Quercus Virginiana Mill Research Articles

Root Pruning and Planting Depth Impact Root Morphology in Containers

Increasingly, producers and consumers are realizing that roots play a major role in nursery tree quality. To remain competitive, producers need to find economically viable methods of increasing quality standards. Two studies were designed to test methods of improving root systems in a container root ball. In the first, three different root pruning methods and two planting depths were imposed as 3.7 liter (1 gal) container-grown Royal poinciana [Delonix regia (Bojer) Raf.] and trumpet-tree [Tabebuia heterophylla (DC.) Britton] were shifted to 25 liter (6.6 gal) containers. Root pruning and planting depth had no impact on trunk caliper or tree height. Vertical root ball slicing or shaving off the periphery of the root ball increased the number of straight roots inside root balls and reduced the presence of deflected roots, but shaving had a greater effect and was associated with consistently high-quality root systems. Trees planted with the top-most root 10 cm (4 in) below the 25 liter (6.6 gal) container substrate surface had more deflected roots and fewer straight roots than trees planted with roots close to the surface. In the second study, teasing or shaving live oak (Quercus virginiana Mill. ‘SNDL’) in 3.7 liter (1 gal) container root balls resulted in identical root systems in 57 liter (15 gal) containers one year later, and both treatments resulted in higher quality root systems than trees not root pruned.

Root Pruning at Planting and Planting Depth in the Nursery Impact Root System Morphology and Anchorage

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 trees than those not root pruned at planting. Bending moment at 20 degrees trunk tilt was best correlated with cross sectional area of roots growing straight across the periphery of the root ball and into landscape soil.

Long-Term Effects of Fire, Livestock Herbivory Removal, and Weather Variability in Texas Semiarid Savanna

We examined how the occurrence and structure of grasses and woody plants changed after 12 yr of a fire season manipulation and removal of livestock herbivores. Applying high intensity fires in the summer preserved the structural integrity of this semiarid live oak (Quercus virginiana Mill.) savanna while decreasing or eliminating numerous problematic plants in the understory and overstory, such as prickly pear cactus (Opuntia spp.), sacahuista (Nolina texana S. Watson), Ashe juniper (Juniperus ashei J. Buchholz), Pinchot's juniper (J. pinchotii Sudw.), and honey mesquite (Prosopis glandulosa Torr.). In the less intense repeat winter burning treatments, undesirable woody plants were generally maintained at pretreatment levels in the overstory but all woody plants except Ashe juniper increased in the understory. Alternatively, areas excluded from fire in the control treatment rapidly transitioned from a grass-tree codominated savanna environment to one that is heavily dominated by woody plants. In the grass community, the most frequently occurring grass species in the winter burn treatment differed from summer burn and control treatments, whereas the summer burn treatment was not different from the control. Of the herbaceous plants, only little bluestem (Schizachyrium scoparium [Michx.] Nash) responded to fire treatments. Little bluestem increased in the winter burn treatment, remained fairly constant in the summer burn treatment, and decreased in the control. Other grasses varied largely as a function of annual weather variability, the removal of livestock, and legacy effects resulting from pre-existing variability. These findings suggest that fire can reduce or eliminate woody plant species that threaten the stability of live oak savannas while having little long-term effect on grasses desired by rangeland managers.

Evaluating the potential for dendrochronological analysis of live oak (Quercus virginiana Mill.) from the urban and rural environment—An explorative study

Live oak (Quercus virginiana Mill.) is a long lived, broadleaf, evergreen species native to the lower Coastal Plain of the southern and southeastern United States and is frequently planted in the urban environment. However, live oak has received limited attention for its potential for dendrochronological analyses possibly because its growth-ring boundaries may be less defined due to the absence of a distinct dormancy period. The objective of this explorative study was to determine whether live oak rings in both urban and historic trees could be accurately identified and measured for dendrochronological applications. One hundred urban live oaks were assessed as well as four cross-sectional specimens from historic sites in the southeastern United States. Age of all cored live oak ranged from 7 to 29 (average=16.8 rings), while cross-sections were taken from trees with an average age of 175 years. A chronology was created from cores that had the highest interseries correlations (n=27), resulting in an average interseries correlation of 0.654. The analysis of live oak cross sections revealed that the rings on live oak are very faint and barely discernible, delimited mainly by a faint row of earlywood vessels with no or barely visible terminal parenchyma. Rings on these sections were erratic (i.e., fading out along the circumference) and non-concentric (i.e., a particular ring could be both wide and narrow at certain points along the circumference) so that any attempt to measure the rings on opposing radii would have produced meaningless results. However, based on the results of this study, we conclude that the dendrochronological analysis of live oak is possible with careful sample preparation and analysis and that results would be reliable, even for urban trees. Results of this study suggest that urban tree-ring series with higher interseries correlations were more vigorous than those with lower values, suggesting that urban environmental stresses related to individual sites may decrease the usefulness of crossdating techniques for evaluating annual rings on younger, urban trees.

Planting depth and soil amendments affect growth of Quercus virginiana Mill.

The effect of planting depth, defined as the location of the root collar relative to soil surface, is of particular concern for tree growth, development, and performance in the landscape and seems to be dependent on soil conditions. The objective of this study was to determine the effect of three planting depths and four soil amendments on live oak ( Quercus virginiana Mill.) growth and visual quality. Trees were planted with root collars at one of three planting depths (grade, 7.6 cm above grade, or 7.6 cm below grade). Soil amendments were: incorporated sand (30% by volume), incorporated composted peat (30% by volume), sandy topsoil in raised (20 cm) bed, and native sandy loam soil (control). Planting at grade or below grade resulted in 0% mortality, while planting live oak trees above grade resulted in 12.5% mortality. The container produced trees were top-heavy (high shoot:root ratio) and were thus susceptible to wind damage when planted above grade. Trunk diameter growth and relative growth rate were smaller when trees were planted with root collars below grade compared to those planted above grade or at grade. Visual quality of live oak roots was improved when trees were planted in raised beds with sandy topsoil compared to the control soil. Shoot visual quality was improved when trees were planted in the incorporated sand and raised beds with sandy topsoil compared to the control and incorporated peat sections. Thus, it is recommended to plant live oaks with the root collar at grade and in sandy top soils in raised beds to improve tree quality after establishment.

Quercus virginiana root attributes and lateral stability after planting at different depths

Planting depth and irrigation can impact root and trunk growth following landscape installation in various soil types; however, impact on lateral tree stability is unknown. Quercus virginiana Mill. trees were installed at four landscape planting depths into a well drained sandy soil and grown for six years under two irrigation regimes. There was no impact of planting depth on trunk diameter or height in the first five growing seasons after planting; however, trees irrigated regularly had 10 mm larger trunk diameter than trees not irrigated. There was no impact of planting depth or irrigation on bending stress required to tilt trunks to 1°, 2° and 5° from vertical non-deformed start position six growing seasons after planting. Planting depth and irrigation also had no effect on diameter of the ten largest roots to a soil depth of 122 cm, which might explain why bending stress required to pull trees was similar for all planting depth and irrigation treatments. However, trees planted deeper had deeper roots measured 115 cm horizontally from trunk. Root cross-sectional area (CSA) 20–30 and 40–50 cm deep was positively correlated with bending stress six growing seasons after planting. Trees planted deep had some roots that ascended toward soil surface at a steeper angle than trees planted shallow, and had a deeper root flare and more roots growing over the flare that could potentially form stem girdling roots. Diameter of roots over the flare was not impacted by planting depth; however, trees irrigated for the duration of the study had more roots over main flare roots than trees not irrigated. Irrigation increased root number (>5 mm diameter) in the top 30 cm soil profile. Irrigation had no impact on any other measured root parameter. Trees planted deeper settled down below soil surface more than shallow planted trees.

Effect of Fabric and Plastic Containers on Plant Growth and Root Zone Temperatures of Four Tree Species

Abstract Live oak (Quercus virginiana Mill.), red maple (Acer rubrum L.), and sweet gum (Liquidambar styraciflua L.) trees were planted in #7 fabric or plastic containers on April 18, 2004, and grown for two growing seasons. Live oak and golden rain tree (Koelreuteria paniculata Laxm.) trees were planted in #10 fabric or plastic containers on May 6, 2005, and harvested the following summer. Plant height, canopy width, and caliper were measured periodically, and root zone temperatures were recorded at 30-min intervals throughout each study. In the 2004 planting, live oak height and canopy width increased more for plants in plastic containers than for those in fabric containers from May to July 2004. In contrast, no difference in live oak height or canopy width growth occurred between container types from July to September 2004, but trunk caliper increased more in plastic than in fabric containers during this time interval. No differences between container treatments were noted for any measured parameter for red maple or sweet gum trees planted in 2004 or for golden rain tree or live oak trees planted in 2005 at any measurement interval during the study. Average monthly high and low substrate temperatures were similar between the two container types throughout the study. Fabric containers appear to be a reasonable alternative to plastic containers for above ground nursery crop production, although small differences in growth occur for some species.

First Report of Soybean Rust Caused by Phakopsora pachyrhizi on Erythrina herbacea (Coral Bean).

Soybean rust (SBR), caused by the obligate fungus Phakopsora pachyrhizi Syd. & P. Syd., was initially reported on soybean (Glycine max L.) in Louisiana in 2004 and has since been reported on soybean and/or kudzu (Pueraria lobata (Willd.) Ohwi) in 9 states in 2005, 15 states in 2006, and 19 states in 2007 (1). The host range of P. pachyrhizi includes plants that are all in the Fabaceae or legume family. Six plant species in the United States have been reported as hosts of P. pachyrhizi: soybean, kudzu, Florida beggarweed (Desmodium tortuosum (Sw) DC.), dry bean (Phaseolus vulgaris L.), lima bean (P. lunatus L.), and scarlet runner bean (P. coccineus L.) (4). On 17 April 2008, a rust disease was observed on a weedy legume host with red showy flowers that was growing with kudzu in an overgrown vacant lot in the understory of live oak trees (Quercus virginiana Mill.) in Citra, FL. The discovery was made during routine scouting of this Integrated Pest Management Pest Information Platform for Extension and Education (IPM PIPE) mobile sentinel plot (3). The plant was confirmed by University of Florida botanists to be Erythrina herbaceae L., commonly known as coral bean. Coral bean is native to the southeastern United States and also is planted as a perennial ornamental. A sample of leaves exhibiting rust pustules characteristic of P. pachyrhizi uredinia was collected and examined with a microscope. Brown-to-brick red, angular lesions that were 3 to 11 mm in diameter (average 6.75 mm) were observed on the undersides of the leaves of two trifoliates. Within these lesions, there were several uredinia, some exuding hyaline, echinulate urediniospores (20 × 25 μm). The visual diagnosis and the species of the rust fungus were confirmed to be P. pachyrizi by a real-time PCR protocol (2). The diagnosis on this new host was verified by a USDA, APHIS National Mycologist in Beltsville, MD. Coral bean may serve as an additional overwintering host for P. pachyrhizi in the southeast. To our knowledge, this is the first report of soybean rust caused by P. pachyrhizi on E. herbaceae.

Use of branch cross-sectional area for predicting pruning dose in young field-grown Quercus virginiana ‘Cathedral’ in Florida, US

Allometric relationships for trunk, first order branches and associated foliage were developed to develop a repeatable pruning dose for wind interception studies on Quercus virginiana Mill ‘Cathedral’. Three trees were dissected to develop relationships. It was determined that leaf mass was linearly related to the basal area of the primary branch, consistent with pipe model expectations. A pruning dose for leaf mass removal was defined by tracking basal branch areas and removing entire first order branches. Leaf mass was closely related to leaf surface area, however leaf mass varied with compass orientation while leaf area remained unchanged. The use of wood cross-section area conservation rules for branching in Lindenmayer (L-system) computer modeling is shown to be inconsistent with the data set, as is often observed in the field. The area conservation assumption is made to force taper into computer models, and departures are accepted by assuming heartwood formation forces imbalance into the model. The data set was developed from 3 year old or younger wood. The species is known to retain viable vessel elements in sapwood for at least 3 years in the areas surrounding the testing site. Since it is doubtful that there was heartwood or non-functional sapwood in the test trees, use of the area balance assumption for modeling by asserting heartwood influence is questionable.

Atmospheric and soil drought reduce nocturnal conductance in live oaks

Nocturnal and daytime whole-canopy transpiration rate (E) and conductance (g = E/VPD, where VPD is leaf to air vapor pressure difference) were assessed gravimetrically in drought-treated and well-watered 3-year-old saplings of live oak species (Quercus series Virentes Nixon) from the southeastern USA (Quercus virginiana Mill.) and Central America (Q. oleoides Cham. and Schlecter). Our objectives were to: (1) quantify nocturnal and daytime E and g in a controlled environment; (2) determine the impact of severe drought on nocturnal E and g; and (3) examine whether unavoidable water loss through the epidermis could account for nocturnal water loss. We calculated daytime E during peak daylight hours (between 0930 and 1330 h) and nocturnal E during complete darkness (between 2200 and 0500 h). In addition to reducing E and g during the daytime, drought-treated plants reduced nocturnal E and g on a whole-canopy basis by 62-64% and 59-61%, respectively, and on a leaf-level basis by 27-28% and 19-26%, respectively. In well-watered plants, nocturnal g declined with increasing VPD, providing evidence for stomatal regulation of nocturnal transpiration. In drought-treated plants, g was low and there was no relationship between nocturnal g and VPD, indicating that water loss could not be reduced further through stomatal regulation. Both daytime and nocturnal g declined curvilinearly with predawn water potential for all plants, but nocturnal g was unrelated to predawn water potentials below -1 MPa. The reductions in daytime and nocturnal E and g during drought were associated with decreases in whole-plant and leaf hydraulic conductances. Observed nocturnal g was within the same range as epidermal conductance for oak species determined in previous studies under a range of conditions. Nocturnal E rose from 6-8% of daytime E for well watered plants to 19-20% of daytime E for drought-treated plants. These results indicate that, during drought, saplings of live oak species reduce g to a minimum through stomatal closure, and experience unavoidable water loss through the epidermis.

Pruning Lower Branches of Live Oak (Quercus virginiana Mill.) Cultivars and Seedlings during Nursery Production: Balancing Growth and Efficiency

Abstract Tree production requires time for pruning to meet customer expectations, yet pruning can slow growth and increase the time (and cost) to prepare trees for market. Our research quantifies trade-offs between growth and pruning. In two separate locations, over two time periods, we found no difference in caliper growth between trees with only the largest one or two low branches removed at each pruning, compared with trees having all lower branches shortened. Acorn-propagated and Cathedral Oak® Quercus virginiana (Mill.) with all branches removed from the lower 1.37 m (4.5 ft) of trunk (temporary branches destined to be removed to produce a trunk clear of branches and a distinct canopy) by 18 months after planting had smaller caliper than other pruning treatments; however, pruning these branches had no impact on the Highrise® cultivar. Removing the largest one or two low branches at each pruning was the most efficient pruning method tested. Removing all temporary branches in February of the last year of production (2004) did not reduce caliper, height, or canopy spread compared to removing half in February and half in October. Since there was no difference in time required for pruning, we suggest removing branches early in the last growing season for more completely closed wounds and enhanced customer appeal.

ADULT PHYLLOPHAGA EPHILIDA HOST PLANT FEEDING PREFERENCE

Abstract Limited biological information about Phyllophaga ephilida, a major sweet potato pest in Louisiana, is available. In 2001 and 2002, a study was conducted in the laboratory to investigate the feeding preference of adult Phyllophaga ephilida (Say) (Coleoptera: Scarabaeidae) for the foliage of eight woody plant species: water oak (Quercus nigra L.), live oak (Quercus virginiana Mill.), red maple (Acer rubrum L.), slash pine (Pinus caribaea Morelet), pecan (Carya illinoensis (Wangenh) K. Koch), sweetgum (Liquidambar styraciflua L.), southern magnolia (Magnolia grandiflora L.), and American elm (Ulmus americana L.). Beetles were placed in an arena with the eight host plants and allowed to feed for 24 h (choice test). Leaf area consumed and change in leaf weight were recorded. In 2001 and 2002, host plant had a significant effect on both leaf area and weight consumed. In 2001, mean leaf area (mm2) consumed was pecan (504), followed by elm (314), water oak (237), maple (176), live oak (38.0), and sweetgu...

Long-Term Growth of Live Oak Propagated from Rhizomic Shoot Cuttings or Seeds

Abstract Rhizomic shoot cuttings of live oak (Quercus virginiana Mill.) were taken from a single tree about 50 years old in late August 1990, rooted, and planted into 2.6 liter (#1) plastic pots. Concurrently, acorns were collected from the same tree and germinated. Trees from both sources were planted into 13 liter (#5) plastic pots in July 1991 and then to the field in July 1992 either directly in the ground, in 37 or 46 cm (14 and 18 in) diameter polypropylene fabric bags buried in the ground, or in 13 liter pots (#5) placed on the surface. Trunk circumference 10 cm (4 in) above the soil line was measured yearly between 1993 and 1999. Initially, trees from rhizomic shoot cuttings grew slower than seedlings based on trunk circumference, diameter, and cross-sectional area. However, there were no statistical differences after 1996 in trunk circumference, diameter and cross-sectional area between the trees propagated from rhizomic shoot cuttings and seeds. Only in 1993, trees in 37 cm (14 in) bags and plastic pots had greater growth than trees in the ground. About one-third of the seedling trees produced rhizomic shoots in comparison to none of the trees from rhizomic shoot cuttings.

Anti-quorum sensing activity of medicinal plants in southern Florida

Bacterial intercellular communication, or quorum sensing (QS), controls the pathogenesis of many medically important organisms. Anti-QS compounds are known to exist in marine algae and have the ability to attenuate bacterial pathogenicity. We hypothesized that terrestrial plants traditionally used as medicines may also produce anti-QS compounds. To test this hypothesis, 50 medicinal plants from southern Florida were screened for anti-QS activity using two biomonitor strains, Chromobacterium violaceum and Agrobacterium tumefaciens. Of these plants, six showed QS inhibition: Conocarpus erectus L. (Combretaceae), Chamaecyce hypericifolia (L.) Millsp. (Euphorbiaceae), Callistemon viminalis (Sol. ex Gaertn.) G. Don (Myrtaceae), Bucida burceras L. (Combretaceae), Tetrazygia bicolor (Mill.) Cogn. (Melastomataceae), and Quercus virginiana Mill. (Fagaceae). This study introduces not only a new mode of action and possible validation for traditional plant use, but also a potentially new therapeutic direction for the treatment of bacterial infections.

New Genera, New Species, and New Combinations in Western Nearctic Phylini (Heteroptera: Miridae: Phylinae)

Six new genera and six new species of Phylinae are described from the western United States and Baja California, Mexico, and two new combinations are created. Most of the species are known to breed on oaks, Quercus spp. (Fagaceae). Galbinocoris caepa, new genus and species, is described from Arizona and Texas. Hamatophylus, new genus, is described to accommodate Plagiognathus guttulosus (Reuter), which breeds on several species of oaks, among them Quercus virginiana Mill. Insulaphylus, new genus, is restricted to the Channel Islands off the coast of southern California, and is described to accommodate Insulaphylus cruz, new species, from Santa Cruz Island and Insulaphylus meridianus, new species, from Santa Catalina and San Clemente Islands. Both species breed on Quercus spp. Maculamiris, new genus, is described with two species, Maculamiris baja, new species, from Baja California and southern California, and Maculamiris insulanus, new species, from the Channel Islands. Both species are associated with rosaceous plants. Quernocoris caliginosus, new genus and species, is described from mainland southern California and the Channel Islands where it breeds on a range of oak species. Vesperocoris, new genus, is described to accommodate the often oak-breeding Plagiognathus paddocki Knight from California.

(168) Long-term Growth of Live Oak from Seed or Cutting

Live oak trees raised from acorns are highly non-uniform and many produce numerous undesirable rhizomic shoots. The objectives of this study were to 1) compare the growth rates between (Quercus virginiana Mill.) trees from seed and cutting in four production systems and 2) determine if trees from cuttings produce rhizomic shoots. Rhizomic shoot cuttings 25–30 cm long were taken from a single tree about 50 years old in late Aug. 1990, rooted, and planted in 2.6-L pots after 2 months. During the same week, acorns were collected from the same tree and germinated. All trees were planted into 13-L pots in July 1991 and then to a field in July 1992. Trees from both sources were planted either directly in the ground, in 36.6- or 45.7-cm-diameter polypropylene fabric bags buried in the ground, or in 13-L pots on the ground. Trunk circumference 10 cm above the soil line was roughly measured yearly between 1992 and 1999. Initially, trees from cuttings grew slightly slower than seedlings, having a smaller trunk circumference, diameter, and cross-sectional area. These differences diminished and all trees had similar circumferences after 1996. In 1992, trees in 36.6-cm bags and pots had more growth than trees in the ground. In 1993, trees in pots had better growth than those in the ground. After 1993, all trees had similar circumferences until the end of this study, probably due to roots extending beyond the bags and pots into the surrounding soil. About one-third of the seedling trees produced rhizomic shoots, whereas none of the trees from cuttings did. The rhizomic shoots of trees in pots were contained within the pot and none from the ground. Another significance of this research is that the cloned trees from cuttings were extremely uniform in growth habit and form.

(116) Short-term Responses of Live Oak to Planting Depth and Soil Amendments

Tree transplanting practices influence plant survival, establishment, and subsequent landscape value. However, transplanting practices vary substantially within the horticultural industry. Of particular importance is the location of the root collar relative to soil grade at transplant. The objective of this study was to determine the effects of factorial combinations of planting depths, root collar at grade or 7.6 cm either above or below grade, and soil amendments on container-grown (11 L) Quercus virginiana Mill. Soil treatments included a tilled native soil (heavy clay loam, Zack Series, Zack-urban land complex, fine, montmorillonitic, thermic, udic paleustalfs), native soils amended with 7.6 cm of coarse blasting sand or peat that were then tilled to a depth of 23 cm, or raised beds containing 20 cm of sandy loam soil (Silawa fine sandy loam, siliceous, thermic, ultic haplustalfs). A significant (P ≤ 0.05) block by soil amendment interaction occurred for photosynthetic activity. Incorporation of peat significantly decreased the bulk density of the native soil. Planting depth had no significant effect on photosynthetic activity or stem xylem water potential at 3 months after transplant. Soil water potentials did not statistically differ among treatments.

Effect of drought on isoprene emission rates from leaves of Quercus virginiana Mill.

Leaf isoprene emission rates ( F iso ) were studied in 2-year old trees of live oak ( Quercus virginiana Mill.) during two drying–rewatering cycles. During the first drying–rewatering cycle, photosynthesis ( A ) and stomatal conductance ( g s ) decreased by 92%(±7%) and 91%(±8%), respectively, while F iso remained essentially constant for 8 days of treatment. After 12 days under severe drought conditions, F iso was reduced by 64%(±6%). Similar values were found during the second drying–rewatering cycle. During the recovery phase of both cycles, F iso recovered more quickly than A and g s . The lower drought sensitivity of F iso compared with that of A resulted in a higher percentage of fixed C lost as isoprene ( C iso / C A ) as plants became more stressed, reaching peaks of 50% when A was almost zero. F iso showed a strong negative linear relationship with pre-dawn leaf water potential ( ψ PD ) that could be a useful parameter to include in isoprene emission models to account for effects of drought stress on leaf F iso .

Effects Of Amendments, Soil Additives, And Irrigation On Tree Survival And Growth

During the first and second year after transplanting into good soil, there was no apparent benefit from adding amendments to the backfill soil around newly planted 5 cm (2 in.) caliper live oaks (Quercus virginiana Mill.), nor was there a benefit from applying liquid additives over the root ball. Top growth in the first 2 years after planting was not enhanced on trees with amendments added to the backfill soil compared to the control. In the first growing season following planting, trees irrigated frequently (3 times per week for 38 weeks) grew about twice as fast as those irrigated only during the first 3 months after planting. There was no lingering effect of irrigation on top growth rates once irrigation ceased. Trunk diameter and height growth on trees treated with paclobutrazol (Profile 2SC) was less than on trees in all other treatments due to the growth-regulating effect of paclobutrazol. Root growth in the backfill soil was not affected by soil amendments added to the backfill soil at planting and was not affected by irrigation after planting in 5 of the 7 treatments.

Mulch And Planting Depth Affect Live Oak (Quercus Virginiana Mill.) Establishment

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 intercepted water, resulting in more tree stress and greater likelihood of tree death in the first 4 weeks after planting. However, trees planted deeply were less stressed 3 months after planting. No root ball settlement occurred in the first 6 months after planting container-grown trees.