The Delaware Department of Agriculture published an excellent reference book entitled Mistaken Identity? Invasive Plants and their Native Look-alikes. If you haven't seen it be sure to check it out. This is definitely one piece of reference material that needs to be on your desk.
While some invasive plants are distinctive and easily recognized, many others are difficult to distinguish from one or more species of our native flora. For landowners, managers, and the general public, identifying confusing invasive plants can be extremely difficult. While many existing publications include identification tips, none present a complete side-by-side, illustrated comparison of the key characteristics needed to confirm identification of invasive plants that are often confused with similar native look-alikes. This guide fills a need for regional photographic guide to a broad selection of invasive plants that are often confused with similar native look-alikes.
The vast majority of invasive plant species established in the Mid-Atlantic are native to Asia and Eurasia. Since the climates of Europe and temperate Asia are similar to that of the northern United States, these species are well-suited for life in our region. Interestingly, while most of our invasive trees, shrubs, and vines originated in Asia, many of our herbaceous invasive plants originated in Europe.
Many of our invasives were first introduced as ornamental plants, usuallyby arboreta, botanical gardens, or less often, individuals. Woody invasive plants in particular were primarily the result of horticultural introductions. Other invasives, particularly grasses and vines, were introduced and spread by agronomists as potential livestock forage (Johnson Grass, Kudzu). Likewise, many shrubs and vines (Honeysuckles, Multiflora Rose) were widely promoted by state and federal wildlife agencies as cover and food sources for wildlife. A few introductions represent other miscellaneous attempts at economic stimulus (e.g. the introduction of White Mulberry as a host tree for silkworm moth caterpillars).
The second group of invasive introductions is those that were truly accidental in nature. Most of these involve herbaceous plants introduced by seed. An example cited in this guide is the introduction of Japanese Stiltgrass via plant material used as packing for porcelain shipments.Invasive species introductions have historically been somewhat preventable occurrences. The horticulture industry has grown more interested in stopping the importation and sale of invasive plants, although many are still widely available. State and federal agencies are now focused on invasive plant eradication, rather than introduction, reversing the past trend or searching for novel wildlife plants, and opting for largely natives. Increasing globalization, however, will undoubtedly lead to further spread of plant species worldwide, making an understanding of their ecology and control of utmost importance.