Because of the severe environmental and economic costs of invasive plants, organizations and individuals importing plants into new regions should evaluate plant introductions for their potential to escape cultivation and invade natural areas. Current weed risk assessment (WRA) models used in the United States are not precise enough to provide a definitive answer for woody taxa and have not yet been developed specifically for annuals and herbaceous perennials. We tested several WRA models to determine their effectiveness for the Chicago region and selected one for use in the invasive screening protocol at Chicago Botanic Garden that includes the use of regional invasive plant lists, commercial availability, WRA, and on-site evaluation of plants. By using this integrated approach, we have implemented a screening protocol that has increased our confidence in predicting invasiveness, is time and space efficient, and is user-friendly.

Additional index words: Alien plants, botanic garden, Chicago, evaluation, horticulture, invasive plants, weed risk assessment.

Abbreviations: CBG, Chicago Botanic Garden; NISC, National Invasive Species Council; WRA, weed risk assessment.