Black Swallow-Wort Identification & Control Methods

The black swallow wort plant is a vine native to Europe that has become invasive in parts of the U.S. It was intentionally brought here as an ornamental vine but now wreaks havoc in many ecosystems. Learn how to identify this problematic vine and control methods to help eradicate it from your area.

Black swallow wort vine has been declared invasive in much of the Midwest and Northeast U.S. Check with your local extension office to find out if it is a problem in your area.

As with most invasive plants, the primary problem with black swallow wort is that it outcompetes native species. It does this in several ways, including by tolerating a variety of conditions. It grows in both sun and shade and tolerates a variety of soils.

Black swallow wort also spreads and reproduces prolifically. It spreads through both rhizomes and seeds, producing thousands of seeds for every square meter. Each seed produces up to four embryos. These strategies give it a major advantage over many native plants. The rhizomes spread and can help a plant cover a large area quickly.

As a vine, black swallow wort can form dense, low-growing mats. It can also grow up and around other plants and strangle them. This gives it one of its common names, “dog-strangling vine.” Another strategy the vine has for outcompeting native species is allelopathy, meaning that it produces chemicals that harm other plants in the area.

That black swallow wort can outcompete and literally smother native plants is a problem. Another major issue with this invasive plant is the harm it causes to the already beleaguered monarch butterfly.

Monarchs solely lay eggs on milkweed; black swallow wort is related to milkweed and resembles it. Studies have found that monarchs mistake it for