Chicago Botanic Garden


Chicago Botanic Garden
Plant Conservation
Invasive plants in the Chicago Region

The process involved members of the senior staff and representatives from the horticulture, collections, conservation science and ornamental plant development departments. The team reviewed ten invasive plant lists from the upper Midwest and through a series of discussions came to consensus on a list of plant species that we believe are invasive, or likely to become invasive, in the Chicago region. Our list is dynamic and reviewed annually.

Kayri Havens, Ph.D. Medard and Elizabeth Welch Director of the Institute for Plant Conservation Chicago Botanic Garden

Invasive Plant List used by Chicago Botanic Garden

  1. IL ALA, WI ALA, IN ALA:  American Lands Alliance/Faith Campbell, Worst invasive plant species in the conterminous United States (1999), Lists for Illinois, Wisconsin, and Indiana respectively
  2. MWRPTF:  Midwest Rare Plant Task Force Invasive Species Team List (1999)
  3. IL DNR:  Illinois Department of Natural Resources, 25 weeds that pose the greatest threat to Illinois forests (1994)
  4. INPS:  Illinois Native Plant Society, list of 60 worst invasive plant species in Illinois (2000)
  5. INPAWS:  Indiana Native Plant and Wildflower Society, 40 worst weeds in Indiana (2000)
  6. WI DNR:  Wisconsin Department of Natural Resources, 25 introduced species to avoid planting (1998)
  7. Midewin:  Midewin National Tallgrass Prairie list of invasive species, *=existing problem, W=watch list
  8. USFS:  US Forest Service Eastern Region, Category 1 invasive plants (highly invasive non-native plants which invade natural habitats and replace native species) and Category 2 (moderately invasive plants)
When plants are introduced to a new location, either intentionally or accidentally, they can spread prolifically, out-compete native species for resources, and eventually even dominate the landscape.  Biologists are studying the mechanisms underlying a taxon’s ability to become invasive, but for now it is still difficult to predict whether or not a species will become invasive in a new habitat.  Some factors common to many invasive plants include:
  • Escape from natural enemies
  • Rapid growth and early maturity
  • Production of many seeds
  • Ability to reproduce vegetatively
  • Seeds that are dispersed widely (such as by birds or wind) and seeds that germinate quickly (do not have long dormancies)
  • Apomictic seed production (production of seed asexually)
What the Chicago Botanic Garden is doing to help
overcome invasive species:
The Chicago Botanic Garden is well known for its diverse and beautiful horticultural displays.  One of its goals has been to develop the most diverse horticultural plant collection in the Midwest.  To build its collection, the Garden has been an active participant in exploration trips to countries in Asia and Europe, as well as other parts of the United States, to bring back new plants with horticultural merit.  The Ornamental Plant Development department has programs in plant breeding, plant evaluation, and plant introduction with goals of developing, selecting, recommending, and introducing the best horticultural plants for the Chicago region to the nursery industry. In recent years the Garden has become more concerned about invasive plants. Nearly one-third of the Chicago Botanic Garden's 385 acres is devoted to Native Habitat areas. There, Garden staff are actively implementing and conducting research on management protocols that remove invasive plants and help prevent their recolonization. The Chicago Botanic Garden is now evaluating many of the plants collected abroad through the Plant Exploration program before they enter the collection. Species that show signs of weediness in the evaluation period (four years for herbaceous plants, seven to ten years for woody plants) are destroyed. The Gardens Collection Policy states that any plant which has the potential to threaten the genetic diversity of local native populations, has overly aggressive behavior (weedy), or the ability to introduce pests or diseases will be screened and evaluated before being accepted into the Collection.

Information provided by Julia Zanieski Plant Information Chicago Botanic Garden.