Bittersweet Tree

Bittersweet Tree

Bittersweet Tree

Someone should produce a horror flick about how Oriental bittersweet (Celastrus orbiculatus) can single-handedly strangle neighboring mature trees if left to its own devices. This woody vine grows rapidly and has a twining nature that clings to anything going up or down. It can easily climb trees up to 90 feet tall. As the plant grows in diameter, it literally chokes or girdles other plants that it is clinging to. Its rate of spread is a bit like a Jack-in-the-bean-stalk fairy tale and it has been observed covering half-acre wood lots in just seven to 10 years. Between the girdling growth habit and sheer weight, whole canopies of a forest can tumble down during the growing season or an ice storm. The Bittersweet Tree is a new blog that tackles all the topics and issues that are important to pediatric oncology patients and caregivers.



Oriental bittersweet commonly occurs along the edge of a road where infestations are easily noticed and harvested by “unsuspecting” collectors. Broadly-oval, glossy leaves bear fine teeth and can be 2 to 5 inches long. Insignificant, light-colored flowers appear in May and June on separate male and female plants, like holly. This can be seen this time of year when some plants are clearly without fruit, growing right next to one that has fruit.In some places, Oriental bittersweet is rapidly taking over US forests, smothering any tree and shrub that it comes in contact with. This vine grows vertically, entwining tree trunks and strangling the tree as it grows. Thick mats of bittersweet can grow up as high as 90 feet, making tall trees more susceptible to wind and ice damage. Bittersweet in the forest canopy also captures most of the sunlight and water needed by other vegetation. Thick growths of bittersweet can cover forest floors, smothering saplings and other ground vegetation. The invasive behavior of Oriental bittersweet affects the makeup of forests, harming much of the native vegetation.

Oriental bittersweet originated in eastern China, Korea, and Japan, and was introduced to the US in the 1860s as an ornamental plant. In less than 200 years Oriental bittersweet spread from Maine to North Carolina, and as far west as Wisconsin and Missouri. It grows in a variety of habitats from forests to open fields, beaches, marshes, roadsides, and hedgerows. In a 2004 study, bittersweet grew best in areas of high activity (such as along roads) because the forest floor litter (fallen leaves, twigs, dirt, etc.) is not too thick. Bittersweet seeds have thin coats and don’t survive well under thick litter for long periods of time. The researchers concluded that bittersweet grows well in thin litter, such as that found in pine forests or along roadsides. These areas are more prone to bittersweet invasion. You can recognize Oriental bittersweet by its spiraling growth up tree trunks. You can also recognize it by its fruits, which grow along vines in groups of 1-3 and are green in summer, turning orange-yellow in late fall. The bright red, fleshy fruit is exposed in the fall when the fruit’s outer skin splits open. Its leaves are glossy, 2-5 inches long, oval-shaped coming to a point, and with fine teeth along the edges. They are green in spring and summer and turn gold in the fall. Mature bittersweet vines are light brown and can be 4 inches thick; young vines are thin, green, and covered in small, lightly colored bumps called lenticels. There is also a native bittersweet species, American bittersweet, that is not as destructive as Oriental bittersweet, but it is difficult to distinguish between the two species. The best way to identify one species from another is to look at their fruit clusters. Look for the stems, which branch off of the vines. Oriental bittersweet’s fruits grow along the length of stems, whereas American bittersweet’s fruits only grow at the end of stems. (Source: mdocs.skidmore.edu)



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