Development and Evaluation of Landscape Plant Cultivars with Reduced Fertility to Minimize Potential Invasiveness1

While only a small portion of introduced species naturalize, and even fewer become invasive, those that do may alter ecosystems and disrupt natural plant communities. Recognizing that many non-native landscape plants are valuable commodities that provide important ecosystem services, enhance property values, and improve our quality of life, there is strong justification for developing cultivars with low reproductive fertility to prevent further distribution. This report reviews approaches for developing and evaluating low-fertility landscape cultivars to minimize self-sowing, weediness, range expansion, and potential invasiveness with recommended approaches, guidelines, and policy. Specific conclusions and recommendations include: Selecting and developing cultivars with reduced fertility is a viable approach for maintaining economic, environmental, and aesthetic benefits of important landscape crops while minimizing potential invasiveness. A ≥ 98% reduction in fertility, compared to fertile controls, is an achievable and practical criterion for accepting low-fertility cultivars as alternatives to potentially invasive, sexually reproducing plants. Regulations of potentially invasive plants should include exclusions and provisions to allow for the continued production of cultivars with documented low reproductive fertility.