24 ἀ e deeper and deflected nature of the root sys- tem in finished SM liners (Table 1) li kely explains the abundance of root defects at the liner position in both 9.5 L container types (Table 7). Trees did not grow out of that condition created in t he propaga- tion liner in either larger container type. ἀ e lack of root deflection in EP propagation containers (Table 1) was responsible for the small imprint at that posi- tion and far greater number of roots reaching the side wa lls (p eriphery) o f t he PC 9.5 L co ntainer (Table 7; Figure 2). Root tips in EP liners remained in the horizontal position near the liner periph- ery without deflection, which positioned them for growing horizontally into the PC co ntainer. How- ever, in SC 9.5 L co ntainers, root defects on trees propagated in EP mimic ked those of t rees propa- gated in S M liners, suggesting that the benefits of growing a high-quality root system in the liner (i.e., in EP) di sappeared when shiſting into a l arger SC container. ἀi s was attributable to the largest roots from b oth p ropagation co ntainer t ypes g rowing downward from the bottom of the liner to the bot- tom of the 3.8 L and 9.5 L SC containers (Table 4). Once at the bottom, roots deflected and continued to grow along the bottom forming an imprint that remained with the tree in the 9.5 L container (Table 6; Figure 2) a s others have found for smaller con- tainers (Selby and Seaby 1982). A ggressive growth at the bottom of the 3.8 L SC containers appeared to inhibit initiation or growth of horizontal roots closer to the substrate surface, and resulted in a vertically oriented and circling root system on fin- ished 9.5 L SC trees (Figure 2). Deflection of struc- tural roots downward in the container forced them to g row p arallel a nd cr oss o ne a nother dir ectly under the trunk (Table 7) causing constrictions and inclusions that can restrict p assage of substances through vascular tissue (Lindström and Rune 1999). In contrast to SC containers, growing trees in PC produced a root system with a more horizontal than vertical orientation (Table 6; Figure 2). ἀi s has not been reported before for containers of this large size. Vertical root growth was discouraged by the elevated and highly porous bottom that stopped elongation of roots that penetrated it. Vertical roots died back (brown root tips growing through the bottom were visible) once exposed to the dry air beneath the ele- vated bottom which effectively root pruned t hem. Air pruning at the bottom appeared similar to that of ©2014 International Society of Arboriculture Gilman and Paz: Container Production Strategies at least one other container that prunes with air (Gil- man et a l. 2010). I nhibition of des cending vertical roots induced formation of new roots or growth on existing roots close to the soil surface, and promoted growth in h orizontal-oriented r oots di stributed throughout t he r oot b all p rofile. ἀ e t remendous (49-fold, Table 6) increase in horizontal growth in 9.5 L PC was caused by a combination of 1) continued growth on existing non-deflected horizontal roots in the 3.8 L PC containers (Table 5), and 2) initiation of new horizontal roots at the flare in the 9.5 L container (Table 6). N either of these phenomena occurred in SC containers. Mahogany trees with horizontal-ori- ented lateral roots close to the top surface of the root ball develop a different root system in the landscape than those with vertical and circling roots, leading to b etter a nchorage (G ilman a nd Harchick 2014). CONCLUSION Mahogany root systems in a container can be g rown w ith a ttributes a ssociated w ith well-anchored l andscape t rees (i .e., w ith straight r oots, s ome c lose t o t he s urface). Acknowledgments. ἀ anks to the Horticulture Research Institute, GreatSouthernTreeConference.org (which included funding from the container manufacturers of the tested and other containers), and Quintessence Nursery for partial funding. LITERATURE CITED Anonymous. 1998. Flo rida G rades a nd S tandards f or N ursery Plants. Florida Department of Agriculture and Consumer Ser- vices, Gainesville, Florida, U.S. Arnold, M.A., and G.V. McDonald. 2006. Shrub rose responses to production in S mart Pots a nd conventional co ntainers u sing two contrasting substrates. Subtropical Plant Science Journal of the Rio Grande Valley Horticulture Society 58:1–4. Balisky, A.C., P. Salonius, C. Walli, and D. Brinkman. 1995. Seedling roots and forest floor: Misplaced and neglected aspects of Brit- ish Columbia’s reforestation effort. Forestry Chronicle 71:59–65. Burdett, A.N. 1978. C ontrol of root morphogenesis for improved stability in co ntainer-grown lodgepole pine. Canadian Journal of Forest Research 8:483–486. Coutts, M.P ., C. W alker, a nd A.C. B urnand. 1990. Effects o f establishment method on root form of lodgepole pine and Sitka spruce and on the production of adventitious roots. Forestry 63:143–159. Gilman, E.F., and C. Harchick. 2014. C ontainer design influences Swietenia mahagoni root attributes and anchorage aſter land- scape planting. Arboriculture & Urban Forestry 40:27–35. Gilman, E.F., and C. W iese. 2012. R oot pruning at planting and planting depth in the nursery impact root system morphology and anchorage. Arboriculture & Urban Forestry 38:232–239.
January 2014
| 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
