16 Gilman: Pruning Acer rubrum at Planting Impacts Structure and Growth vival, and it was therefore assumed foresters had no need to prune to compensate for root loss when trees were dug from a field nursery. As a sign of change in the profession, the International Society of Arboriculture’s Best Management Practices (Wat- son 2014) states that trees can be pruned at planting to develop strong structure and presents a method (Figure 1) similar to that tested in the current study. Reducing growth rate on large branches in young trees prepares branches in the lower 5 m of the trunk and crown for their eventual removal, which is typically necessary for clearance in urban and suburban streets and other locales (Kristof- fersen et al. 2010). Pruning to reduce the aspect ratio by slowing their growth rate keeps branches small, causing only a negligible pruning wound and little trunk dysfunction when they require removal (Eisner et al. 2002). Moreover, branches with a small aspect ratio are well attached to the trunk (Gilman 2003; Kane et al. 2008). In addi- tion, slowing growth on large, upright-oriented branches in the lower 5 m of the trunk is likely to reduce development of the somewhat-weaker upright tree structure (Miesbauer et al. 2014). Upright branches can also suppress the leader by shading it from one side, and both can become long with poor taper. Kristoffersen et al. (2010) also advises pruning at or soon after plant- ing to reduce growth rate on these large low branches to improve subsequent tree structure and health following their removal for clearance. CONCLUSION Other than a small but significant 8% reduction (5 mm) in trunk diameter growth (but no impact on height), there appear to be no downsides to pruning the largest branches at planting by reducing their length with reduction or heading cuts, thus suppressing their growth. The reduc- tion in aspect ratio on pruned branches shiſted the largest branches to higher in the crown. This will provide for better clearance and will result in small pruning wounds due to a reduction in relative branch diameter in the lower portion of the trunk. Debris requiring disposal should be reduced compared to trees not pruned at planting. Acknowledgments. Thank you to the TREE Fund and Greatsoutherntreecon- fererence.org for partial funding. LITERATURE CITED Anonymous. 1998. Florida Grades and Standards for Nursery Plants. Florida Department of Agriculture, Tallahassee, Florida. Bredenkamp, B.V., F.S. Malan, and W.E. Conradie. 1980. Some effects of pruning on growth and timber quality of Eucalyptus grandis in Zululand. South African Forestry Journal 114:29–34. Chandler, C.K. 1990. Comparison of pruned and unpruned pear seedlings for survival and growth. HortScience 25:123. Downer, A.J., M. Shaw, and D. Pittenger. 1994. The effect of prun- ing on branch growth in two oak species. HortScience 29:550, Abstract #815. Duryea, M.L., and S.K. Omi. 1987. Top pruning Douglas-fir seed- lings: Morphology, physiology, and field performance. Cana- dian Journal of Forest Research 17:1371–1378. Eisner, N., E.F. Gilman, and J. Grabosky. 2002. Branch morphology impacts compartmentalization of pruning wounds. Journal of Arboriculture 28:99–105. Elfving, D.C., and C.G. Forshey. 1976. Growth and fruiting responses of vigorous apple branches to pruning and branch orientation treatments. Journal of American Society for Horti- culture Science 101:290–293. Evans, P.S., and J.E. Klett. 1984. The effects of dormant pruning treatments on leaf, shoot, and root production from bare-root Malus sargentii. Journal of Arboriculture 10:298–302. Evans, P.S., and J.E. Klett. 1985. The effects of dormant branch thin- ning on total leaf, shoot, and root production from bare-root Prunus cerasifera ‘Newport’. Journal of Arboriculture 11:149–151. Fordham, R. 1972. Observations on the growth of roots and shoots of tea (Camellia sinensis L.) in southern Malawi. Journal of Hor- ticultural Science 47:221–229. Forshey, C.G., D.C. Elfving, and R.L. Stebbins. 1992. Training and pruning apple and pear trees. American Society for Horticul- ture Science. Alexandria, Virginia. Fumey, D., P. Lauri, Y. Guedon, C. Godin, and E. Costes. 2011. How young trees cope with removal of whole or parts of shoots: An analysis of local and distant responses to pruning in 1-year-old apple (Malus × domestica; Rosaceae) trees. American Journal of Botany 98:1737–1751. Funk, D.T. 1979. Stem form response to repeated pruning of young black walnut trees. Canadian Journal of Forest Research 9:114–116. Gilman, E.F. 2003. Branch to stem ratio affects strength of attach- ment. Journal of Arboriculture 29:291–294. Gilman, E.F., and J. Grabosky. 2009. Growth partitioning three years Arboriculture & Urban Forestry 35:281–286. Gilman, E.F., and S. Lilly. 2008. Best Management Practices: Pruning, second edition. International Society of Arboriculture, Cham- paign, Illinois, U.S. Gilman, E.F., P. Anderson, and C. Harchick. 2006. Pruning low branches of live oak (Quercus virginiana Mill.) cultivars and seedlings during nursery production: Balancing growth and efficiency. Journal of Environmental Horticulture 24:201–206. ©2015 International Society of Arboriculture following structural pruning of Quercus virginiana.
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