Invasive Vines in Indiana—Be On the Lookout!
Grapevines are native to Indiana woodlands, yet they are often controlled on lands managed for timber production to prevent the vines from shading out the trees’ leaves, damaging branches, or bringing down trees. Grapes have benefits, as well, providing food and nesting material for many species of native wildlife. There are a growing number of invasive, non-native vines in Indiana, however, which have similar impacts on tree growth and survival, without the benefits of providing high-quality food for wildlife. Learning how to identify these invasive plant species will help you to control them early before they become a problem on your land.
Japanese honeysuckle (Lonicera japonica) is one of the most widespread invasive vines in the state, occurring in all Indiana counties. Widely planted for its pretty and fragrant flowers, this ornamental species has become a problematic pest. Research has shown that native trees have decreased growth when they are infested with Japanese honeysuckle, and young trees can be killed by girdling when honeysuckle vines twist tightly around their stems and trunks. Japanese honeysuckle has a competitive advantage over native plant species, because it is browsed less by deer and resprouts vigorously when browsed. It also holds its leaves longer than native plants giving it a longer growing season. Japanese honeysuckle can be identified by its opposite, oval leaves, fragrant pairs of white or yellow flowers, and purple to black berries.
Kudzu (Pueraria montana var. lobata), known as “The Vine That Ate the South”, has moved northward from the southern U.S. in recent years, and is now present in most counties in southern Indiana, as well as a few in the northern part of the state. Kudzu grows extremely quickly (as much 1 foot per day) and vigorously, forming a blanket over both trees and the ground. Dense kudzu thickets are difficult to control, so early detection of this species is critical. Kudzu leaves are composed of three leaflets that may be entire or lobed, with hairy leaf margins. Its flowers are purple, fragrant, and hang down in clusters. Kudzu fruits are brown, hairy pods.
Oriental or Asian bittersweet (Celastrus orbiculatus) was introduced as an ornamental plant and is still widely used in decorative fall wreaths because of its abundant, bright-colored fruits. This species has been reported in 44 counties throughout the state. Asian bittersweet is tolerant of a wide range of habitats, infesting forests, woodlands, fields, hedgerows, and coastal areas. It can be identified by its alternate, glossy leaves, which are round in shape with an abruptly pointing tip and shallow teeth along the leaf margins. The fruits are distinctive round capsules that are green in summer, and yellow to orange in fall. When they are mature, the capsules split open, revealing a red-orange fruit inside. American bittersweet, a native vine, is very similar in appearance to the invasive bittersweet, but can be distinguished by having flower and fruit clusters at the end of the vine, rather than all along the stem as on the invasive bittersweet. American bittersweet leaves are often longer and less rounded, as well. Make sure you correctly identify which bittersweet you have before beginning any control efforts.
Two newer invaders in our region are the annual vines, Japanese hop (Humulus japonicus) and mile-a-minute (Polygonum perfoliatum). Japanese hop primarily invades riparian areas, forming deep, dense mats over the ground, shrubs, and small trees. It has been reported in 15 Indiana counties and can be identified by its rough-textured, palmate leaves with five to seven lobes, and rough-textured stems with downward pointing prickles that irritate the skin. Mile-a-minute, as its name suggests, grows rapidly and kills plants by blocking light from reaching plants beneath it. Mile-a-minute leaves have a distinctive triangular shape. The plant can also be identified by cup-shaped leafy structures surrounding the stem at its nodes and barbs on the stem. Mile-a-minute is present in eastern Ohio but has not yet been reported in Indiana.
If you see these new species in Indiana, you can report them through the Great Lakes Early Detection Network website (www.gledn.org). Reporting an invasive plant just takes a few minutes but will help your neighbors by letting them know what’s nearby. For more information on invasive plants, visit the Midwest Invasive Plant Network (MIPN) at www.mipn.org. Control information for the most common invasive plants in our region can be found in the MIPN Control Database at http://mipncontroldatabase.wisc.edu.
Kate Howe is the Midwest Invasive Plant Network Coordinator at Purdue University.