Identifying invasive plants is not always easy. But winter brings helpful clues to the branches of some habitat-altering vines and shrubs: berries. At least, that’s what most of us call them (botanically, these fruits may be pomes, drupes, or arils). With fruit persisting from fall into deep winter, many of these plants are carried further afield by birds who feed on them in the lean season. Some of these invasive plants have become so problematic that individual states have banned their sale. Despite that, some persevere in public plantings and (perversely) in botanical gardens, where they now seem like relics of an age of innocence, when exotic plant collections were tended without a thought as to how they might change the broader landscape and the biological livelihood of a place to which they are native.
In time for a horticultural New Year’s resolution, here are eight bad berries: Don’t plant these invasive plants, and if you have the means, control or remove them.
Photography by Marie Viljoen.
1. Privet
Usually seen in the form of a tidily clipped privacy-hedge, privet is the common name of several species of Ligustrum, but often refers to Ligustrum sinense, or Chinese privet, introduced to the United States from East Asia. Because its fruits (drupes, botanically) are relished by birds, the shrubs have escaped cultivation and these invasive plants have spread—especially in the Southern US and in the Northeast, where they form dense thickets that crowd out native plants. If you must keep a privet hedge, shear off its fruit in late fall or early winter.
2. Asian Bittersweet
As invasive plants go, these vines can be vexing, because the native and invasive species of bittersweet look very similar. The American species, Celastrus scandens, bears its berry-like arils only in terminal clusters (meaning at the end of each branch), whereas the fruit of Asian bittersweet (C. orbiculata) appears in leaf axils, all along each branch. Bittersweet climbs trees and shrubs, adding so much weight that it can break them. As it twines, it girdles trunks and branches.
3. Burning Bush (or Winged Euonymus)
You can see why it is loved: In fall, the leaves of burning bush (also known as winged Euonymous because of the thin ridges on its branches) blaze scarlet. When its arils pop open, they reveal vividly orange seeds, which birds eat happily. Euonymous alatus has spread widely into woodlands where it alters their ecology by displacing native plants. Do not plant it, do not sell it, and if you remove it, choose a native shrub like winged sumac (Rhus copallinum) to replace it.
4. Jetbead
Their white flowers are lovely in mid-spring, resembling mock orange, but black jetbead shrubs create a dense understory in woodlands, preventing the development of native seedlings, and—we’ll say it again—altering the local ecology. The glossy fruit are drupes held in clusters of two to four, and resemble minimalist blackberries.