The nursery and landscape industry is facing the loss of some of its most important landscape shrub crops, such as japanese barberry and winged euonymus, because of their invasive tendencies. Consumer awareness of invasiveness has reduced sales of profitable species (McCoy, 2011) and plant bans have eliminated the crops in some areas. Both japanese barberry and winged euonymus have been banned in Massachusetts (Massachusetts Department of Agricultural Resources, 2005) and New Hampshire (New Hampshire, 2004), and two counties in Long Island, NY, have legislation in place that will ban these species in 2016 (Cornell University Cooperative Extension, 2009a, 2009b). The Connecticut Nursery and Landscape Association (CNLA) enacted a voluntary ban on high-fruiting japanese barberry cultivars in 2010 (CNLA, 2010). Major wholesale nursery producers in Connecticut indicate that sales of japanese barberry and euonymus are down as much as 60% (M. Sellew, personal communication).
A widely recognized solution to the loss of invasive shrubs is the increased use of native shrubs for landscaping. A survey of 270 members of the CNLA found that growers strongly favored the promotion of native plants as a solution to the invasive plant problem (Gagliardi and Brand, 2007). Japanese barberry and winged euonymus are among the most popular landscape shrubs because they are highly adaptable to variable landscapes and perform well under difficult growing conditions such as parking lot island plantings. If native plants are going to be successful as replacements for invasive species, it is critical that they be well adapted to challenging landscape sites. The majority of commercial landscape situations involve relatively harsh conditions, which might include reflected light, high temperatures, inadequate water supply, infertile soil, road salt, and pedestrian pressure. One of the issues associated with native shrubs has been their blind recommendation without knowing landscape suitability and the false notion that all native plants are well suited for landscape purposes. Failed attempts in using native shrubs to replace invasive species may result in future reluctance of homeowners, landscapers, and growers to embrace native species as alternatives to invasive species.
Some native plants are already widely used for landscaping and have proven themselves to be adapted to commercial landscape situations. The nursery industry needs a substantially broadened palette of versatile and adaptable native plants to meet the growing desire of landscapers and consumers to use native plants in landscaping. Native plants such as american filbert, buttonbush, northern bush honeysuckle, steeplebush, sweet fern, and sweet gale exhibit wide adaptability in natural settings (Dirr, 2011; Hightshoe, 1988), making them prime candidates for development as native landscape plant alternatives for difficult sites. Much of the native plant evaluation work done to date has been more empirical than quantitative, where a single plant is installed and observed over time. If this individual fails, the cause of failure, whether due to poor planting site, weak initial root system, damage from people or animals, or something else, is usually unknown. The objective of this study was to determine whether these six native shrubs are well adapted to landscape use. The identification of well-adapted native plants will enable the nursery industry to produce plants that will be successful in landscaping and profitable over time.
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