While cranberry and pumpkin are plants native to the Americas that help satiate the palate at Thanksgiving, bittersweet is an American plant that can please the eyes. It is useful both in the home for Thanksgiving decoration or outdoors in the landscape. This woody vining plant with attractive orange-red berries grows in the wild over a goodly part of North America. Bittersweet not only adds color in the landscape at a time when color from other plants is sparse, it also is an important food source for birds. Its berries normally remain attractive until very cold weather causes them to darken and collapse.
The common name bittersweet is thought to have been given to the plant by 18th century European colonists who thought its fruits resembled those of European nightshade, a plant native to Eurasia that carries the common name of bittersweet. Today, the name is applied to two diecious species of the genus Celastrus. American bittersweet (Celastrus scandens) is commonly found along roadsides or on fences in central and eastern parts of the United States. Although a vigorous grower, it is not considered to be invasive. All parts of the plant are considered to be toxic, even though it is thought that Native Americans used the berries for medicinal purposes such as treating intestinal disorders.
Oriental bittersweet (Celastrus orbiculatus) was introduced from the Orient in the 19th century to be used as a landscape plant. It produces a greater abundance of berries than American bittersweet that (apparently) are more attractive to birds as a food source. As a result, Oriental bittersweet has spread to the wild where, although a colorful plant, it has become a threat to other vegetation. Oriental bittersweet can wrap itself so tightly around the trunk of small trees that it can strangle them by girdling and restricting sap flow. Additionally, it is capable of robbing nearby plants of needed nutrients. Oriental bittersweet also is considered to be toxic.
The easiest way to differentiate between the two is to note the size and location of the berries. Oriental bittersweet produces smaller berries in clusters produced from the leaf axils or near the ends of its shoots. American bittersweet produces larger berries in clusters at the terminals, or ends, of the lateral vines. In both cases the berries are borne in yellowish capsules that split open in the fall to reveal a bright orange-red aril. The latter is a botanical term given to the fleshy covering of a seed.
Gardeners contemplating adding bittersweet to their landscape either for themselves or for the sake of birds should choose the "better behaved" American bittersweet. Although not invasive, it is a vigorous vine that climbs by twining. American bittersweet can climb 20 feet or more into trees or anything that is nearby. When there is nothing to climb, such as when it is located on large slopes, it tends to sprawl over the ground and becomes a loosely-tangled groundcover.
Bittersweet is easy to grow and winter hardy through zone 3. It adapts well to many soil types and is a good choice for poor soils, where its growth will be less rampant. Additionally, it has no major insect or disease problems. Given its natural vigor, bittersweet should be cut back severely each winter to allow new growth to develop the subsequent spring. Bittersweet tolerates both sunny and shady exposures, but sun is needed for the plant to fruit well. It rarely requires supplemental water and is generally self-reliant.
Bittersweet can be started from seeds or cuttings. Since it is dioecious, fifty percent of the seeds of bittersweet will produce male plants and fifty percent female. Unfortunately, it is not possible to tell the sexes apart until the vines become large enough to flower. For good berry production, both sexes must be present. Where space is limited, plant at least three plants close together. This (hopefully) will result in a mix of both sexes.
When growing bittersweet from seeds, make sure the berries are mature. Remove the orange-red aril around the seeds and plant them immediately. Bittersweet seeds need about three months of cold temperatures to break dormancy and germinate. Planting seeds in a coldframe or other protected location outdoors often is the most convenient way to give them to the required cold treatment.
Alternatively, bittersweet can be produced from cuttings of plants whose sex is known. If the parent plant produced berries, it is female. Plants that have never produced berries most likely are males, although they could be female plants that lack the proper environment for flowering. Cuttings of bittersweet are fairly easy to root either as softwood cuttings in summer or dormant cuttings in winter.
Cuttings taken in early to midsummer should be treated with a root-promoting hormone (e.g. IBA) and placed in conditions of high humidity. Sterile sand, vermiculite or a potting mix blend make ideal rooting media. Covering the cuttings with a plastic bag will help prevent desiccation; placing the cuttings in a lightly shaded area will help prevent temperatures under the bag from becoming too warm. The plastic bag should be removed as soon as cuttings have rooted. The latter can be determined by pulling lightly on the cuttings to see if their roots are holding.
There is a fine line between an aggressive but attractive ornamental plant and an invasive weed. Bittersweet skirts that boundary. For gardeners who want fall color from berries and a plant that attracts birds, bittersweet merits consideration.
REVISED: February 21, 2017