Oriental bittersweet (Celastrus orbiculatus) is a deciduous, woody, perennial vine native to parts of Asia. It was introduced as an attractive and hardy ornamental to the U.S. sometime between 100-200 years ago. It can now be found in many eastern states, but the area around Asheville, North Carolina might win the prize for today’s largest and most insidious bittersweet infestations, due to successful marketing by area nurseries in the early years of its introduction.
Oriental bittersweet is considered by many to be our region’s most problematic forest plant invader. This is because, like kudzu, it is a fast grower and will quickly overtake, strangle and topple trees; but worse than kuzdu, oriental bittersweet has an extremely high germination rate, even in low light conditions. This means that, unlike kudzu, it can grow successfully within the forest interior, and is not limited to roadways and forest edges. Its attractive, long-lasting red-orange berries have helped to facilitate the species’ successful spread because birds, crafty humans and ichibana devotees, alike, can’t resist carrying them around to new places. But bittersweet doesn’t just rely on its seed to ensure its survival; it will also re-sprout from its roots.
There is an American bittersweet species (Celatrus scandens), which can be differentiated from the invasive oriental bittersweet by the shape of the leaf and where the berries are found on the stem, but the American species is rare, so you are unlikely to see it in most places you suspect oriental bittersweet. The oriental species is known to hybridize with the american species, which further threatens the american species.