Arboriculture & Urban Forestry 32(6): November 2006 Arboriculture & Urban Forestry 2006. 32(6):305–311. 305 Effects of Planting Depth on Landscape Tree Survival and Girdling Root Formation Christina Wells, Karen Townsend, Judy Caldwell, Donald Ham, E. Thomas Smiley, and Michael Sherwood Abstract. Landscape trees are frequently planted with their root collars below grade, a practice that may predispose them to transplant failure and girdling root formation. The objective of the present research was to examine the effect of planting depth on the health, survival, and root development of two popular landscape trees, red maple (Acer rubrum) and Yoshino cherry (Prunus × yedoensis). Trees were transplanted with their root flares at grade, 15 cm (6 in) below grade, or 31 cm (12 in) below grade. Deep planting reduced the survival of Yoshino cherries: 2 years after transplant, 50% of the 15 cm (6 in) and 31 cm (12 in) deep-planted cherries had died, whereas all the cherries planted at grade had survived. Survival of maples was not affected by planting depth. Deep planting also influenced the development of girdling roots. Three years after transplant, maples planted at grade had 14% of their trunk circumference encircled by girdling or potentially girdling roots; this number rose to 48% and 71% for 15 cm (6 in) and 31 cm (12 in) deep-planted maples, respectively. There were no treatment-related differences in girdling root development in the cherries. These results are consistent with arborists’ observations that deep planting is a significant source of stress in landscape trees. Key Words. Acer rubrum; girdling root; planting depth; Prunus × yedoensis. Root collar burial is remarkably common in landscape trees. In a 1991 survey, 93% of professionally planted trees had root collars obscured by soil or mulch, and the extent of this deep planting was seldom less than 2 in (Smiley and Booth 2000). In a survey conducted by the University of Rhode Island’s Sustainable Landscape Arboretum, buried root col- lars were present in over 75% of the nursery-grown trees examined, and the depth of burial ranged from 3 to 12 in (Maynard 1995). Root collar burial at transplant positions much of the tree’s root system in deeper soil layers where access to water, nu- trients, and oxygen may be restricted. Anecdotal evidence suggests that root collar burial predisposes trees to transplant failure and girdling root development, but little scientific re- search has been performed to evaluate these claims. A study on pygmy date palm suggests that deep planting reduces growth and survival in this species (Broschat 1995), and similar results have been reported for willow oak (Quercus phellos) and white pine (Pinus strobus; Smiley and Booth 2000). Recent work by Gilman and Grabosky (2004) indi- cates that deep-planted trees may fail to intercept water from light rainfall events soon after transplant, leading to signifi- cant water stress. Nonetheless, the general significance of deep planting as a source of landscape tree stress remains open for debate. The objective of the present research was to examine the effect of planting depth on the health, survival, and root de- velopment of two popular landscape trees, red maple (Acer rubrum) and Yoshino cherry (Prunus × yedoensis). A com- bination of above- and below-ground measurements was used to characterize tree responses to root collar burial. METHODS Experimental Planting The experiment was performed in a half-acre open field in the Roland Schoenike Arboretum in Clemson, South Carolina, U.S. The site exhibited a 10% slope. The soil was an eroded Cecil sandy loam with a pH of 5.5, a cation exchange capac- ity of 3.9 meq/100 g, and sufficient levels of all mineral nutrients except phosphorus, which was present at 5.6 kg/ha (5 lb/ac). In December 1996, 2 in caliper balled-and-burlapped ‘Oc- tober Glory’ red maples (Acer rubrum) and Yoshino cherries (Prunus × yedoensis) were obtained from a local nursery. The trees had been grown from cuttings on their own root stock and were dug immediately before transplant. Thirty trees of each species were planted in a randomized complete block design consisting of ten replicate blocks within which the two species and three planting depth treatments were randomly arranged. Planting depths included control (planted with the ©2006 International Society of Arboriculture
November 2006
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
