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Research ArticleArticles

Container Production Strategies Influence Root Ball Morphology

Edward F. Gilman and Maria Paz
Arboriculture & Urban Forestry (AUF) January 2014, 40 (1) 16-26; DOI: https://doi.org/10.48044/jauf.2014.002
Edward F. Gilman
Edward F. Gilman (corresponding author), Environmental Horticulture Department, University of Florida, Gainesville, Florida, U.S.,
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Maria Paz
Maria Paz, Environmental Horticulture Department, University of Florida, Gainesville, Florida, U.S.
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Abstract

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Poor anchorage and delayed establishment have been associated with root circling and ascending, descending, and kinked roots occurring in nursery containers. à e main goal of this study was to find methods of producing from seed Swietenia mahagoni (L.) Jacq. with straight, non-deformed roots. In contrast to smooth-sided (SM) propagation containers (liners), roots grown in pots constructed of thin paper were straight with few deflections. Root pruning 12-month-old SM liners when shifting to 3.8 L containers dramatically reduced the imprint on the root system left by root deflections. Aggressive growth at the bottom of 3.8 L and 9.5 L smooth-sided containers appeared to inhibit growth in horizontal roots closer to the substrate surface, and resulted in a vertically oriented root system. In contrast, growing trees in 3.8 L and 9.5 L containers with exceptionally porous walls produced a more horizontal-oriented root system similar to well-anchored trees in the landscape. Vertical roots were discouraged from developing due to an elevated and porous bottom, forcing roots to grow more horizontally higher in the root ball profile. Root deflections increased with retention time in all containers.

Keywords
  • Air Root Pruning
  • Deflected Roots
  • Descending Roots
  • Field-grown Trees
  • Horizontal Roots
  • Liners
  • Mechanical Root Pruning
  • Propagation
  • Straight Roots
  • Swietenia mahagoni

Trees with some large diameter, straight roots close to the soil surface are well anchored in shallow (Coutts et al. 1990) and deep soils (Gilman and Wiese 2012). ài s compels development of field and container nursery production systems that mimic this root morphology. Roots on established trees often proliferate close to the surface in soil with low oxygen content typical in disturbed urban soils (Gilman et al. 1987; Watson and Kupkowski 1991). Some roots elongate from existing short roots within the root ball, from cut roots at the top edge of the root ball, or adventitiously from the flare. Many large roots are oriented downward in the planted root ball for certain production systems and species (Hewitt and Watson 2009; Gilman and Orfanedes 2012). à e tree redirects the root system toward the surface after planting, which contributes to transplant shock as the tree generates either adventitious roots from near the trunk or new roots from root pruning cuts.

à e downward growth and circling of roots that result from deflection in propagation (liner) container encourages new roots to grow from the bottom of the liner root ball once planted into field soil or a larger container (Salonius et al. 2000). Decades ago, Harris et al. (1971) recognized that root pruning seedlings as they were shifted could reduce the imprint left by root deflections. Research on liners used in reforestation efforts also suggests that root-pruned seedlings produce a more symmetrical root system with ample surface roots (Krasowski 2003).

Roots on shade trees in larger containers also deflect around and downward, often proliferating at the bottom (Marshall and Gilman 1998), likely due to availability of suitable air, nutrition, and water at the bottom. Root defects of temperate (Weicherding et al. 2007) and tropical (Gilman and Orfanedes 2012) trees growing in containers with more or less smooth sides are fairly easy to remove with mechanical root pruning (shaving all roots and substrate from the periphery), because many roots are at the extreme edge of the root ball. From field observations, evaluation of these practices is only now beginning in mainstream horticulture operations.

Certain container types have been associated with reduced root defects at the root ball periphery (Arnold and McDonald 2006; Gilman et al. 2010). Treating the interior plastic container surface with copper is a time-tested, effective method for reducing root growth on the periphery of container root balls (Burdett 1978; Struve 1993; Marshall and Gilman 1998). Orlander (1982) and Ortega et al. (2006) found that exposing the open container bottom to air (air pruning) resulted in fewer deflected roots in the propagation container. à e number and total length of Acer rubrum L. roots from stem cuttings deflected up, around, and down by container walls were approximately an order of magnitude greater in four types of plastic containers compared to those made from thin paper (Gilman et al. 2012). ài s was presumably due to a combination of root tip dieback on roots growing through the paper and into the air outside the container (i.e., air pruning), and growth of some of these roots into adjacent containers.

à e objective of this study was to find a nursery production system that produced a root ball with attributes similar to those of well-anchored landscape trees; i.e., with straight roots, some close to the surface. Mahogany [Swietenia mahagoni (L.) Jacq.] was chosen due to: 1) its popularity as an urban landscape tree in tropical and subtropical regions of Florida, U.S., and in the Caribbean, and 2) a general lack of nursery production research on tropical shade tree root systems.

MATERIALS AND METHODS

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On February 11, 2009, in Loxahatchee, Florida (USDA hardiness zone 10a), mahogany seeds were placed into propagation (liner) containers in substrate consisting of 45% super fine pine bark, 20% Florida peat, 10% horticultural perlite, 15% Allgro compost, and 10% coarse sand. àr ee propagation container types tested were: 1) Bottomless Ellepot (EP) constructed of paper 50 mm diameter × 90 mm tall, with a volume of 137 cm3 (Ellegaard, Esbjerg, Denmark, Ellepot paper made by Ahlstrom Stalldalen AB, Stalldalen Sweden from spruce, pine, and polyester long fibers, 27g/m2, 190 microns thick, 1320 N/m dry tensile strength in machine direction, 2.0 N tear strength), arranged 10 mm apart in a plastic tray (27 cm × 53 cm), which exposed 100% of the paper sides to air and rested on a plastic ring (8 mm wide) as part of the holder tray; 2) EP with same dimensions placed in a tray of smooth (EPS) black plastic cells (60 mm tall × 50 mm wide), spaced about 5 mm apart; and 3) a tray of smooth-sided (SM) black plastic containers 40 mm top diameter × 90 mm tall (volume 105 cm3) with a slightly tapered cone and a single drainage hole at the bottom. Trays (each with 40 to 55 containers) were arranged in a randomized fashion on wire mesh benches 80 cm from the ground in full sun in a non-climate controlled, open-sided greenhouse.

Retained in Propagation Container (5 months)

On July 27, 2009 (5 months retention time in propagation container), trees were either 1) washed of substrate for root evaluation, 2) shifted into 3.8 L containers, or 3) retained in the propagation containers. On 10 randomly chosen, washed trees, roots >1 mm diameter were evaluated for number of roots in the top half of root ball that branched, estimated % of total root ball root length that was in the top half of the root ball, tap root deflected by liner bottom or not, tap root length after deflection, number of primary lateral roots deflected by the container bottom, number of primary lateral roots deflected downward by the container sides, and a visual estimate of where active root growth was occurring: either mostly in the top half of root ball, mostly in the bottom half of root ball, or evenly distributed in the root ball. Tree height and trunk diameter at substrate level were also recorded.

One-hundred liners of each propagation container type were shifted into either 3.8 L, 1) black plastic smooth-sided slightly-tapered containers (SCI; 15.5 cm top diameter × 15.5 cm tall; Nursery Supplies, Inc., Chambersburg, Pennsylvania, U.S.) or 2) into containers with exceptionally porous walls and bottom (Pioneer pot; PC1; 19 cm top diameter × 17 cm tall, all container surfaces composed of about 15% plastic and 85%, air including a bottom elevated 8 cm from ground, Pioneer Farms, Visalia, California, U.S.) and placed several cm apart on woven ground cloth, on the ground, pot-to-pot in a randomized fashion. Side of PC1s were lined with paper (as described in EP) to ensure substrate would not leach through the large (10 mm square) openings in the side. à e resulting experimental design was a complete factorial with three propagation container types × two 3.8 L container types, totaling 600 trees. Substrate volume was equivalent in both 3.8 L containers; it reached the top in the PC1 containers and was 1 cm below the top in the SM1 containers. à e EP paper was not removed when shifting into 3.8 L containers. Controlled release fertilizer (18N-6P2O5-12 K2O, Nurserymen's Sure Gro, Vero Beach, Florida, U.S.) was surface applied to substrate (60% pine bark: 30% Florida peat: 10% sand) following shifting to the 3.8 L container, and no other fertilizer was applied. Trees in 3.8 L containers were overhead irrigated typically two or three times daily in the growing season, less in the dormant season. Roots remained inside containers without rooting into the ground and without rooting into adjacent containers. Shoots were pruned once to maintain a dominant leader.

In January 2010 (6 months retention time in 3.8 L containers), trees were either 1) washed, 2) retained in 3.8 L containers, or 3) shifted to 9.5 L containers. Ten trees in both 3.8 L container types from three propagation container types (60 trees total) were washed of substrate to measure root and shoot attributes. Root (>1 mm diameter) attributes measured in 3.8 L containers included % trunk circumference circled with roots; root cull, according to Florida Grades and Standards for Nursery Stock (Anonymous 1998); number of roots deflected by propagation container; visual rating of the imprint formed by the deflected roots at the position of the liner; root depth and diameter of the 10 largest-diameter roots measured just beyond the edge of the propagation container position; number of the largest 10 roots that grew outward at less than 45 degrees to substrate surface without deflecting laterally more than 60 degrees and reached the 3.8 L container edge (straight roots); root depth and diameter at the periphery of the 3.8 L container; and diameter of the five largest horizontal (0 to 45 degrees from substrate surface) and vertical (45 to 90 degrees) roots measured just beyond the edge of the propagation container. Half of the remaining trees were retained in the 3.8 L container until September 2010 (13 months retention time in 3.8 L containers), when either the same measurements were made on eight randomly chosen trees of each treatment combination, or trees were shifted into 9.5 L containers of the same type (SC3, model PF1200,27 cm top diameter × 24 cm deep; PC3, 28 cm top diameter × 17 cm deep). Substrate volume was equivalent in both containers; it reached the top in the PC3 containers and was 1 cm below the top in the SM3 containers. The other half of the remaining 3.8 L trees was shifted January 2010 into 9.5 L containers of the same type (PC3 and SC3). Paper was not used to line the PC3 because it did not appear to be needed to retain substrate. All trees remained in 9.5 L containers for six months regardless of when they were shifted, at which time they were washed of substrate to measure roots as described for 3.8 L containers. Trees grown under the EPS treatment were not shifted into 9.5 L containers due to lack of available plants.

Retained in Propagation Container (12 months)

In February 2010, 40 trees retained in EP and 40 retained in SM propagation containers for 12 months were root pruned; 20 of each went into SC1 and 20 into PC1 3.8 L containers for a total of 80 trees (two propagation types pruned × two 3.8 L types × 20 reps). à e outer 5 mm of the root ball sides and bottom was removed with sharp scissors (Fiskars, FSK01004342) by one person to standardize procedure. à e remaining 80 trees were not root pruned when shifted into the SC1 (40 trees) and PC1 (40 trees) containers. à e completely randomized experimental design was a complete factorial with two propagation types × two 3.8 L types × two root pruning treatments × 20 reps = 160 trees. Substrate in the propagation container was positioned a few mm below the surface of the 3.8 L container substrate to account for some substrate settling around the liner root ball. Trees were placed in a randomized manner in full sun and overhead irrigated on nursery ground cloth. In August 2010 (6 months retention time in 3.8 L containers) and March 2011 (12 months retention time in 3.8 L containers), trees were shifted into 9.5 L containers of the same type. Trees remained in 9.5 L containers for six months regardless of when they were shifted, at which time root systems were washed of substrate. Measurements included those described for 3.8 L containers.

Statistical Analysis

All designs were completely randomized complete factorials. Attributes in three propagation containers harvested in July 2009 were analyzed with one-way analysis of variance (ANOVA) using the GEM procedure of SAS (version 9.2, SAS Institute, Cary, North Carolina, U.S.) (Table 1). Attributes in two 3.8 L container types shifted from three propagation liner types harvested January 2010 were analyzed with two-way ANOVA (Table 2). Attributes in two 3.8 L container types, grown from three propagation liner types, and retained 5 or 12 months in propagation, liners were analyzed with three-way ANOVA (Table 3). Attributes in two 3.8 L container types, grown from three propagation liner types, and root pruned or not, were analyzed with three-way ANOVA (Table 4). Attributes in two 3.8 L containers types retained in two propagation liner types 5 months, and harvested 6 and 13 months later, were analyzed with three-way ANOVA (Table 5). Attributes in two 3.8 L and 9.5 L container types, grown from three propagation liner types, in each of these three treatment combinations: 1) 5 months or 2) 12 months retention in propagation container without root pruning when shifting to 3.8 L container, or 3) 12 months retention with root pruning, were analyzed with three-way ANOVA (Tables 6 and 7). Attributes in two 3.8 L and 9.5 L container types, grown from two propagation liner types for 5 months, and retained in 3.8 L containers for 6 or 13 months, were analyzed with three-way ANOVA (Table 8). Percentages were Arcsine transformed prior to analysis. Duncan's multiple range test was used to separate main effect means; interaction means were compared with LS means at P < 0.05. Main effects are presented and were averaged across insignificant factors when interactions were insignificant.

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Table 1.

Trunk diameter, tree height, and root (>1 mm diameter) attributes of mahogany [Swietenia mahagoni (L.) Jacq.] harvested from three propagation container types 5 months (July 2009) after seed germination.

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Table 2.

Effect of propagation container type on roots (>1 mm diameter) of mahogany harvested six months (January 2010) after shifting into 3.8 L containersz.

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Table 3.

Interaction of propagation container type with retention time on mahogany roots (>1 mm diameter) harvested 6 months later from 3.8 L containers.

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Table 4.

Interaction of propagation container type with root pruning on mahogany roots (>1 mm diameter) harvested from 3.8 L containers 13 months after shifting (March 2011).

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Table 5.

Interaction of 3.8 L container type with retention time on mahogany roots (>1 mm diameter) harvested from 3.8 L containers.

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Table 6.

Effect of container type on mahogany trunk diameter, tree height, and roots (>3 mm diameter) harvested in 9.5 L containers in April and October 2011.

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Table 7.

Interaction of propagation container type with 3.8 L and 9.5 L container type on mahogany roots (>3 mm diameter) harvested in 9.5 L containers April and October 2011.

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Table 8.

Effect of retention time in 3.8 L container on mahogany in 9.5 L containers September 2010 and April 2011.

RESULTS

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Three-way interactions were mostly insignificant, so they are not described in this analysis. Mahogany propagated in SM had slightly smaller trunk diameter and were shorter than trees in EP when harvested from the propagation container (Table 1). Trees in EP had greater root branching and root length in the top half of liner root balls, fewer deflected tap roots and lateral roots, and actively growing roots more evenly distributed vertically when compared to SM and EPS (Table 1; Figure 1).

Figure 1.
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Figure 1.

Root systems after 5 months in three propagation containers. The large-diameter lateral woody roots emerging from the tap root in EP are lacking on the other two.

Mahogany harvested from both 3.8 L container types that were propagated in EPS had a much larger percentage of the trunk circled at the liner position (78%), produced more trees graded as root culls (79%), and the imprint on the root system imposed by the propagation container was highly visible (rating = 4.6) when compared to seedlings grown in SM and EP (Table 2). Trees propagated in EP had the least deflected (lower % trunk circled, % culls, imprint rating) root systems, and those from SM had shallower roots than EPS.

Mean root depth was greater in both 3.8 L container types measured just beyond the position of the liner root ball when trees were retained in propagation containers 12 months (87 mm) compared to 5 months (50 mm, data not shown). Response to retention time depended on the propagation container type for four measured root attributes (Table 3). In contrast to SM propagation containers, increasing retention time in EP containers had no impact on % trunk circled, % root culls, and number of straight roots in 3.8 L containers. When held five months, propagation container type had no impact on number of roots deflected at the position of the container; however, when held 12 months, fewer roots deflected in EP than in SM containers.

Root pruning SM liners by shaving (pruning) 5 mm from the periphery reduced by a factor of 4 or 5 the % trees in both 3.8 L containers graded as culls and % trunk circled, respectively (Table 4). Root pruning EP liners had no impact on 3.8 L trees (Table 4) because there were few roots deflected by the EP periphery (Table 1). Root pruning SM also increased the % of total root (>3 mm diameter) number (56%, root pruned; 42%, not root pruned; P < 0.05) that grew to the periphery of both 9.5 L containers (data not shown).

Percentage of total-tree root cross-sectional area (CSA) in the top 2 cm measured at the periphery of the 3.8 L root ball was larger for trees grown in PC1 than in SC1 containers for both retention times from both propagation containers (Table 5). Both the number of horizontal roots (those growing 0 to 45 degrees from the surface) and CSA of the five largest horizontal roots were approximately two to three times larger for trees in PC1 than SM1 containers. à e ratio of diameter in the five largest horizontal to diameter in the five largest descending roots (those growing 45 to 90 degrees from surface) was eight and three times greater for PC1 than SC1 for 6 and 13 months retention time, respectively. Growing trees in SC1 containers resulted in a greater arc without roots (>1 mm diameter) than growing in PC1 after 6 months in 3.8 L containers; there was no difference at 13 months. Root depth for trees from both propagation container types was not affected by 3.8 L container type 6 months after shifting but was significantly greater in SC1 than PC1 13 months after shifting (Table 5).

Impact from growing mahogany trees in 3.8 L and 9.5 L containers of two types was consistent (i.e., there was no interaction) across propagation container type, retention time in propagation container, and root pruning for 11 measured attributes (Table 6; Figure 2). Trees harvested from SC3 containers had slightly larger trunk diameter and total-tree height (P < 0.05) than trees from PC3. Roots on trees from SC3 had higher values of attributes associated with lower quality, including % trunk circled with roots, 3.8 L container imprint rating, root cull (graded according to Florida Grades and Standards, Anonymous 1998), and total deflected root length. Trees in PC3 containers had about six times the number of straight roots (69% vs. 11% of roots > 3 mm diameter) as those in SC3 containers. Trees in PC3 had 44% of root system CSA deeper than 8 cm at the periphery of the 9.5 L container, whereas 83% was positioned there on trees in SC3 containers. Ratio CSA of five largest horizontal to five largest descending roots was 49 times greater on trees from PC3 than SC3 containers (Table 6; Figure 2).

Figure 2.
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Figure 2.

Root systems in 9.5 L containers for six months, grown in four combinations of propagation container and larger (3.8 L and 9.5 L) container.

Impact on growing trees in 3.8 L and 9.5 L containers depended on the propagation container type for four root attributes (Table 7). Growing trees in EP and then shifting to PC1 and PC3 resulted in the least % trunk circled and % trees with roots that touched or crossed within the dimensions of the propagation container. For both propagation container types, growing trees in PC3 resulted in a threefold or more increase in number of horizontal straight roots (those > 3 mm diameter) and % roots that grew to the 9.5 L container periphery compared to trees in SC3. à e longer retention time in both 3.8 L containers was associated with greater root circling and deflection, reduced quality, and slightly greater depth of horizontally oriented roots (Table 8).

DISCUSSION

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Retaining trees in containers for different time periods, and root pruning or not when shifting the liner, resulted in few meaningful differences in trunk diameter and tree height at the end of the study when trees were in 9.5 L containers; container type had only a slight effect. Trees in SC containers were larger than those in PC probably due to drier conditions (not measured) in PC containers. ài s was attributable to the porous nature of the container sides and bottom; fabric containers with porous sides have been shown to increase evaporation from the container root ball (Arnold and McDonald 2006). Irrigation management could be adjusted to maintain higher moisture content.

Finished liners in EP had attributes associated with high quality root systems best described as an abundance of horizontal straight roots growing from an aborted tap root (Balisky et al. 1995; Svensen et al. 1995); roots in the other two liners were deflected downward and around the container (Table 1; Figure 1). EP propagation containers that were inserted into smooth-sided liner cells (EPS) produced root systems similar to those in SM (Table 1), which indicated that the paper comprising the sides of EP should be exposed to air, not placed against a solid plastic wall. When finished in 3.8 L containers, root systems from EPS containers had a more prominent liner imprint (Harris et al. 1971) than those propagated in SM (Table 2). à e slim air gap between the plastic sides and the EP paper created an ideal environment for root growth and caused this imprint formed by roots circling, ascending, and descending mostly outside of the paper. Mahogany should not be grown using the EPS system because it encouraged a severe root imprint at the position of the liner. In contrast, trees propagated in EP and finished in either 3.8 L container type had almost no measurable root circling or imprint at the position of the liner (Table 2).

Mahogany root defects at the liner position on trees in 3.8 L containers increased with retention time in SM propagation containers but not for EP containers (Table 3) as in other studies (Salonius et al. 2000; Gilman et al. 2012). However, root pruning SM liners retained 12 months when shifting to 3.8. L containers dramatically reduced defects at the liner position (Table 4) without impacting trunk or height growth (data not shown). ài s enhancement of quality did not occur for trees propagated in EP because there were far fewer defects to remove (Table 1). Mechanical root pruning was also a reliable method of managing roots of other tree species when shifting liners to larger containers (Gilman et al. 2012), or when planting into field soil (Krasowski and Owens 2000). ài s eliminates the imprint imposed on the root system by the container, which reduces the likelihood of stem girdling roots and can enhance anchor-age (Gilman and Wiese 2012).

Propagation container type failed to influence consistently any measured attribute across both 9.5 L container types; i.e., the effect of propagation type depended on which larger container was used when data was averaged across 5 and 12 months retention time in propagation containers and root pruning (Table 7). In contrast, the effect of larger container type (either PC or SC) was consistent for nine root attributes of trees propagated from either propagation type (Table 6). ài s analysis could falsely lead us to conclude that root quality depended more on the 3.8 L and 9.5 L container type, and less on the propagation container type. However, when data was averaged across retention time in 3.8 L containers on trees retained for 5 months in propagation containers, propagation type had a significant effect on root morphology in the 9.5 L root balls. For example, root defects at the SM liner position including % trunk circled (51), % culls (42), and imprint rating (3.7) were much greater (P < 0.01) than the same attributes for trees grown in EP propagation containers (8%, 3%, and 1.7, respectively, data not shown). ài s analysis shows that both propagation container and the larger container impacted root quality.

à e deeper and deflected nature of the root system in finished SM liners (Table 1) likely 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 the propagation liner in either larger container type. à e lack of root deflection in EP propagation containers (Table 1) was responsible for the small imprint at that position and far greater number of roots reaching the side walls (periphery) of the PC 9.5 L container (Table 7; Figure 2). Root tips in EP liners remained in the horizontal position near the liner periphery without deflection, which positioned them for growing horizontally into the PC container. However, in SC 9.5 L containers, root defects on trees propagated in EP mimicked those of trees propagated in SM liners, suggesting that the benefits of growing a high-quality root system in the liner (i.e., in EP) disappeared when shifting into a larger SC container. ài s was attributable to the largest roots from both propagation container types growing downward from the bottom of the liner to the bottom 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) as others have found for smaller containers (Selby and Seaby 1982). Aggressive 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 finished 9.5 L SC trees (Figure 2). Deflection of structural roots downward in the container forced them to grow parallel and cross one another directly under the trunk (Table 7) causing constrictions and inclusions that can restrict passage 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). ài 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 elevated bottom which effectively root pruned them. Air pruning at the bottom appeared similar to that of at least one other container that prunes with air (Gilman et al. 2010). Inhibition of descending vertical roots induced formation of new roots or growth on existing roots close to the soil surface, and promoted growth in horizontal-oriented roots distributed throughout the root ball profile. à e tremendous (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). Neither of these phenomena occurred in SC containers. Mahogany trees with horizontal-oriented 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 better anchorage (Gilman and Harchick 2014).

CONCLUSION

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Mahogany root systems in a container can be grown with attributes associated with well-anchored landscape trees (i.e., with straight roots, some close to the surface).

Acknowledgments

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à 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.

  • © 2014, International Society of Arboriculture. All rights reserved.

LITERATURE CITED

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  1. ↵
    1. Anonymous
    . 1998. Florida Grades and Standards for Nursery Plants. Florida Department of Agriculture and Consumer Services, Gainesville, Florida, U.S.
  2. ↵
    1. Arnold, M.A., and
    2. G.V. McDonald
    . 2006. Shrub rose responses to production in Smart Pots and conventional containers using two contrasting substrates. Subtropical Plant Science Journal of the Rio Grande Valley Horticulture Society 58:1–4.
    OpenUrl
  3. ↵
    1. Balisky, A.C.,
    2. P. Salonius,
    3. C. Walli, and
    4. D. Brinkman
    . 1995. Seedling roots and forest floor: Misplaced and neglected aspects of British Columbia’s reforestation effort. Forestry Chronicle 71:59–65.
    OpenUrl
  4. ↵
    1. Burdett, A.N.
    1978. Control of root morphogenesis for improved stability in container-grown lodgepole pine. Canadian Journal of Forest Research 8:483–486.
    OpenUrl
  5. ↵
    1. Coutts, M.P.,
    2. C. Walker, and
    3. A.C. Burnand
    . 1990. Effects of establishment method on root form of lodgepole pine and Sitka spruce and on the production of adventitious roots. Forestry 63:143–159.
    OpenUrlCrossRef
  6. ↵
    1. Gilman, E.F., and
    2. C. Harchick
    . 2014. Container design influences Swietenia mahagoni root attributes and anchorage after landscape planting. Arboriculture & Urban Forestry 40:27–35.
    OpenUrl
  7. ↵
    1. Gilman, E.F., and
    2. C. Wiese
    . 2012. Root pruning at planting and planting depth in the nursery impact root system morphology and anchorage. Arboriculture & Urban Forestry 38:232–239.
    OpenUrl
    1. Gilman, E.F., and
    2. M. Orfanedes
    . 2012. Root pruning and planting depth impact root morphology in containers. Journal of Environmental Horticulture 30:173–181.
    OpenUrl
  8. ↵
    1. Gilman, E.F.,
    2. I.A. Leone, and
    3. F.B. Flower
    . 1987. Effect of soil compaction and oxygen content on vertical and horizontal root distribution. Journal of Environmental Horticulture 5:33–36.
    OpenUrl
  9. ↵
    1. Gilman, E.F.,
    2. M. Paz, and
    3. C. Harchick
    . 2010. Effect of container type on root form and growth of red maple. Journal of Environmental Horticulture 28:1–7.
    OpenUrl
    1. Gilman, E.F.,
    2. M. Paz.,
    3. D. Meador, and
    4. P. Fisher
    . 2012. Propagation container type, time in container, and root pruning affect root development of young Acer rubrum. Journal of Environmental Horticulture 30:150–160.
    OpenUrl
  10. ↵
    1. Harris, R.W.,
    2. W.B. Davis, N.W. Stice, and
    3. D. Long
    . 1971. Influence of transplanting time in nursery production. Journal American Society Horticulture Science 96:109–110.
    OpenUrl
  11. ↵
    1. Hewitt, A., and
    2. G. Watson
    . 2009. Bare root liner production can alter tree root architecture. Arboriculture & Urban Forestry 27:99–104.
    OpenUrl
  12. ↵
    1. Krasowski, M.J.
    2003. Root system modifications by nursery culture reflect on post-planting growth and development of coniferous seedlings. Forest Chronicle 79:882–891.
    OpenUrl
  13. ↵
    1. Krasowski, M.J., and
    2. J.N. Owens
    . 2000. Morphological and physical attributes of root systems and seedlings growth in three different Picea glauca reforestation stock. Canadian Journal of Forest Research 30:1669–1681.
    OpenUrl
  14. ↵
    1. Lindström, A., and
    2. G. Rune
    . 1999. Root deformation in plantations of container-grown Scots pine trees: Effects on root growth, tree stability and stem straightness. Plant and Soil 217:29–37.
    OpenUrlCrossRef
  15. ↵
    1. Marshall, M.D., and
    2. E.F. Gilman
    . 1998. Effects of nursery container type on root growth and landscape establishment of Acer rubrum L. Journal of Environmental Horticulture 16:55–59.
    OpenUrl
  16. ↵
    1. H. Hulten
    1. Orlander, G.
    1982. à e air-pruned seedling - A solution to the root-deformation problem? pp. 91–94. In: H. Hulten, (Ed.). Root deformation of forest tree seedlings - proceedings of a Nordic symposium, Garpenberg, 1981. Swedish University at Agricultural Sciences, Department of Forest Yield Research. Report No. 11.
  17. ↵
    1. Ortega, U.,
    2. J. Majada,
    3. A. Mena-Petite,
    4. J. Sanchez-Zabala,
    5. N. Rodriguez-Itturrizar,
    6. K. Txarterina,
    7. J. Azpitarte, and
    8. M. Duñabeitia
    . 2006. Field performance of Pinus radiata D. Don produced in nursery with different types of containers. New Forests 31:97–112.
    OpenUrl
  18. ↵
    1. Salonius, R,
    2. K. Beaton, and
    3. B. Roze
    . 2000. Effects of cell size and spacing on root density and field performance of container-reared black spruce. Information Report M-X-208E, Canadian Forest Service, Atlantic Forestry Centre, Frederickton, New Brunswick, Canada.
  19. ↵
    1. Selby, C., and
    2. D.A. Seaby
    . 1982. The effect of auxins on Pinus contorta seedling root development. Forestry 55:125–135.
    OpenUrlCrossRef
  20. ↵
    1. Struve, D.K.
    1993. Effect of copper-treated containers on transplant survival and regrowth of four tree species. Journal of Environmental Horticulture 11:196–199.
    OpenUrl
  21. ↵
    1. Svensen, S.E.,
    2. D.L. Johnston, and
    3. B.L. Coy
    . 1995. Shoot and root responses of eight subtropical species grown in cupric hydroxide-treated containers. HortScience 30:249–251.
    OpenUrlAbstract/FREE Full Text
  22. ↵
    1. Watson, G.W., and
    2. G. Kupkowski
    . 1991. Effects of a deep layer of mulch on the soil environment and tree root growth. Journal of Arboriculture 17:242–245.
    OpenUrl
  23. ↵
    1. Weicherding, P.J.,
    2. C.P. Giblin, J.H. Gillman, D.L. Hanson, and
    3. G. Johnson
    . 2007. Mechanical root-disruption practices and their effect on circling roots of pot-bound Tilia cordata Mill, and Salix alba L. ‘Niobe’. Arboriculture & Urban Forestry 33:43–47.
    OpenUrl
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Arboriculture & Urban Forestry (AUF): 40 (1)
Arboriculture & Urban Forestry (AUF)
Vol. 40, Issue 1
January 2014
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Container Production Strategies Influence Root Ball Morphology
Edward F. Gilman, Maria Paz
Arboriculture & Urban Forestry (AUF) Jan 2014, 40 (1) 16-26; DOI: 10.48044/jauf.2014.002

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Container Production Strategies Influence Root Ball Morphology
Edward F. Gilman, Maria Paz
Arboriculture & Urban Forestry (AUF) Jan 2014, 40 (1) 16-26; DOI: 10.48044/jauf.2014.002
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