The 2012 ASHS Annual Conference

There is increased interest in using native plant alternatives to invasive species for landscaping. Invasive Japanese barberry (Berberis thunbergii) and winged euonymus (Euonymus alatus) are used extensively in landscaping since they perform well in challenging landscapes, such as parking plantings. Some ornamental Connecticut native shrubs for which little is known regarding landscape suitability include American filbert (Corylus americana), buttonbush (Cephalanthus occidentalis), sweet fern (Comptonia peregrina), sweet gale (Morella gale), northern bush honeysuckle (Diervilla lonicera) and hardhack (Spiraea tomentosa). These six species were evaluated for their landscape suitability in parking lot islands to determine which can serve as suitable replacements for barberry and euonymus. Japanese barberry and euonymus were included in the planting as controls. The experimental planting was installed in June 2010 and consisted of 6 replicated planting blocks each with 5 individual shrubs per species, for a total of 240 shrubs. At 15 months post planting, the barberry and euonymus controls had performed well. Sweet fern, sweet gale and buttonbush had performed as well as the invasive controls. American filbert and northern bush honeysuckle also performed well, but blocks with wetter soils did not perform as well as blocks with dry soils indicating that these two species are best used in well-drained sites. Hardhack did not perform as well as the invasive control or other native shrubs evaluated and cannot be recommended. While the flowers of hardhack provided ornamental interest, plant appearance was variable and powdery mildew was problematic. This study shows that native plants can be suitable alternatives to invasives and some may perform well in landscape situations that are different from the native environments in which they are found. Buttonbush and sweet gale occupy swampy or edge of water habitats, but were able to perform well in a much drier landscape situation. This work clearly demonstrates the need to evaluate a prospective native ornamental plant for adaptability outside its apparent environmental niche. Evaluation of the planting will continue to develop information about long-term performance.