resistant to diseases and pests, prompt treatment is necessary if any issues arise.
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