![]() ![]() High branches that could not be reached on the ground were accessed using climbing equipment or ladders, and low branches were accessed from the ground by hand. Initially, four entire lateral branches off of the main stem of each cultivar were randomly selected for use over the study period and were marked at various heights of the canopy and from each cardinal direction to obtain a consistent estimate of flower and seed production throughout the tree. To characterize flower and seed production of the test plants (two to three plants/cultivar), several different data collection techniques were used. This is the first report in which norway maple cultivars have been evaluated using seed productivity to determine each cultivars invasive potential.įlower and seed production characterization. The purpose of this study was to determine the flower and seed productivity of the norway maple and its cultivars. With any cultivar evaluation, the process begins with defining flower and seed productivity. ![]() The replacements may include reintroducing older, less prolific cultivars that have been replaced by new cultivars. The immediate value of cultivar evaluation for seed production is the ability to advise the green industry of problem cultivars and possible replacements ( Wheeler and Starrett, 2001). Of the studies reported, all have focused on shrub ( Anisko and Im, 2001 Knox and Wilson, 2006 Lehrer et al., 2006 Lovinger and Anisko, 2004 Wilson et al., 2004a, 2004b), perennial grasses ( Meyer and Tchida, 1999), or herbaceous species ( Wilson and Mecca, 2003). Few studies have addressed flower and seed yields along with other biologic traits in determining the invasive potential of cultivars for known invasive species. It is logical to assume that less invasive or noninvasive cultivars of the invasive species may exist among the present or previously popular cultivars employed in the green industry ( Lehrer and Brand, 2003). Ecological researchers have reported that these affects on a forest community alter its structure by decreasing native species abundance, diversity ( Munger, 2003), and richness ( Martin, 1999 Webb et al., 2001 Wyckoff and Webb, 1996). Based on observations, the norway maple produces high quantities of seed, shade-tolerant seedlings, and dense canopies that further reduce light and moisture reaching the understory ( Gresham, 2000 Randall, 1996). Norway maple is one species that has been identified as potentially invasive to natural areas ( Munger, 2003 Randall and Marinelli, 1996 Swearingen et al., 2002 Webb and Kaunzinger, 1993 Webb et al., 2001 Wyckoff and Webb, 1996). It is generally understood that the larger the mature plant, the higher the yield ( Dieringer, 1991 Ollerton and Lack, 1998). Heavy flower production is required on the plant to yield high seed quantities ( Augspurger, 1983). One way that invasive plants displace natives and reduce biodiversity of forest ecosystems is by producing many seeds that are capable of germination ( Lehrer and Brand, 2003). In contrast, ‘Crimson King’, ‘Globosum’, ‘Faasen's Black’, and ‘Rubrum’ were relatively low in seed yield, which make them suitable alternatives for landscape use where invasiveness is a concern to surrounding communities. ![]() ‘Columnare’, ‘Emerald Queen’, and the species produced many seeds, which suggest that these plants may be problematic in landscapes that adjoin natural areas. For this study, it was observed that norway maple cultivars differed in annual flower and seed yield and that production varied from year to year. Flower and seed yield data were collected each year and were used to estimate whether differences existed among cultivars and if variation in these traits occurred from year to year. Mature specimens of the norway maple ( Acer platanoides) and cultivars Columnare, Crimson King, Emerald Queen, Faasen's Black, Globosum, and Rubrum were evaluated over a 3-year period to determine flower and seed production and to understand their invasive potential using seed yields. ![]()
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