Oriental bittersweet

Celastrus flagellaris, also known as climbing bittersweet, is a deciduous vine in the family Celastraceae, genus Celastrus. Its branches and vines can reach more than 10 m in length. The twigs have short hook-like stipular spines curved downward, and the simple leaves are alternate and elliptical. The margins have fine serrations, and the tips of the teeth are spine-like. The short racemes are axillary, the petals are spoon-shaped and oblong, and the flowers are yellow-green, blooming from June to July. The capsules are spherical and split open when mature, with white seeds wrapped in a bright red aril.

Celastrus flagellaris is native to Northeast China, North China, and other places. It likes sunlight and tolerates shade, has a wide distribution, is cold-resistant and drought-tolerant, and has no strict requirements for soil. It grows best when planted in fertile sandy loam that is sheltered from the wind, sunny, moist, and well-drained; if planted in partial shade, it can also grow. When fertilizing, 2 to 3 kg of decomposed organic fertilizer can be applied into the pit at planting time, and some organic fertilizer can be applied each autumn thereafter, which can make the plant grow vigorously and produce large, brightly colored flowers. For watering, water once each before bud break in spring and before early winter; during the growing period, if the weather is not too dry, there is no need to water. It should be noted that although Celastrus flagellaris likes moisture, it cannot tolerate long-term waterlogging, so drainage should be done promptly after rain. If you want to grow Celastrus flagellaris into a shrub form, shorten it after leaf fall in winter to encourage more side branches. Next, prune diseased, pest-damaged, and weak branches to make the plant's crown full. If it is used for vertical greening, a support or trellis must be set up, otherwise growth will be restricted. In addition, its twining ability is very strong. If there are other trees around it, check at any time to prevent them from being climbed on by it. The main pests and diseases of Celastrus flagellaris are those caused by the prickly slug moth and red spider mite. If they occur, spraying with 50% phoxim emulsifiable concentrate at 1000 to 1500 times dilution gives good results.

Celastrus flagellaris can be propagated by sowing, division, or cuttings, but sowing is mostly used, and both autumn sowing and spring sowing are possible. If sowing in spring, the seeds should be soaked in 45-degree warm water for 24 hours and stirred thoroughly. Change the water once a day. After 2 days, remove the seeds, drain them, soak them in 0.3% to 0.5% potassium permanganate solution for 1 hour, wash them, and drain them. Then mix them with 3 times their volume of moist sand, keeping the sand's moisture content at 60%, and then stratify them in sand. This method can promote softening of the seed coat of Celastrus flagellaris and enhance its ability to absorb water and swell, and the treatment time is 30 to 40 days. Twenty days before spring sowing, place the sand-stratified seeds indoors or in a wind-sheltered, sunny place, keep them at 10°C to 15°C, and turn them 1 to 2 times at noon every day. When more than one third of the seeds have sprouted white, they can be sown.

Celastrus flagellaris has dense branches and lush leaves. In autumn the leaves turn yellow, and the capsules split open to reveal seeds wrapped in red arils, resembling red flowers. It is an excellent tree species for trellises and vertical greening. It can also be shaped into a shrub beside rivers and pond banks, and its reflection in the water is also very distinctive.