A 2-year study was conducted in southwest Florida to evaluate the effects of quick vs. slow-release nitrogen sources commonly used in landscapes on wound closure in live oak [Quercus virginiana (Mill.)]. Fertilized trees displayed nonsignificant shoot growth and leaf color when compared to nonfertilized ones. Neither fertilizer type, nor rate of application appeared to affect wound closure rates over the two year measurement period. This study showed increased replication will be needed when studying landscape trees, since trends in known primary growth response to fertilization were present but were not statistically significant. Fertilization effects on secondary growth including diameter increase and wound closure rate, were correspondingly not significant. Secondary growth responses may be difficult to demonstrate in live oak when using landscape trees especially at lower nitrogen rates currently being recommended in the industry.
). The objective of this research was to examine the impact of PBZ, when applied with root pruning, on the overall growth and vitality of field-grown live oak tree roots pruned at two distances from the tree. Materials and methods The research was
Live oak (Quercus virginiana Mill.) traditionally has been propagated by seed because vegetative propagation has not been successful on a commercial scale (Flemer, 1962; Maynard and Bassuk, 1987; Morgan and McWilliams, 1976). However, as a result of seedling variability, live oaks offered for sale exhibited varied growth forms with variable quality.
Stem cuttings taken from rooted propagules of a 2-year old South Texas live oak, Quercus virginiana Mill., and maintained for 2 years in a greenhouse rooted in greater numbers than did cuttings taken directly from the original tree 2 years later. Rooting of cuttings from trees 5-8 years decreased with tree age.
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.
Mature acorns of the live oak (Quercus virginiana Mill.) were immersed for 0-60 minutes in 43.3 to 60.0°C (110 to 140°F) water baths. Various of those treatments produced up to 100% control of larvae of acorn weevils (Curculio sp.) in the seeds, but reduced acorn germination and radicle length to varying degrees.
magnolia ( Magnolia grandiflora ) during the first year after planting, but treatment differences were significant after 3 and 4 years. On the other hand, fertilized live oak ( Quercus virginiana ) were larger than unfertilized trees during their first year
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.
Live oak (Quercus virginiana Mill.) acorns harvested for commercial seedling production frequently are heavily infested by larvae of Curculio spp. (2). Many nurserymen routinely soak acorns for 30 min in 49°C water to kill weevil larvae before planting the seed (4). Microwave radiation is effective against some stored products pests, but it is too damaging for use against acorn weevil larvae (2). Crocker and Morgan (1) measured the short-term (12-day) effects of hydrothermal treatments of tree-harvested acorns on survival of weevil larvae and seed germination, using 0- to 60-min immersion of the seed in 43.3° to 60.0° baths. Treatment for any of the tested times at a minimum of ≈49° controlled 100% of the weevils; it also produced dosage-related plant mortality and reduction in the short-term growth of seedlings. In the present research, we examined the survival and long-term vigor of acorns that were exposed to a 49° hydrothermal treatment.
Large (≈5 m high) Quercus virginiana Mill. (live oak) trees produced in 0.64-m-diameter in-ground fabric containers were root pruned or not root pruned inside containers before harvest. Harvested trees were grown in two sizes of polyethylene containers for 10 months, then transplanted into a landscape. Water potential (ψT) of small branches (<4 mm in diameter) was measured diurnally during containerization and for 1 year in the landscape. Root pruning had no influence on postharvest survival. Neither root pruning nor container size affected tree water status during containerization or in the landscape. All surviving trees recovered from transplant shock following harvest after 16 weeks in a container, independent of treatment. In the landscape, 35 weeks of daily irrigation were required before dusk ψT declined to within 0.1 MPa of predawn values, a result indicating alleviation of transplant shock. Trunk growth rate during containerization was highest in larger containers. However, in the landscape, root pruning and small containers were associated with higher trunk growth rate. Tree water status during containerization and in the landscape is discussed.