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David M. Czarnecki II, Amanda J. Hershberger, Carol D. Robacker, David G. Clark and Zhanao Deng

species status of L . camara has become the most significant barrier for growers and landscapers who are interested in producing or planting L . camara . The major determinant of the invasive potential of L . camara is its ability to produce viable

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Mohammed I. Fetouh, Abdul Kareem, Gary W. Knox, Sandra B. Wilson and Zhanao Deng

huge impact and meet the nursery and landscape industry’s need for plant materials, horticulturists have been searching for cultivars with reduced invasive potential ( Knox and Wilson, 2006 ; Trueblood et al., 2010 ; Wilson and Mecca, 2003 ; Wilson

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Janine R. Conklin and James C. Sellmer

among the present or previously popular cultivars employed in the green industry ( Lehrer and Brand, 2003 ). Few studies have addressed flower and seed yields along with other biologic traits in determining the invasive potential of cultivars for known

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Janine R. Conklin and James C. Sellmer

. Torrey Bot. Soc. 128 141 149 Westbrooks, R.G. 1998 Invasive plants, changing the landscape of America: Fact book. Federal Interagency Committee Mgt Noxious Exotic Weeds Washington, DC Wheeler, A.R. Starrett, M.C. 2001 Determining the invasive potential of

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W.C. Dunwell, D. Fare, M.A. Arnold, K. Tilt, G. Knox, W. Witte, P. Knight, M. Pooler, W. Klingeman, A. Niemiera, J. Ruter, T. Yeager, T. Ranney, R. Beeson, J. Lindstrom, E. Bush, A. Owings and M. Schnelle

The Southern Extension and Research Activities/Information Exchange Group-27 (SERA/IEG-27) is sponsored by the Southern Association of Agricultural Experiment Station Directors. Thirteen universities and the U.S. National Arboretum cooperate with official representatives from extension and research programs. The objective of the group is to identify, evaluate, select, and disseminate information on superior, environmentally sustainable, landscape plants for nursery crop production and landscape systems in the southeastern U.S. Plants are distributed to members responding to a request from cooperators for plant evaluation. Those who agree to cooperate are expected to grow the selected liner to landscape size, then transplant it in a landscape setting. The plant is rated for insect, disease, and cold damage, heat stress, growth rate, ornamental flowering and fruiting, fall color, commercial production potential, landscape potential, invasiveness potential, and insect disease transmission potential. Growth rate is evaluated annually by recording plant height and width. Initial bloom date is reported followed by bloom duration in days. Following evaluation, the group collectively and individually disseminates information gained from the plant evaluation system to a wide variety of audiences.

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Winston C. Dunwell

SERA-IEG-27, Southern Extension and Research Activities–Information Exchange Group–27, is sponsored by the Southern Association of Agricultural Experiment Station Directors. Thirteen states cooperate with Official Representatives from Extension and Research programs. The objective of the group is to identify, evaluate, select, and disseminate information on superior environmentally sustainable landscape plants for nursery crop production and landscape systems in the Southeast. Plants are distributed to those responding to a request for plant evaluation cooperation. Those that agree to cooperate are expected to grow a liner to landscape size, plant it in an landscape setting and evaluate the plant (numerically, a scale of 1–10 for insect damage, disease damage, cold damage, heat stress, growth rate, flower, fruit, fall color, production potential, landscape potential, invasive potential, and insect disease transmission potential, as well as plant height and width and time/duration of bloom). Following evaluation the group is to collectively and individually disseminate information gained from the plant evaluation system to a wide variety of audiences.

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Ryan N. Contreras and Luigi Meneghelli

Prunus laurocersaus L. (2n = 22x = 176), common cherrylaurel, is an evergreen shrub generally used as a hedge or screen. This species produces large drupes that are a nuisance when they drop on walkways or deposited by birds and also has escaped cultivation in parts of northwestern United States, which has raised concern about the invasive potential of common cherrylaurel. Therefore, a fruitless and sterile form of common cherrylaurel is desirable. As part of our efforts to develop sterile common cherrylaurel cultivars, we conducted two experiments to induce chromosome doubling using in vitro exposure of ‘Otto Luyken’ and ‘Schipkaensis’ cherrylaurel to oryzalin. For ‘Otto Luyken’ (Expt. 1), we tested the effects of treatment duration (1, 2, 14, or 28 days) and oryzalin concentration (0, 6.25, 12.5, 25, 50, 100, or 150 μm) applied in a liquid phase over explants. In Expt. 2, we treated ‘Schipkaensis’ cherrylaurel shoots with a single duration of 28 days and exposed explants to the same varying concentrations of oryzalin incorporated into the solidified medium. In Expt. 1, the 14-day treatment had reduced survival compared with 1- and 2-day treatments and there was still greater mortality in the 28-day treatment. Duration of the treatment affected mortality more than oryzalin concentration. Sixteen treatment combinations resulted in 44x plants. The percentage of 44x plants increased with concentration in the 1- and 2-day treatments up to 30% of treated shoots at 150 μm. Overall, the longer duration treatments in Expt. 1 were less efficient for inducing 44x plants. Expt. 2 was less effective for inducing homogenous 44x plants. It is unclear if this is due to treatment or cultivar differences but the highest concentration was 8% in the 6.25 μm treatment.

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Jonathan M. Lehrer, Mark H. Brand and Jessica D. Lubell

While japanese barberry (Berberis thunbergii DC.) is an acknowledged invasive plant naturalized throughout the eastern and northern U.S., the danger posed by its popular horticultural forms is unknown and controversial. This work analyzed the reproductive potential and seedling growth of four ornamental genotypes important to the nursery industry. Fruit and seed production was quantified in 2001, 2002, and 2003 for multiple landscape plants of B.t. var. atropurpurea, `Aurea', `Crimson Pygmy', and `Rose Glow'. The average number of seeds produced per landscape specimen ranged from lows of 75 and 90 for `Aurea' and `Crimson Pygmy' to 2968 for var. atropurpurea and 762 for `Rose Glow'. Seed production relative to canopy surface area for `Rose Glow' was similar to `Aurea' and `Crimson Pygmy' and all three cultivars were less prolific than var. atropurpurea in this regard. Cleaned and stratified seeds from var. atropurpurea, `Crimson Pygmy' and `Rose Glow' showed an average greenhouse germination rate of 70% to 75%, while `Aurea' yielded 46% germination. A subpopulation of seedlings from each genotype accession was grown further outdoors in containers for a full season to ascertain seedling vigor and development. The vigor of 1-year-old seedlings, as measured by dry weight of canopy growth, for progeny derived from `Aurea' (0.70 g) and `Crimson Pygmy' (0.93 g) was significantly less than var. atropurpurea (1.20 g) and `Rose Glow' (1.33 g). These results demonstrate that popular japanese barberry cultivars express disparate reproductive potential that, after further study, may be correlated with invasive potential. Some popular commercial cultivars may pose significantly less ecological risk than others.

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Kelly M. Oates, Thomas G. Ranney, Darren H. Touchell and Zenaida Viloria

invasive. Propagule pressure, including production of viable seeds, is an important aspect of invasion potential and has a consistent positive association with the establishment of self-sustaining populations ( Colautti et al., 2006 ). Reducing fertility by

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(p. 91) evaluated mature trees of norway maple and six norway maple varieties to study flower and seed productivity and to determine the invasive potential (via seed propagation) of each variety. ‘Columnare’, ‘Emerald Queen’, and the species produced