Propagation Methods and Landscaping Applications of Celastrus flagellaris
Celastrus flagellaris, also known as pricklyleaf bittersweet and prickly bittersweet, is a deciduous climbing plant in the genus Celastrus of the family Celastraceae.
1 Botanical Characteristics
A climbing shrub, growing in clumps or singly, creeping along the ground or twining up tree trunks, 10-15 m long, bark reddish-brown, green when young. Branchlets smooth, with hard hooked prickles 1.5-2.5 mm long. Branchlets have short hooked-spine-like stipules, curving downward. Leaves alternate, elliptic, ovate or round, 4-8 cm long and 3-5 cm wide, apex relatively broad, with a short point or a very short acuminate tip, base gradually narrowing, margins with ciliate fine serrations or serrations, the tooth tips often forming fine hard spines; 4-5 pairs of lateral veins, the midvein with fine sparse short hairs or nearly glabrous; petioles slender, flowers often solitary, cymes axillary, 1-5 flowers or more, inflorescence nearly sessile or with a peduncle 1-2 mm long, disk shallowly cup-shaped, apex nearly truncate, petals spoon-shaped oblong, flowers yellow-green; capsules flattened-globose, 2-8 mm in diameter, splitting into 3 valves at maturity; seeds nearly elliptic, about 3 mm long, yellowish-brown, flowering period in May-June, fruit ripening period in August-September.
2 Biological Characteristics
Celastrus flagellaris prefers sun and tolerates shade, has a wide distribution, is cold-resistant and drought-tolerant, and is not demanding about soil. It prefers damp, shaded places, often growing in valleys, low damp riverside sites at forest edges or in shrub thickets, tolerating shade. It is native to the Lesser Khingan and Zhangguangcai Ling mountain areas of Heilongjiang Province, and is also distributed in Liaoning, Jilin and North China.
Celastrus flagellaris has luxuriant branches and leaves; in autumn the leaves turn golden yellow, and the capsules split open to reveal seeds wrapped in red arils, resembling red flowers, making it an excellent material for trellises and vertical greening. It is naturally shade-tolerant and moisture-loving, suitable for planting under forest canopies and along banks, and can also be shaped and pruned into a shrub for vertical greening of rockeries, embankments and walls. Because it has been little developed and utilized, it remains in a natural wild state to this day, and is a native tree species of relatively high development value for urban three-dimensional greening in northern regions; in addition, it is also a medicinal plant.
3 Propagation Techniques
Under natural conditions, Celastrus flagellaris reproduces by seed and tillering. Under artificial conditions, sowing, division and cutting propagation can be used.
3.1 Sowing and Seedling Raising
For sowing and seedling raising, spring sowing is preferable. Collect seeds in September-October, dry them in the shade, remove the outer seed coat, place them in a breathable bag and store in a cool, dry place. In mid-to-late February, carry out stratification treatment, then soak in 45°C warm water, stir thoroughly, let cool naturally, change the clean water twice a day; after 2 days, remove the seeds, drain them, soak in 0.5% potassium permanganate solution for 1 hour, then remove, rinse with clean water and drain. Mix the seeds with fine sand at a volume ratio of seeds:sand of 1:3; keep the sand moisture content at 60% (squeeze into a ball that holds together, then crumbles when dropped) as appropriate, and place in a 0-5°C environment for sand storage, with a treatment time of about 45 days. 15 days before sowing, place the sand-stored seeds indoors or in a sheltered sunny spot, maintain 10-15°C, and turn them 1-2 times at noon each day; if germination is slow, cover with plastic film to keep warm and moist. When more than 1/3 of the seeds have "whitened" (radicles emerging), they can be sown. Use bed planting or ridge planting, drilling is preferable; prepare the soil carefully, sow mixed with sand at a density of 400-500 seeds per sq m, and cover with 1 cm of soil. To increase seed germination speed, cover the seedbed with plastic film, remove the film after seedlings emerge, and full emergence occurs in 3-4 weeks; weed and water promptly, apply liquid fertilizer 3 times, with phosphorus and potassium fertilizers mainly in autumn. Before freezing, water to prevent frost damage, cover with 5 cm of soil to overwinter, and the following spring the seedlings can be lifted for transplanting or used for greening.
3.2 Cutting Propagation
Branches from all parts of Celastrus flagellaris can root when cut, but softwood cuttings give better rooting results. In July-August, in conjunction with pruning, select semi-lignified branches, cut them into 10-12 cm long cuttings, remove the lower leaves, keep 1-2 upper leaves, tie 50 into a bundle, align the lower cut ends, and dip in 5×10-5 NAA solution for 30 minutes. In a greenhouse or seedling box, spread fine sand 10 cm thick, disinfect with chlorothalonil, level the bed surface, make holes with a bamboo stick at a spacing of 3×3 cm, insert the cuttings into the seedbed to a depth of 5-6 cm, spray with water, then cover with plastic film to retain moisture, shade with a shade net at 60%, control the temperature at 21-23°C, spray water 3 times a day; rooting occurs in 12-14 days. After rooting, remove the film, expose to moderate light, and later spray foliar fertilizer to promote above-ground growth; they can also be potted.
4 Landscaping Applications
Celastrus flagellaris has strong natural survival ability and strong natural creeping and climbing ability, but it is rarely used in landscaping. The author has used it in campus landscaping since 1990 with good results. The main application methods are the following 3:
4.1 Ground Cover Cultivation
Celastrus flagellaris is both moisture-loving and drought-tolerant, with strong adaptability, and has a very good effect when covering bare plots such as embankments, watersides and slopes. Because of its strong natural creeping ability, it can quickly cover the ground surface, and at the same time the places where branches and vines touch the ground can produce a large number of adventitious roots, giving it even better soil-fixing and slope-protecting ability than Boston ivy. For ground cover cultivation, the planting density depends on seedling age; for 2-year-old sown seedlings or 1-year-old cutting seedlings, plant at a spacing of 40×40 cm between plants and rows, and they can cover the ground in 2 years; if the density is increased to 20×20 cm, they can cover the ground in the same year. After planting, weed promptly; no pruning is needed, only preventing fire in autumn and winter. Ground cover that has covered for more than 5 years can be heavily pruned to thin the plants, or pruned in summer in conjunction with cutting propagation, to reduce the coverage thickness. Because this ground cover is dense and densely covered with hooked prickles, it should be used with caution in scenes such as primary school campuses and kindergartens.
4.2 Vertical Greening
Celastrus flagellaris has strong natural climbing ability, climbing by twining its branchlets and hooking onto other objects with its stipular spines, attaching tightly and with strong wind resistance, forming a stable vertical greening effect; in addition, its new leaves are tender green, its autumn leaves golden yellow, and its fruits crack open after frost to reveal red arils, giving it high ornamental value. Celastrus flagellaris can be arranged on various trellises, walls and stump specimens; walls need climbing supports, while other forms climb naturally according to their shape. For trellis greening, in the initial planting period, appropriate manual guidance of direction is needed so that it climbs upward as early as possible. To achieve a landscape quickly, large seedlings with main vines over 2 m should be selected for planting; surviving large seedlings grow 1-2 m per year and can quickly form a landscape. Celastrus flagellaris has a good effect when used for greening fences or protective walls; it can both beautify the wall and serve as a protective material. In the initial climbing period, a wire should be stretched or wooden strips nailed on the wall every 30 cm to provide attachment points for the branches to hook and climb; after the set branches reach the top of the wall, they can climb naturally, and moderate pruning and shaping each year is sufficient. For trellis-type greening, moderate pruning and shaping are needed each year; when branches become too dense, they need to be renewed from the lower part, leaving 1 long vine at the top and cutting away all the rest.
4.3 Shrub Cultivation
After shaping and pruning management, Celastrus flagellaris can be cultivated in shrub form, forming various shapes such as spherical, umbrella-shaped, spreading and pendulous. In the seedling stage, supports need to be set up manually to guide it upward; during the growing period, pinch the tips to promote side branches, while accumulating nutrients to thicken the main trunk so that the trunk can stand naturally upright. The trunk can be raised 20-30 cm each year; to increase trunk thickness, bundle 3-5 seedlings together and plant them at the first planting, and in 3 years the trunk can be raised to about 1 m. In summer, promptly prune excessively fast-growing branches and vines to prevent the branches of 2 trees from joining, reduce the main branches to promote side branches, and make the crown full and round. For the pendulous form, bamboo poles or wire need to be added manually at the top for guidance; after the branches lignify, the new branches droop naturally.
4.4 Cultivation Precautions
Celastrus flagellaris plants grow vigorously and like moisture, but the planting site must not have standing water. Because of its strong twining and covering ability, if there are other trees around it, they should be checked at any time to prevent them from being climbed on; however, some dead trees can be used by it to climb on and regain a greening effect. The main pests and diseases of Celastrus flagellaris are slug moths and red spider mites; if they occur, spray with 50% phoxim emulsifiable concentrate at 1000 times dilution, which gives good results.