A Regional Scheme for Foiling Non-Native Plant "Escapes"

Trees and shrubs native to other parts of the world have long spruced up U.S. gardens and landscapes. But problems arise when some of these plants escape cultivation to become weeds or invade natural plant communities.

That's why Agricultural Research Service horticulturalist Mark Widrlechner and colleagues are retooling a strategy for assessing the risk of such escapes across North America into something more suited for a specific region.

This work at the ARS North Central Plant Introduction Station in Ames, Iowa, has produced new models geared toward improving plant-escape predictions. The models integrate life-history traits of woody plants found in the north-central United States with climatic and geographic risk analysis.

Widrlechner's team collected data on 100 non-native landscape trees and shrubs grown in Iowa, tested approaches for predicting their escape abilities, and then compared the predictions with escape histories.

The scientists modified an existing decision tree for assessing the risk of non-native woody plants escaping anywhere in North America by including regionally important traits. They then designed a new decision tree featuring a geographic-risk factor based on the plants' native distributions and selected biological traits.

Few intentionally introduced species escape cultivation, and even fewer become pests. But effective predictive models can reduce time and costs associated with quarantine programs designed to spot problem plants. Widrlechner stressed that all related models and strategies should be augmented with long-term monitoring of sites that could be a foothold for newly naturalizing woody plants.

This study incorporated knowledge about regional adaptation of trees and shrubs gained through the NC7 Regional Ornamental Plant Trials. This program, which has evaluated more than 620 accessions of woody landscape plants under a wide range of environments, is marking its 50th year. It is funded by the U.S. Department of Agriculture (USDA) and 12 Agricultural Experiment Stations of the North Central Region.

Details of the study and the new models were published recently in the Journal of Environmental Horticulture.

ARS is the USDA's chief scientific research agency.