Invasions of nonnative plants into southern forests continue to go largely unchecked and only partially monitored. Small forest openings, forest road right-of-ways, and areas under and beside forest canopies are often occupied by invasive nonnative plants. These infestations increasingly erode forest productivity, hindering forest use and management activities, degrading diversity and wildlife habitat. Often called nonnative, exotic, nonindigenous, alien, or noxious weeds, nonnative invasive plants occur as trees, shrubs, vines, grasses, ferns, and forbs. Some have been introduced into this country accidentally, but most were brought here as ornamentals or for livestock forage. These robust plants arrived without their natural predators of insects, diseases, and animals that tend to keep native plants in natural balance. Many have hybridized and undergone plant breeding to become more aggressive, predator resistant and resilient, drought tolerant, and cold hardy. Now, they increase across the landscape with little opposition beyond the control and reclamation measures applied by landowners, managers, and agencies on individual land holdings. An increased awareness of the threat has resulted in growing networks of concerned individuals, agencies, governments, and companies aimed at stopping plant invasions across landscapes and restoring formerly infested lands.
The objective of this book is to provide information on accurate identification of 56 plants or groups (like the many invasive roses) that are aggressively invading forests of the 13 Southern States at alarming rates. It also lists other nonnative invasive plants that are of growing concern. A companion booklet, “A Management Guide for Invasive Plants of Southern Forests,” explains control recommendations, selective application procedures, and prevention measures for these and other plant invaders. The text and photographs for 33 species were originally developed for the 2003 edition to assist in the first regionwide survey and monitoring of these invading species. Survey work was conducted by the Forest Service, U.S. Department of Agriculture, Forest Inventory and Analysis Research Work Unit of the Southern Research Station in collaboration with State forest management agencies. The four-number survey codes are given for these species as well as the international plant codes for all species when available (see opposite page). The latest data for this ongoing survey can be viewed and downloaded at http://srsfia2.fs.fed.us/data_center/index.shtml.
Accurate identification of nonnative invasive plants is critical for recognition of new entries and positive control of existing infestations. Many invasive species have native and nonnative plants that closely resemble them and most have been commercially bred to yield many varieties with varying traits. A section is included for each invasive species giving traits to distinguish them from their “look-a-likes.” Use these traits to safeguard valuable native plants and for directing controls toward the appropriate invasive plant species.
