Established forest trees planted from small containers are less stable at the point where roots f... more Established forest trees planted from small containers are less stable at the point where roots fork, bend or branch as a result of deflection by container wall, but less is known about the post-transplant impact of root deflections resulting from growing trees in large containers. We either root pruned by shaving off the periphery of the #3 container root ball as it was planted into the #15 container or did not root prune on 5 tropical and 2 temperate tree species. Shaving did not affect trunk caliper or tree height on the seven species tested under the conditions of this study. Shaving removed the entire outer and bottom 2.5 cm (1 in) of the root ball and reduced or eliminated culls on five of seven species. The largest diameter roots on trees in #15 containers that were not root pruned when shifted from #3 containers were kinked, descended down the container wall, or circled at the position of the #3 container. These root defects were largely missing on trees with root balls that...
Leyland cypress, laurel oak and slash pine were grown for 18 months in plastic containers, in fab... more Leyland cypress, laurel oak and slash pine were grown for 18 months in plastic containers, in fabric containers or directly in the field and then transplanted into field soil. There was no difference in growth between field-grown and fabric container-grown trees for laurel oak or slash pine, but field-grown leyland cypress were taller than fabric containergrown trees. Container-grown trees were smallest for all three species. Shoot : root dry weight ratio was smallest on container-grown trees because little of the root system is lost during transplanting compared to fabric and field-grown trees. Ten weeks after transplanting, weight of regenerated roots on fabric container-grown leyland cypress and slash pine was greater than on field-grown trees. Field-grown slash pine regenerated less root weight than trees produced by other production methods. Production method did not affect root regeneration of laurel oak.
Plants were grown in a 2 × 2 factorial combination of planting depth in nursery containers and at... more Plants were grown in a 2 × 2 factorial combination of planting depth in nursery containers and at a landscape installation to study effects on root architecture, growth, and mechanical stability of Magnolia grandiflora L. Planting depth into containers or landscape soil had no impact on bending stress to tilt trunks 40 months after landscape planting, and impacted neither trunk diameter nor tree height growth 68 months later. Trees planted 128 mm deep into 170 L containers had more circling roots at landscape planting and 68 months later than trees planted shallow in containers. Root pruning at landscape planting reduced the container imprint rating on the root system to one-third of that absent root pruning with only a 4 mm reduction in trunk diameter growth over 68 months. Improvement in root architecture from root pruning likely outweighs the rarely encountered downside of slightly less anchorage in an extreme weather event simulated by winching trunks. Trees planted 5 cm above g...
This study was designed to evaluate the impact of several planting depths and mulch depth, partic... more This study was designed to evaluate the impact of several planting depths and mulch depth, particle size, and placement on tree establishment. Except for one period 2 weeks after transplanting, mulch depth and mulch particle size did not affect first-year stress (stem xylem potential) or growth of 76 mm (3 in.) caliper, balled-and-burlapped, transplanted live oak (Quercus virginiana Mill.). Negative effects of deep [15 mm (6 in.)] mulch 2 weeks after transplanting occurred for the mixed particlesized material only. Mulch placed over the root ball intercepted water, causing a drier root ball and resulting in greater tree stress and reduced survival following light applications of water than for trees with no mulch over the root ball. This result did not occur following heavy applications of water. Keeping the ground near trees free of vegetation chemically had the same effect on post-planting stress and growth as mulching did. Soil over the root ball resulting from deep planting int...
One codominant stem on each of 48 similar Quercus virginiana Highrise® trees was pruned to evalua... more One codominant stem on each of 48 similar Quercus virginiana Highrise® trees was pruned to evaluate impact of pruning severity on growth suppression and partitioning. Targeted pruning severity (0, 25, 50 or 75% foliage and subtending branches removed) based on visual estimates of two people correlated well (r2 = 0.87) with the ratio stem cross-sectional area removed: crosssectional area at base of the pruned codominant stem. Pruning reduced cross-sectional area growth on codominant stems compared to the leader stem that was not pruned, especially during the first 12 months following pruning. Increased pruning severity reduced cross-sectional area growth on the pruned stem in proportion to amount of foliage removed. In each of three years following pruning, cross-sectional area of the unpruned leader stem increased more on trees receiving targeted pruning severities of 25% or 50% than trees pruned with the 75% severity or trees not pruned. Shift in growth from the pruned to unpruned ...
Branch diameter relative to the trunk diameter (aspect ratio) affected the extent of discolored a... more Branch diameter relative to the trunk diameter (aspect ratio) affected the extent of discolored and decayed wood in the trunk of seedling-propagated red maple (Acer rubrum L.) after branch removal. More discoloration resulted from removing codominant stems than removing branches that were small compared to the trunk. Removing limbs that originated from lateral buds resulted in the same amount of discoloration and decay as removing suppressed limbs that were once the leader. This result provides indirect evidence that a small codominant stem suppressed by pruning techniques designed to slow its growth rate can result in a branch protection zone at the union. There was no relation between the presence of a bark inclusion and decay 4 years after making pruning cuts.
The effect of branch morphological characteristics on hydraulic segmentation in red maple branch ... more The effect of branch morphological characteristics on hydraulic segmentation in red maple branch junctions was determined using hydraulic conductivity measurements. Relative branch size impacted hydraulic conductivity at the branch junction. Conductivity ratios were directly proportional to the ratio of branch diameter to stem diameter. Junctions with perpendicular branches showed lower hydraulic conductivities than more upright branches. The presence of visible branch collars was a good indicator of low branch junction conductivity. Branches having pith that was continuous with trunk pith were associated with codominant stems that had high branch junction conductivity. Branch junction hydraulic conductivity was positively correlated with the amount of discolored wood development after branch removal. This finding may indicate that similar anatomical properties are responsible for both branch junction decay resistance and hydraulic segmentation.
After 40 months in air root pruning containers, Quercus virginiana ‘SDLN’ Cathedral Oak® live oak... more After 40 months in air root pruning containers, Quercus virginiana ‘SDLN’ Cathedral Oak® live oak planted 3.8 and 8.9 cm (1.5 and 3.5 in) deep from rooted cuttings had greater caliper than trees planted at 1.3 cm (0.5 in) below substrate surface. Trees in the 1.3 cm (0.5 in) deep treatment grew taller than all other trees except for those in the 3.8 cm (1.5 in) deep treatment. Most (80%) trees were graded as culls according to root evaluations in the Florida Grades and Standards for Nursery Stock. This resulted mostly from roots circling and crossing the top of the root ball in the #3 and/or #15 container sizes. Trees planted 6.4 cm (2.5 in) deep in #3s, then 6.4 cm deep in #15s, and 6.4 cm deep in #45s [19 cm (7.5 in) total depth] had fewer, smaller diameter, and deeper primary roots than trees planted at all other depths. The presence of a trunk flare and surface roots decreased with increasing planting depth indicating that these could be used as an indicator of primary root dept...
This study was designed to measure evaporation from substrate-filled and soil-filled containers (... more This study was designed to measure evaporation from substrate-filled and soil-filled containers (360 L) to simulate a planted root ball. There was no difference in evaporation between mulched and non-mulched soil-filled lysimeters in any consecutive three-day period following irrigation. In contrast, more evaporation occurred the first dry day after irrigation from substrate-filled lysimeters covered with mulch than from those without mulch. Non-mulched substrate-filled lysimeters lost more water to evaporation than mulched lysimeters in the second day after irrigation. Cumulative evaporation through day two was identical for mulched and non-mulched substrate treatments. Cumulative evaporation through the third dry day, after irrigation, was 0.5 L greater from non-mulched lysimeters because of higher evaporation. Mulched or not, only about one liter evaporated daily from the surface of the substrate-filled or soil-filled lysimeters during consecutive, three-day rain-free periods fol...
Quercus virginiana Mill. Highrise® were planted into 10 L and then 57 L plastic nursery container... more Quercus virginiana Mill. Highrise® were planted into 10 L and then 57 L plastic nursery containers at two depths for a total of four depth combinations, and then root pruned in one of three different manners when planted into the landscape. Nursery planting depth had no impact on growth in the nursery or bending moment required to tilt trunks in the first two years following landscape planting. Root pruning when planting into landscape by either method tested had no effect on growth the first two years. Number of roots circling inside the root ball was reduced by shaving or deep root ball slicing two growing seasons after planting. Root balls that were either sliced or shaved generated more roots in landscape soil one growing season after landscape planting than those that were not root pruned, which probably explained the greater bending moment required to pull trees out of the ground. Total cross-sectional root area one growing season after landscape planting was greater on shaved...
Some trees uproot in storms apparently due to root deflections that occur during nursery producti... more Some trees uproot in storms apparently due to root deflections that occur during nursery production. Root deflection in a nursery container may lead to poor anchorage because of insufficient root growth into the landscape soil, and container volume/tree size at planting may influence root deflection. This study was designed to evaluate establishment, root growth, and anchorage six years after planting Acer rubrum L. trees of four different sizes from four corresponding container volumes and maintaining them with two irrigation regimes. Impact of mulch on establishment and root growth was also evaluated. Trees from the largest containers grew slowest in the first three years due primarily to water stress. Trunk tilt during winching tests increased due to greater root deflection, less mass of the root-soil plate, and reduced root growth into the landscape soil with increasing container volume and tree size. In contrast to the poorly anchored larger trees that had most of their large r...
Fertilizer recommendations for producing shade trees in nursery field soil in North America appea... more Fertilizer recommendations for producing shade trees in nursery field soil in North America appear to be based on tradition and tree performance; there is little empirical data. This study was designed to examine efficacy of reducing traditional or historical fertilizer amount (rate) and number of applications for two taxa and to present a protocol for growers to test fertilizer use efficiency. A traditional rate of fertilizer was applied along with four others: zero, one-third, two-thirds, or one-and-one-third traditional. Fertilizer was divided into one, two, three (traditional), or four equal amounts applied during the growing season. The study was conducted on a fine sand field soil with 680 trees of each taxa in adjacent plots of the same field. There were 16 factorial treatment combinations plus a non-fertilized control. Fertilizer rate cut to one-third of the historical rate, and number of applications reduced from three to either one or two, resulted in little if any reducti...
Propagation containers modify root systems, which affect post-planting anchorage in reforestation... more Propagation containers modify root systems, which affect post-planting anchorage in reforestation efforts, but little is known about larger-sized trees typical in urban landscapes. The main goal of this study was to determine the role of root morphology on postplanting anchorage and growth on Swietenia mahagoni (L.) Jacq., a common landscape tree in warm climates. Two propagation container types, two larger container types, and root pruning were used to impose various root morphologies inside root balls. Anchorage was evaluated by winching trees at two bending stresses to simulate wind events. Interaction between propagation container type and root pruning when the liner was shifted into 3.8 L containers prevented either from consistently influencing anchorage. Trunk tilt (i.e., instability) immediately following pulling was greatest for trees with the most root CSA deflected by the 9.5 L container; trees with straighter main roots in the root ball were better anchored. Researchers ...
Trees of live oak (Quercus virginiana Mill.) were container-grown (CG) or field-grown (FG) to a m... more Trees of live oak (Quercus virginiana Mill.) were container-grown (CG) or field-grown (FG) to a mean trunk diameter of 9.4 cm (3.7 in), transplanted into sandy soil, and established with frequent or periodic irrigation. Three years after transplanting, trees were harvested with a 1.5 m (60 in) diameter tree spade. Root number and root cross-sectional area was evaluated for all roots at the periphery of the tree-spade-dug root ball. Despite similar increases in trunk diameter, FG trees had greater root number and root cross-sectional area than CG trees. The greater root cross-sectional area occurred in roots 5–20 mm (0.2–0.8 in) in diameter at soil depths of 0–25 cm (0–9.8 in) and 75–100 cm (29.5–39.3 in). Irrigation frequency after transplanting had no effect on root number in FG trees. However, root number in CG trees was lower without frequent irrigation.
Irrigation placement and irrigation volume during field production of live oak (Quercus virginian... more Irrigation placement and irrigation volume during field production of live oak (Quercus virginiana Mill.) in a sandy soil had no effect on trunk caliper [mean = 6.3 cm (2.5 in)] or tree height [mean = 3.8 m (12.4 ft)]. Root pruning had no impact on caliper and a slight (P < 0.06) impact on height. Irrigation placement and volume had little effect on number of cut roots at the edge of the root ball. Root pruning with a hand spade or in combination with root-pruning fabric placed under the liner at planting increased the number of roots at the edge of the root ball. Root pruning with fabric in combination with spade pruning increased the small-diameter (<5 mm) root weight: shoot ratio but reduced the total root weight: shoot ratio. Irrigation placement and volume during production did not affect summer nor winter digging survival. Trees that were not root pruned had poorer survival in the summer and winter digging seasons than those receiving either of the root-pruned treatments...
Irrigation frequency and volume effects were evaluated on recently installed #3 container grown s... more Irrigation frequency and volume effects were evaluated on recently installed #3 container grown shrubs of three taxa, Ilex cornuta Lindl. & Paxt. ‘Burfordii Nana’, Pittosporum tobira Thunb. ‘Variegata’, and Viburnum odorotissimum Ker Gawl. Irrigation frequency and volume had no effect on Pittosporum at any time for any measured root or shoot parameter. Irrigation frequency and volume had no effect on Ilex and Viburnum canopy biomass, root biomass, root dry weight:canopy dry weight ratio, and stem water potential at any time after planting. Canopy growth was affected by irrigation treatment only for Viburnum plants installed in May 2004, and growth response to more frequent irrigation only occurred while plants were irrigated, with no lasting impact on growth once irrigation ceased. Root spread and root spread:canopy spread ratio for only one species, Ilex, were influenced by irrigation treatment. Applying excessive irrigation volume (in this case 9L) reduced root dry weight: shoot d...
Root form is governed by seedling genetics and soil characteristics including texture, compaction... more Root form is governed by seedling genetics and soil characteristics including texture, compaction, depth to the water table, fertility, moisture content and other factors. Trees develop lateral roots growing parallel to the surface of the soil. These are generally located in the top 30 cm (12 in) of soil. Fine roots emerge from lateral roots and grow into the soil close to the surface. If soil conditions permit, some trees grow tap and other vertically oriented roots capable of penetrating several feet into the soil. Many trees, particularly those planted in urban landscapes, do not generate tap roots. Lateral roots spread to well beyond the edge of the branches. Their growth in governed by competition from other plants, available water, soil temperature, fertility, stage of shoot growth and other factors.
Cultural factors influencing root growth in the landscape or nursery include soil management, irr... more Cultural factors influencing root growth in the landscape or nursery include soil management, irrigation, fertilization, shoot pruning and root pruning. These affect root density, depth of penetration, spread, vertical distribution in the soil profile and mineral uptake. Root morphology varies widely among genera, species and individuals within a species. The distribution, length and weight of roots within the root ball of transplanted field-grown trees can be modified with cultural management practices. Growth of transplanted trees may be affected by these modifications. Root spread diameter increases at a rate of 0.9–2.4 m (36–96 in)/year following planting. From 1 to 10 years is required to replace the pre-transplant root system for trees transplanted from field nurseries. Root system in urban environments can be modified by cultural techniques which direct their growth.
Roots of four-year-old, field-grown southern magnolia (Magnolia grandiflora L.) were pruned in 19... more Roots of four-year-old, field-grown southern magnolia (Magnolia grandiflora L.) were pruned in 1987 once during dormancy, following the first shoot growth flush or after the second growth flush, prior to transplanting in January 1988. By the end of the 1987 growing season, root pruning at all stages of growth reduced leaf number, tree height, trunk caliper, and total-tree leaf area and weight compared with unpruned controls. Total root weight was less for trees pruned during dormancy or following the first growth flush. Root pruning increased the proportion of fine roots (0 to 5mm-diameter class) to coarse roots (>5 to 10-mm diameter class). Shoot:root ratios were not affected by root pruning. During the first year after transplanting, root pruned trees grew at a slightly faster rate than unpruned trees but growth rates were similar for root pruned and unpruned trees the second and third year after transplanting. Trees required, at most, 1 year per inch of trunk caliper to become...
Established forest trees planted from small containers are less stable at the point where roots f... more Established forest trees planted from small containers are less stable at the point where roots fork, bend or branch as a result of deflection by container wall, but less is known about the post-transplant impact of root deflections resulting from growing trees in large containers. We either root pruned by shaving off the periphery of the #3 container root ball as it was planted into the #15 container or did not root prune on 5 tropical and 2 temperate tree species. Shaving did not affect trunk caliper or tree height on the seven species tested under the conditions of this study. Shaving removed the entire outer and bottom 2.5 cm (1 in) of the root ball and reduced or eliminated culls on five of seven species. The largest diameter roots on trees in #15 containers that were not root pruned when shifted from #3 containers were kinked, descended down the container wall, or circled at the position of the #3 container. These root defects were largely missing on trees with root balls that...
Leyland cypress, laurel oak and slash pine were grown for 18 months in plastic containers, in fab... more Leyland cypress, laurel oak and slash pine were grown for 18 months in plastic containers, in fabric containers or directly in the field and then transplanted into field soil. There was no difference in growth between field-grown and fabric container-grown trees for laurel oak or slash pine, but field-grown leyland cypress were taller than fabric containergrown trees. Container-grown trees were smallest for all three species. Shoot : root dry weight ratio was smallest on container-grown trees because little of the root system is lost during transplanting compared to fabric and field-grown trees. Ten weeks after transplanting, weight of regenerated roots on fabric container-grown leyland cypress and slash pine was greater than on field-grown trees. Field-grown slash pine regenerated less root weight than trees produced by other production methods. Production method did not affect root regeneration of laurel oak.
Plants were grown in a 2 × 2 factorial combination of planting depth in nursery containers and at... more Plants were grown in a 2 × 2 factorial combination of planting depth in nursery containers and at a landscape installation to study effects on root architecture, growth, and mechanical stability of Magnolia grandiflora L. Planting depth into containers or landscape soil had no impact on bending stress to tilt trunks 40 months after landscape planting, and impacted neither trunk diameter nor tree height growth 68 months later. Trees planted 128 mm deep into 170 L containers had more circling roots at landscape planting and 68 months later than trees planted shallow in containers. Root pruning at landscape planting reduced the container imprint rating on the root system to one-third of that absent root pruning with only a 4 mm reduction in trunk diameter growth over 68 months. Improvement in root architecture from root pruning likely outweighs the rarely encountered downside of slightly less anchorage in an extreme weather event simulated by winching trunks. Trees planted 5 cm above g...
This study was designed to evaluate the impact of several planting depths and mulch depth, partic... more This study was designed to evaluate the impact of several planting depths and mulch depth, particle size, and placement on tree establishment. Except for one period 2 weeks after transplanting, mulch depth and mulch particle size did not affect first-year stress (stem xylem potential) or growth of 76 mm (3 in.) caliper, balled-and-burlapped, transplanted live oak (Quercus virginiana Mill.). Negative effects of deep [15 mm (6 in.)] mulch 2 weeks after transplanting occurred for the mixed particlesized material only. Mulch placed over the root ball intercepted water, causing a drier root ball and resulting in greater tree stress and reduced survival following light applications of water than for trees with no mulch over the root ball. This result did not occur following heavy applications of water. Keeping the ground near trees free of vegetation chemically had the same effect on post-planting stress and growth as mulching did. Soil over the root ball resulting from deep planting int...
One codominant stem on each of 48 similar Quercus virginiana Highrise® trees was pruned to evalua... more One codominant stem on each of 48 similar Quercus virginiana Highrise® trees was pruned to evaluate impact of pruning severity on growth suppression and partitioning. Targeted pruning severity (0, 25, 50 or 75% foliage and subtending branches removed) based on visual estimates of two people correlated well (r2 = 0.87) with the ratio stem cross-sectional area removed: crosssectional area at base of the pruned codominant stem. Pruning reduced cross-sectional area growth on codominant stems compared to the leader stem that was not pruned, especially during the first 12 months following pruning. Increased pruning severity reduced cross-sectional area growth on the pruned stem in proportion to amount of foliage removed. In each of three years following pruning, cross-sectional area of the unpruned leader stem increased more on trees receiving targeted pruning severities of 25% or 50% than trees pruned with the 75% severity or trees not pruned. Shift in growth from the pruned to unpruned ...
Branch diameter relative to the trunk diameter (aspect ratio) affected the extent of discolored a... more Branch diameter relative to the trunk diameter (aspect ratio) affected the extent of discolored and decayed wood in the trunk of seedling-propagated red maple (Acer rubrum L.) after branch removal. More discoloration resulted from removing codominant stems than removing branches that were small compared to the trunk. Removing limbs that originated from lateral buds resulted in the same amount of discoloration and decay as removing suppressed limbs that were once the leader. This result provides indirect evidence that a small codominant stem suppressed by pruning techniques designed to slow its growth rate can result in a branch protection zone at the union. There was no relation between the presence of a bark inclusion and decay 4 years after making pruning cuts.
The effect of branch morphological characteristics on hydraulic segmentation in red maple branch ... more The effect of branch morphological characteristics on hydraulic segmentation in red maple branch junctions was determined using hydraulic conductivity measurements. Relative branch size impacted hydraulic conductivity at the branch junction. Conductivity ratios were directly proportional to the ratio of branch diameter to stem diameter. Junctions with perpendicular branches showed lower hydraulic conductivities than more upright branches. The presence of visible branch collars was a good indicator of low branch junction conductivity. Branches having pith that was continuous with trunk pith were associated with codominant stems that had high branch junction conductivity. Branch junction hydraulic conductivity was positively correlated with the amount of discolored wood development after branch removal. This finding may indicate that similar anatomical properties are responsible for both branch junction decay resistance and hydraulic segmentation.
After 40 months in air root pruning containers, Quercus virginiana ‘SDLN’ Cathedral Oak® live oak... more After 40 months in air root pruning containers, Quercus virginiana ‘SDLN’ Cathedral Oak® live oak planted 3.8 and 8.9 cm (1.5 and 3.5 in) deep from rooted cuttings had greater caliper than trees planted at 1.3 cm (0.5 in) below substrate surface. Trees in the 1.3 cm (0.5 in) deep treatment grew taller than all other trees except for those in the 3.8 cm (1.5 in) deep treatment. Most (80%) trees were graded as culls according to root evaluations in the Florida Grades and Standards for Nursery Stock. This resulted mostly from roots circling and crossing the top of the root ball in the #3 and/or #15 container sizes. Trees planted 6.4 cm (2.5 in) deep in #3s, then 6.4 cm deep in #15s, and 6.4 cm deep in #45s [19 cm (7.5 in) total depth] had fewer, smaller diameter, and deeper primary roots than trees planted at all other depths. The presence of a trunk flare and surface roots decreased with increasing planting depth indicating that these could be used as an indicator of primary root dept...
This study was designed to measure evaporation from substrate-filled and soil-filled containers (... more This study was designed to measure evaporation from substrate-filled and soil-filled containers (360 L) to simulate a planted root ball. There was no difference in evaporation between mulched and non-mulched soil-filled lysimeters in any consecutive three-day period following irrigation. In contrast, more evaporation occurred the first dry day after irrigation from substrate-filled lysimeters covered with mulch than from those without mulch. Non-mulched substrate-filled lysimeters lost more water to evaporation than mulched lysimeters in the second day after irrigation. Cumulative evaporation through day two was identical for mulched and non-mulched substrate treatments. Cumulative evaporation through the third dry day, after irrigation, was 0.5 L greater from non-mulched lysimeters because of higher evaporation. Mulched or not, only about one liter evaporated daily from the surface of the substrate-filled or soil-filled lysimeters during consecutive, three-day rain-free periods fol...
Quercus virginiana Mill. Highrise® were planted into 10 L and then 57 L plastic nursery container... more Quercus virginiana Mill. Highrise® were planted into 10 L and then 57 L plastic nursery containers at two depths for a total of four depth combinations, and then root pruned in one of three different manners when planted into the landscape. Nursery planting depth had no impact on growth in the nursery or bending moment required to tilt trunks in the first two years following landscape planting. Root pruning when planting into landscape by either method tested had no effect on growth the first two years. Number of roots circling inside the root ball was reduced by shaving or deep root ball slicing two growing seasons after planting. Root balls that were either sliced or shaved generated more roots in landscape soil one growing season after landscape planting than those that were not root pruned, which probably explained the greater bending moment required to pull trees out of the ground. Total cross-sectional root area one growing season after landscape planting was greater on shaved...
Some trees uproot in storms apparently due to root deflections that occur during nursery producti... more Some trees uproot in storms apparently due to root deflections that occur during nursery production. Root deflection in a nursery container may lead to poor anchorage because of insufficient root growth into the landscape soil, and container volume/tree size at planting may influence root deflection. This study was designed to evaluate establishment, root growth, and anchorage six years after planting Acer rubrum L. trees of four different sizes from four corresponding container volumes and maintaining them with two irrigation regimes. Impact of mulch on establishment and root growth was also evaluated. Trees from the largest containers grew slowest in the first three years due primarily to water stress. Trunk tilt during winching tests increased due to greater root deflection, less mass of the root-soil plate, and reduced root growth into the landscape soil with increasing container volume and tree size. In contrast to the poorly anchored larger trees that had most of their large r...
Fertilizer recommendations for producing shade trees in nursery field soil in North America appea... more Fertilizer recommendations for producing shade trees in nursery field soil in North America appear to be based on tradition and tree performance; there is little empirical data. This study was designed to examine efficacy of reducing traditional or historical fertilizer amount (rate) and number of applications for two taxa and to present a protocol for growers to test fertilizer use efficiency. A traditional rate of fertilizer was applied along with four others: zero, one-third, two-thirds, or one-and-one-third traditional. Fertilizer was divided into one, two, three (traditional), or four equal amounts applied during the growing season. The study was conducted on a fine sand field soil with 680 trees of each taxa in adjacent plots of the same field. There were 16 factorial treatment combinations plus a non-fertilized control. Fertilizer rate cut to one-third of the historical rate, and number of applications reduced from three to either one or two, resulted in little if any reducti...
Propagation containers modify root systems, which affect post-planting anchorage in reforestation... more Propagation containers modify root systems, which affect post-planting anchorage in reforestation efforts, but little is known about larger-sized trees typical in urban landscapes. The main goal of this study was to determine the role of root morphology on postplanting anchorage and growth on Swietenia mahagoni (L.) Jacq., a common landscape tree in warm climates. Two propagation container types, two larger container types, and root pruning were used to impose various root morphologies inside root balls. Anchorage was evaluated by winching trees at two bending stresses to simulate wind events. Interaction between propagation container type and root pruning when the liner was shifted into 3.8 L containers prevented either from consistently influencing anchorage. Trunk tilt (i.e., instability) immediately following pulling was greatest for trees with the most root CSA deflected by the 9.5 L container; trees with straighter main roots in the root ball were better anchored. Researchers ...
Trees of live oak (Quercus virginiana Mill.) were container-grown (CG) or field-grown (FG) to a m... more Trees of live oak (Quercus virginiana Mill.) were container-grown (CG) or field-grown (FG) to a mean trunk diameter of 9.4 cm (3.7 in), transplanted into sandy soil, and established with frequent or periodic irrigation. Three years after transplanting, trees were harvested with a 1.5 m (60 in) diameter tree spade. Root number and root cross-sectional area was evaluated for all roots at the periphery of the tree-spade-dug root ball. Despite similar increases in trunk diameter, FG trees had greater root number and root cross-sectional area than CG trees. The greater root cross-sectional area occurred in roots 5–20 mm (0.2–0.8 in) in diameter at soil depths of 0–25 cm (0–9.8 in) and 75–100 cm (29.5–39.3 in). Irrigation frequency after transplanting had no effect on root number in FG trees. However, root number in CG trees was lower without frequent irrigation.
Irrigation placement and irrigation volume during field production of live oak (Quercus virginian... more Irrigation placement and irrigation volume during field production of live oak (Quercus virginiana Mill.) in a sandy soil had no effect on trunk caliper [mean = 6.3 cm (2.5 in)] or tree height [mean = 3.8 m (12.4 ft)]. Root pruning had no impact on caliper and a slight (P < 0.06) impact on height. Irrigation placement and volume had little effect on number of cut roots at the edge of the root ball. Root pruning with a hand spade or in combination with root-pruning fabric placed under the liner at planting increased the number of roots at the edge of the root ball. Root pruning with fabric in combination with spade pruning increased the small-diameter (<5 mm) root weight: shoot ratio but reduced the total root weight: shoot ratio. Irrigation placement and volume during production did not affect summer nor winter digging survival. Trees that were not root pruned had poorer survival in the summer and winter digging seasons than those receiving either of the root-pruned treatments...
Irrigation frequency and volume effects were evaluated on recently installed #3 container grown s... more Irrigation frequency and volume effects were evaluated on recently installed #3 container grown shrubs of three taxa, Ilex cornuta Lindl. & Paxt. ‘Burfordii Nana’, Pittosporum tobira Thunb. ‘Variegata’, and Viburnum odorotissimum Ker Gawl. Irrigation frequency and volume had no effect on Pittosporum at any time for any measured root or shoot parameter. Irrigation frequency and volume had no effect on Ilex and Viburnum canopy biomass, root biomass, root dry weight:canopy dry weight ratio, and stem water potential at any time after planting. Canopy growth was affected by irrigation treatment only for Viburnum plants installed in May 2004, and growth response to more frequent irrigation only occurred while plants were irrigated, with no lasting impact on growth once irrigation ceased. Root spread and root spread:canopy spread ratio for only one species, Ilex, were influenced by irrigation treatment. Applying excessive irrigation volume (in this case 9L) reduced root dry weight: shoot d...
Root form is governed by seedling genetics and soil characteristics including texture, compaction... more Root form is governed by seedling genetics and soil characteristics including texture, compaction, depth to the water table, fertility, moisture content and other factors. Trees develop lateral roots growing parallel to the surface of the soil. These are generally located in the top 30 cm (12 in) of soil. Fine roots emerge from lateral roots and grow into the soil close to the surface. If soil conditions permit, some trees grow tap and other vertically oriented roots capable of penetrating several feet into the soil. Many trees, particularly those planted in urban landscapes, do not generate tap roots. Lateral roots spread to well beyond the edge of the branches. Their growth in governed by competition from other plants, available water, soil temperature, fertility, stage of shoot growth and other factors.
Cultural factors influencing root growth in the landscape or nursery include soil management, irr... more Cultural factors influencing root growth in the landscape or nursery include soil management, irrigation, fertilization, shoot pruning and root pruning. These affect root density, depth of penetration, spread, vertical distribution in the soil profile and mineral uptake. Root morphology varies widely among genera, species and individuals within a species. The distribution, length and weight of roots within the root ball of transplanted field-grown trees can be modified with cultural management practices. Growth of transplanted trees may be affected by these modifications. Root spread diameter increases at a rate of 0.9–2.4 m (36–96 in)/year following planting. From 1 to 10 years is required to replace the pre-transplant root system for trees transplanted from field nurseries. Root system in urban environments can be modified by cultural techniques which direct their growth.
Roots of four-year-old, field-grown southern magnolia (Magnolia grandiflora L.) were pruned in 19... more Roots of four-year-old, field-grown southern magnolia (Magnolia grandiflora L.) were pruned in 1987 once during dormancy, following the first shoot growth flush or after the second growth flush, prior to transplanting in January 1988. By the end of the 1987 growing season, root pruning at all stages of growth reduced leaf number, tree height, trunk caliper, and total-tree leaf area and weight compared with unpruned controls. Total root weight was less for trees pruned during dormancy or following the first growth flush. Root pruning increased the proportion of fine roots (0 to 5mm-diameter class) to coarse roots (>5 to 10-mm diameter class). Shoot:root ratios were not affected by root pruning. During the first year after transplanting, root pruned trees grew at a slightly faster rate than unpruned trees but growth rates were similar for root pruned and unpruned trees the second and third year after transplanting. Trees required, at most, 1 year per inch of trunk caliper to become...
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