bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling Transpiration from Selected Urban Shade Tree Species
Authors: Vrecenak A.J. , Herrington L.P.
Published: August 2020

A computer model of transpiration from individual tree crowns was modified, tested and verified using container-grown Norway maple (Acer platanoides) and sugar maple (Acer saccharum), two widely planted street trees in the Northeastern United States. Within each species, three soil moisture regimes were established to simulate non-drought stressed, moderately drought stressed and severely drought stressed conditions. Model estimates of transpiration were compared to lysimetric determinations as a verification of the model's ability to simulate the transpirational process. Model estimates of average hourly transpiration rates ranged from 6.8 to 55.5 g/m2/hr (0.24 to 2.00 oz/yd2 of leaf surface/hr) while lysimetric determinations ranged from 10.4 to 63.4 g/m2/hr (0.37 to 2.28 oz/yd2 of leaf surface per hour). The success of the model as a mechanistic simulation of transpiration, its areas of weakness and the need for further research to strengthen the model are discussed.
Effect of Harvest Method on Seed Yield of Coreopsis lanceolata L. and Gaillardia pulchella Foug.
Authors: Norcini Jeffrey G. , Aldrich James H. , Martin Frank G.
Published: August 2020

Seed of north Florida ecotypes of lanceleaf coreopsis (Coreopsis lanceolata L.) and blanketflower (Gaillardia pulchella Foug.) were sown in February 1998 and harvested manually or mechanically (portable seed stripper) at two different times during the growing season. Mechanical harvesting of both species was more efficient based on the length of harvesting time relative to the yield of clean seed but hand harvesting yielded substantially more clean seed. Date of harvest (mid-July or early October) had several significant effects on blanketflower yield and quality. The July harvest resulted in 67% higher clean seed yield, 45% higher clean seed yield rate (a measure of harvesting efficiency), 9% greater seed mass, and 95% greater germination rate than the October harvest. Date of harvesting for lanceleaf coreopsis (late June and late August) had minimal effects on clean seed yield or quality.
Thidiazuron Increases Shoot Formation in Nandina
Authors: Keever Gary J. , Findley Douglas A.
Published: August 2020

A study conducted from 1997 to 2000 determined the effects of thidiazuron (TDZ) on shoot formation, whole plant size, and phytotoxicity in Nandina domestica Thunb. ‘Harbour Dwarf’ and ‘Compacta’ (2000 only). Single foliar applications of up to 4000 ppm TDZ increased shoot formation in both cultivars, with minimal effect on plant size or appearance. Single substrate drenches of up to 2500 ppm TDZ increased shoot formation in ‘Harbour Dwarf’ nandina but were severely phytotoxic, often resulting in foliar distortion and necrosis, or plant death.
Postemergence Prostrate Spurge (Chamaesyce prostrata) Control in Container-Grown Liriope
Authors: Altland James E. , Gilliam Charles H. , Olive John W.
Published: August 2020

Four experiments were conducted to evaluate herbicides for postemergence prostrate spurge (Chamaesyce prostrata (syn. Euphorbia prostrata)) control and tolerance of container-grown liriope (Liriope muscari). In Experiment 1, Manage, Image, Trimec Southern, and Roundup were applied at three rates each to single bib liners of ‘Big Blue’ liriope in 10.2 cm (4 in) pots. Pots were infested with prostrate spurge that were 1 to 2 cm (0.4 to 0.8 in) wide with no flower or seed structures. Only Roundup at 0.45 kg ai/ha (0.4 lb ai/A) provided effective postemergence spurge control (96%) and caused no short-term or long-term injury to ‘Big Blue’. In Experiment 2, Finale and Roundup were applied at three rates each to established ‘Big Blue’ in 3.8 liter (1 gal) containers. By 21 DAT, Finale at rates of 0.28 kg ai/ha (0.25 lb ai/A) or greater caused slight though significant injury to ‘Big Blue’ while Roundup caused no injury. No injury was observed on any plant at 60 DAT and the following spring, growth was similar among all treatments indicating no long-term effects. In Experiment 3, Finale and Roundup applications were made to recently divided liners of ‘Variegata’ liriope infested with mature spurge 17.0 to 20.1 cm (6.7 to 7.9 in) wide, which were flowering and seeding. Finale at 1.12 kg ai/ha (1.0 lb ai/A) and Roundup at 1.8 kg ai/ha (1.6 lb ai/A) provided effective spurge control (100 and 92.8%, respectively) and caused no short-term or long-term injury to ‘Variegata’. Lower rates were not effective in controlling mature spurge. In Experiment 4, Finale and Roundup were applied to recently divided liners of ‘Big Blue’ infested with mature spurge 23 to 31 cm (9.1 to 12.2 in) wide, which were flowering and seeding. At 21 DAT, Finale at 1.12 kg ai/ha (1 lb ai/A) and Roundup at 1.8 kg ai/ha (1.6 lb ai/A) provided 100% control, while lower rates of both herbicides provided poor control (14 to 85%). Both herbicides caused slight initial injury to ‘Big Blue’, however, injury was outgrown by 60 DAT and by the following spring all plants were similar in size and number of new bibs produced compared to non-treated controls.
IBA, Juvenility, and Position on Ortets Influence Propagation of Carolina Buckthorn from Softwood Cuttings
Authors: Graves William R.
Published: August 2020

Carolina buckthorn (Rhamnus caroliniana Walt.) has horticultural potential but is not often propagated or grown as a nursery crop. My objective was to determine how three concentrations of indolebutyric acid (IBA) affect foliar quality of cuttings, callus development, and rooting of terminal and subtending softwood cuttings from both juvenile and mature stock plants (ortets). Twelve cuttings were assigned to each of 12 factorial treatment combinations and held under intermittent mist for five weeks. Fewer than 10% of cuttings not treated with IBA rooted. Rooting ≥75% resulted when IBA at 3 or 8 g/kg (3000 or 8000 ppm) was applied unless the cuttings were from terminal positions on mature ortets. High quality and dry weight of leaves were associated with subtending cuttings that were juvenile and with terminal cuttings that were mature, but these foliar traits did not lead to particularly high rooting percentages. Juvenile cuttings with IBA at 8 g/kg (8000 ppm) formed the most primary roots and developed root systems with the greatest weight, and dry weight of roots on juvenile cuttings that were subtending (25.6 mg) was about four times that ofjuvenile, terminal cuttings (6.5 mg). The longest individual roots were on juvenile cuttings with IBA at 3 or 8 g/kg (3000 or 8000 ppm). Frequency of callus on the cut end of stems decreased as IBA concentration increased and was 94 and 75%, respectively, for cuttings from juvenile and mature ortets. Nearly all cuttings with IBA at 3 or 8 g/kg (3000 or 8000 ppm) developed callus on wounds that had been made along the sides of their stems. The frequency of side callus was greater for juvenile, subtending cuttings than for juvenile, terminal cuttings; the opposite was true for mature cuttings. These results confirm the sensitivity of stem cuttings of Carolina buckthorn to IBA. The data also demonstrate that use of subtending wood will improve rooting percentages of cuttings from mature ortets, and that use of subtending cuttings from juvenile plants and of IBA at 8 g/kg (8000 ppm) will increase the number and dry weight of roots.
Expanded Polystyrene as a Substitute for Perlite in Rooting Substrate
Authors: Cole Janet C. , Dunn Diane E.
Published: August 2020

Stem cuttings of rose-of-sharon (Hibiscus syriacus L. ‘Jeanne d'Arc’), barberry (Berberis thunbergii DC. ‘Crimson Pygmy’), juniper (Juniperus horizontalis Moench. ‘Plumosa Compacta’), and arborvitae (Thuja occidentalis L. ‘Woodwardii’) were rooted in substrates consisting of 0%, 25%, 50%, 75%, or 100% (by vol) perlite or expanded polystyrene beads with peat. Percentage of rose-of-sharon cuttings rooted and root ratings were lower with polystyrene than with perlite. Statistically, more barberry cuttings rooted with polystyrene (78.8%) than with perlite (78.3%), but the difference in rooting between polystyrene and perlite was not horticulturally significant. More juniper and arborvitae cuttings rooted with 50% perlite than with other perlite concentrations. Percentage of rooted juniper cuttings decreased but percentage of rooted arborvitae cuttings increased as polystyrene concentration in the substrate increased. More roots and longer roots formed on juniper cuttings with perlite than with the same concentration of polystyrene in the substrate. In contrast, arborvitae cuttings had more roots with 25% perlite than with 25% polystyrene, but arborvitae cuttings in 50%, 75%, or 100% polystyrene had more roots than cuttings in the same concentration of perlite. Results indicate expanded polystyrene is a reasonable substitute for perlite in rooting substrate for barberry, juniper, and arborvitae if appropriate ratios of polystyrene to peat are used.
Date of Potting and Fertilization Affects Plant Growth, Mineral Nutrient Content, and Substrate Electrical Conductivity
Authors: Ivy R. Lee , Bilderback Ted E. , Warren Stuart L
Published: August 2020

The landscape industry uses containerized plant material throughout the year. Thus, traditional spring potting at many nurseries has changed to potting throughout the year. The objective of this study was to determine the effect of potting date and rate of fertilization on plant growth and mineral nutrient content, substrate electrical conductivity (EC) and pH, and winter injury. To complete this objective, rooted stem cuttings of Ilex crenata Thunb. ‘Compacta’ and Viburnum awabuki K. Koch. ‘Chindo’ were potted in Raleigh, NC, July 17, 1998; September 7, 1998; October 29, 1998; March 25, 1999; and May 13, 1999. Two controlled-release fertilizers [Wilbro/Polyon 15N–1.8P–7.5K (15N–4P2O5–9K2O) and Scotts 23N–1.8P–6.6K (23N–4P2O5–8K2O)] were applied at four rates: a split application with 0.5X incorporated at potting and surface application of the remaining 0.5X six months after potting date [X = manufacturers' recommended rate per 3.8 liter (4 qt) container], and 1X, 1.5X, and 2X incorporated at potting. Plant growth and mineral nutrient content were determined one year after initial potting date. Substrate EC and pH were measured monthly. ‘Compacta’ holly and ‘Chindo’ viburnum potted in September or October were larger than plants potted in March regardless of fertilizer and rates of fertilization. In general, holly and viburnum were smaller when fertilized with 0.5/0.5X compared to 1X regardless of fertilizer and date of potting. Within each rate of fertilization, viburnum potted in September had significantly greater N and P content compared to viburnum potted in March or May. Nitrogen and P content were highly correlated to plant dry weight (r > 0.79, P = 0.0001). Mineral nutrient content of holly responded similarly. No plants were injured by winter temperatures regardless of potting date or rate of fertilization throughout the study period. Plants potted in July, September, or October had the highest substrate EC values in March, whereas plants potted in March or May had highest EC values in August regardless of species, fertilizer or rate of fertilization. Substrate pH was unaffected by date of potting, but pH decreased with increasing rates of fertilization.
Comparison of the Cold Hardiness of Landscape Tree and Shrub Cultivars Growing at Two Disparate Geographic Locations
Authors: McNamara Steve , Pellett Harold , Florkowska Malgorzata , Lindstrom Orville
Published: August 2020

The stem cold hardiness of 5 tree and 5 shrub cultivars was evaluated monthly from September 1998 through April 1999 on plants growing both at Griffin, GA (33° 15′ N), and Chanhassen, MN (44° 50' N), to determine whether cultivar hardiness varied with latitudinal differences in photoperiod and temperature conditions. On September 22, hardiness levels of five of the ten cultivars growing in Georgia were greater than or equal to those of their counterparts growing in Minnesota. After this date, however, all cultivars acclimated much more slowly in Georgia than in Minnesota, with the site-related hardiness differential on November 11 ranging from 13C (23F) for ‘Cully’ river birch to 25C (45F) for ‘Sunrise’ forsythia. The forsythia cultivars ‘Lynwood Gold’ and ‘Spring Glory’ were seriously injured in the Minnesota planting in early January when outdoor minimum temperatures were between−28 and−31C (−18 and−24F) for several days. All other taxa attained their maximum detected cold hardiness levels by January 13 in Minnesota, while some in Georgia continued to harden through February 10. With the exception of ‘Tristis’ weeping willow, all of the cultivars attained greater midwinter hardiness levels in Minnesota than in Georgia. All cultivars deacclimated much more rapidly in Georgia than in Minnesota. These results indicate that rates of cold acclimation and deacclimation and maximum midwinter hardiness levels of temperate zone woody plant taxa are strongly influenced by local photoperiod and temperature conditions. To accurately evaluate the geographic range of adaptability of woody plant taxa, cold hardiness evaluations need to be conducted regionally on locally grown plants.
Evaluation of Insecticides for Control of Larvae of Pyrrhalta Viburni, a New Pest of Viburnums
Authors: Weston Paul A. , Eshenaur Brian , Baird Joel M. , Lamboy Jana S.
Published: August 2020

Pyrrhalta viburni (Paykull), a newly introduced pest of viburnums in the United States, causes extensive defoliation, and eventually death, of a number of species of Viburnum commonly used in managed landscapes and occurring in native habitats. We evaluated several foliar and systemic insecticides for their ability to control the larvae of this leaf-feeding pest. Several foliar insecticides (Conserve SC, Dursban, and Pyronyl Crop Spray) significantly reduced defoliation by larvae, but the most effective products were two systemic insecticides (Merit and Meridian) that were applied before egg hatch. The ability of the soil-applied systemic products to be translocated throughout the plant, to remain active for very long durations (a year or longer), and to have minimal impact on foliar-dwelling natural enemies make them well suited for managing this pest until more sustainable forms of control can be developed.
Evaluation of Selected Bactericides for the Control of Fire Blight on Crabapple
Authors: Hagan A. K. , Akridge J. R.
Published: August 2020

Agrimycin 17 21.2W (streptomycin sulfate), Aliette WDG (fosetyl-Al), Kocide 101 77W (copper hydroxide), Phyton 27 (copper sulfate pentahydrate), and the experimental fungicide fluazinam 500F were evaluated for the control of fire blight (Erwinia amylovora) on field-grown crabapple. A block of bare-root flowering crabapple (Malus sp.) ‘Snowdrift’ was established in 1995, and the study was conducted in 1996, 1997, and 1998 at the Brewton Experiment Field in Brewton, AL (USDA Plant Hardiness Zone 8a). In all three years, streptomycin sulfate was the only product that significantly reduced the severity of fire blight. Typically, damage on the Agrimycin 17-treated trees was unobtrusive and restricted to the death of a few scattered bloom clusters (strikes). In two of three years, fire blight damage levels on the Kocide 101-treated trees were intermediate between those sprayed with streptomycin sulfate and the unsprayed control. Although intermediate disease control was also obtained in 1996 with Phyton 27, this fungicide/bactericide failed to significantly reduce disease severity in 1997 and 1998 as compared to the unsprayed control. In all three years, no significant reduction in the severity of fire blight was obtained with Aliette WDG or fluazinam 500F.
Bagworm Survival and Feeding Preferences as Indicators of Resistance among Maples
Authors: Klingeman William E.
Published: August 2020

The bagworm (Thyridopteryx ephemeraeformis (Haworth)) is a polyphagous, native pest of numerous deciduous and evergreen ornamental plants. Bagworm larvae were used to investigate host plant susceptibility among ten species and cultivars of maples that are economically important and commonly encountered in landscapes in the eastern United States. Data analyses from 48-hour choice assays, conducted in the laboratory during 2000 and 2001, indicated that differences existed among maples for bagworm feeding preferences and host plant susceptibility. Results from the 48-hour trials were not as accurate as seasonal no-choice assays, however. No-choice assays during both seasons quantified resistance among maples that limited larval bagworm survival and development. Measurements of larval feeding injury demonstrated resistance in paperbark maple (Acer griseum (Franch.) Pax) and trident maple (A. buergerianum Miq.) when compared with other maples. Laboratory results were corroborated during 2001 by a no-choice field assay, in which early instar bagworm larvae performed well on the majority of maples. In contrast, paperbark maple and trident maple were resistant to bagworm feeding, while ‘Autumn Blaze’ Freeman maple (A. x freemanii E. Murray), a hybrid cross obtained by breeding A. rubrum with A. saccharinum, showed moderate resistance.
Leaf Curl and Water Relations of Kousa Dogwoods Showing Resistance to Summer Stress
Authors: Augé Robert M. , Windham Mark T. , Moore Jennifer L. , Witte Will T. , Kubikova Elena , Klingeman William E. , Evans Richard M. , Reiss Jeanese H. , Flanagan Phillip C. , Saxton Arnold M.
Published: August 2020

Kousa dogwood (Cornus kousa Hans.) trees often develop unattractive leaf curling throughout canopies during hot and/or dry weather. Aesthetically superior trees were compared to control trees for their ability to tolerate summer stress, in an established kousa dogwood plantation in 2000 and 2001. An index of leaf curl revealed that superior trees showed less curling than controls during June, July and August of 2000 and 2001. Superior trees often had higher stomatal conductance than trees in both control groups during both years, with seasonal averages 16 to 40% higher in superior than in control trees. Leaf water status, characterized by leaf osmotic potential, remained similar in superior trees and control trees throughout the 2000 summer season. Leaf temperatures were similar between groups during each summer. We confirmed that trees initially selected as having superior visual appearance had measurable differences in foliar characteristics compared to control trees, and that these trees better tolerated summer stress.
Acoustic Detection of Black Vine Weevil, Otiorhynchus sulcatus (Fabricius) (Coleoptera: Curculionidae) Larval Infestations in Nursery Containers
Authors: Mankin R. W. , Fisher J. R.
Published: August 2020

Acoustic detection systems have been developed to locate and target hidden infestations of root weevil larvae in container-grown nursery crops. Tests were conducted in laboratory and field environments with natural and artificial infestations of Otiorhynchus sulcatus (Fabricius) in containers with different nursery plants to determine whether the larvae were large enough for acoustic detection during late fall when scouting for infestation often occurs at commercial nurseries in Oregon. The rootballs of tested plants were examined to verify the presence or absence of larvae. All of the containers rated at high likelihood of infestation contained O. sulcatus larvae (29% of those tested). No larvae were found in any containers rated at low likelihood of infestation (20%). Sporadic sounds were detected but failed to exhibit periodicity suggestive of infestation in 51% of the containers (rated at medium likelihood). Fifty seven percent of these medium-rated containers were infested. Experience with the use of the acoustic system in field environments suggested improvements in user-friendliness and robustness that could improve its utility for early detection and targeting applications in commercial nurseries.
Buffered Phosphorus Fertilizer Improves Growth and Drought Tolerance of Woody Landscape Plants
Authors: Zhang Yuan-Ji , Kuhns Larry , Lynch Jonathan P. , Brown Kathleen M.
Published: August 2020

The effects of alumina-buffered phosphorus (Al-P) were evaluated on growth and drought tolerance of woody plants and on seedling establishment of several tree species grown in containers with soilless media. Al-P reduced phosphorus leaching in all species. Vegetative growth of rhododendron (Rhododendron catawbiense Michx. cv. ‘English Roseum’), forsythia (Forsythia intermedia Zab. cv. ‘Spring Glory’), Ohio buckeye (Aesculus glabra Willd.), and bur oak (Quercus macrocarpa Michx.), measured as plant height, stem caliper, or biomass, was as fast or faster with Al-P as with Osmocote (17–6–10) or monoammonium phosphate fertilizer. Imposition of summer drought during the first growth season slightly reduced growth of rhododendron, with a stronger effect in the second year, while forsythia was more affected in the first season. Rhododendron plants fertilized with Al-P wilted more slowly than controls fertilized with Osmocote. Al-P fertilized forsythia plants grew faster than controls whether drought was imposed or not. Rhododendron plants produced more flower buds in the first year when fertilized with Al-P than with conventional phosphorus fertilizers. At the lower desorbing concentration, drought caused no reduction in percent of plants producing flower buds. A recharging treatment was tested at the beginning of the second season to replace P lost from the Al-P. Recharged Al-P reduced branching and flowering of rhododendron at the end of the second season, possibly as a result of damage from the recharging treatment.
Natural Height Control of Container Grown Eupatorium fistulosum
Authors: Allbritton Gale , Norcini Jeffrey G. , Aldrich James H.
Published: August 2020

Eupatorium fistulosum, Joe-Pye Weed, is a tall [up to 3 m (10 ft)], upright, native perennial that produces large panicles of rosy purple flowers in the summer. However, its height limits its production in containers because tall plants easily blow over and can be difficult to ship. Rooted liners were transplanted into 3.8 liter (#1) containers on two different dates in the spring to shorten the period of vegetative growth before plants initiated flowers in late spring/early summer. Height increase was essentially halted when flowers were initiated, shortly before plants would be shipped. While plants were at least 64% taller than the maximum acceptable height of 61 cm (24 in), it was evident that manipulating the transplant date could be used to reduce the natural height of this species for container production. Moreover, it was shown that a low rate of controlled release fertilizer could be used in production, thereby reducing nutrient runoff. There was no strong evidence that fertilizer rate affected plant height or quality.
Preemergent Bittercress Control in Creeping Phlox (Phlox subulata)
Authors: Briggs Jeanne , Whitwell Ted
Published: August 2020

Preemergent herbicides that effectively control hairy bittercress are not labeled for use on creeping phlox. Studies were conducted to determine preemergent herbicide injury to creeping phlox varieties ‘Crimson Beauty’, ‘Emerald Blue’ and ‘Fort Hill’, and optimal herbicide rates for bittercress control. Barricade (prodiamine) applied at 0.55 kg ai/ha (0.5 lb ai/A) and Surflan (oryzalin) applied at 1.1 kg ai/ha (1.0 lb ai/A) severely injured creeping phlox. Injury was less severe from applications of Dimension (dithiopyr) at 0.83 kg ai/ha (0.75 lb ai/A), Gallery (isoxaben) at 0.55 kg ai/ha (0.5 lb ai/A), Image (imazaquin) at 0.55 kg ai/ha (0.5 lb ai/A), and Treflan (trifluralin) at 2.2 kg ai/ha (2.0 lb ai/A). Minimal to no injury was found with Pennant (metolachlor) at 2.2 kg ai/ha (2.0 lb ai/A) and Snapshot TG (isoxaben + trifluralin) at 2.8 kg ai/ha (2.5 lb ai/A). Two applications of Gallery at 0.28, 0.55 and 1.1 kg ai/ha (0.25, 0.50 and 1.0 lb ai/A), Pennant at 1.2, 2.2 and 4.4 kg ai/ha (1,2 and 4 lb ai/A), RegalKade (prodiamine) at 0.28, 0.55 and 1.1 kg ai/ha (0.25, 0.50 and 1.0 lb ai/A), and Snapshot TG at 1.4, 2.8 and 5.5 kg ai/ha (1.3, 2.5 and 5.0 lb ai/A) did not affect growth of phlox varieties at 27 weeks after treatment (WAT). However, visual injury to varieties ‘Crimson Beauty’ and ‘Fort Hill’ was detected at a greater frequency than injury to ‘Emerald Blue’. Gallery and Snapshot TG applied at 0.28, 0.55 and 1.1 kg ai/ha (0.25, 0.50 and 1.0 lb ai/A) and 1.4, 2.8 and 5.5 kg ai/ha (1.3, 2.5 and 5.0 lb ai/A), respectively, and RegalKade applied at 1.1 kg ai/ha (1 lb ai/A) provided excellent bittercress and yellow woodsorrel control at 8 and 12 WAT. Pennant did not control either weed species at the high rate. In a greenhouse study, Gallery applied at 0.14 kg ai/ha (0.13 lb ai/A) effectively controlled bittercress through 8 WAT, but Snapshot applied at the same rate of isoxaben did not control bittercress. Results indicate that Snapshot TG may be safely applied to creeping phlox at rates of 1.38 to 2.75 kg ai/ha (1.25-2.5 lb ai/A) for preemergent bittercress control. Gallery may also be used safely and effectively at rates of 0.14 to 0.28 kg ai/ha (0.13 to 0.25 lb ai/A).
Effect of Pericarp Removal, Gibberellic Acid Treatment, and Stratification on Seed Germination of Abelia ×grandiflora
Authors: Scheiber S.M. , Robacker Carol D.
Published: August 2020

Seed germination within Abelia R. Br. spp. has been described as slow and inconsistent. An experiment was conducted with seeds of Abelia ×grandiflom (André) Rehd. (glossy abelia) to test procedures to increase germination percentage, uniformity and rate. The effect of pericarp removal was examined on seeds with no additional treatment, and on seeds that were stratified (moist-prechilled) for 60 days at 4C (39F) or immersed in 100 mg/liter gibberellic acid for 24 hr. Treatments were replicated five times with 15 seeds per replication. Seeds were sown on sphagnum peat, and germinated under mist in a greenhouse. Weekly germination counts were recorded for 8 weeks. Seeds with intact pericarps germinated at a significantly higher percentage than those without pericarps. Stratified seeds germinated in fewer days than the other treatments. The combination of stratified seeds with intact pericarps gave the best overall response, with final germination of 62% and a reduction in germination time to 14 days (to reach 90% final germination) as compared to 35 days for untreated seeds.
Identification of Itea virginica Cultivars by Using RAPD-PCR
Authors: Lindstrom Jon T. , Pelto Matthew C.
Published: August 2020

Itea virginica L., Virginia sweetspire, is a flowering shrub native to the eastern United States. It has become popular recently due to its multiple seasons of interest, ease of propagation, and relative lack of significant insect or disease problems. Several cultivars of I. virginica varying in fall color, growth habit, and inflorescence length are now commonly seen in the landscape. These cultivars can be difficult to distinguish morphologically and can be confused in the trade. We used randomly amplified polymorphic DNA (RAPD) markers to reliably identify four of six commonly grown cultivars: ‘Sarah Eve’, ‘Saturnalia’, ‘Henry's Garnet’, and ‘Longspire’. The technique was also useful for identifying unknown or apparently mis-labeled cultivars. However, RAPD markers were not sensitive enough to separate the well-known I. virginica cultivars ‘Sprinch’ (Little Henry™) and ‘Merlot’.
Propagation of Castanopsis sclerophylla by Stem Cuttings
Authors: Conden Peter J. , Blazich Frank A.
Published: August 2020

Two experiments were conducted to develop a protocol for propagation of Castanopsis sclerophylla (Lindley & Paxton) Schottky by stem cuttings. In the first experiment completed in 2000, stem cuttings were taken on three dates representing three growth stages (softwood, semi-hardwood, or hardwood). Semi-hardwood and hardwood cuttings were treated with 0, 2500 (0.25%), 5000 (0.5%), 7500 (0.75%), or 10,000 (1.0%) ppm of the free acid of indolebutyric acid (IBA) dissolved in 50% isopropyl alcohol, whereas softwood cuttings were treated with the same concentrations of the potassium (K) salt of IBA (K-IBA) dissolved in distilled water. Cuttings were placed in a raised greenhouse bench and rooted under intermittent mist. Cuttings taken at the semi-hardwood and hardwood stages began to drop their leaves after approximately 2 weeks and the majority eventually died, with negligible rooting of surviving cuttings. The response of the softwood cuttings to K-IBA was quadratic with the greatest rooting (63%) at 7500 ppm K-IBA. Seventy softwood cuttings that rooted were potted for observance of overwinter survival. Of these, 90% produced a flush of growth during the summer, with 80% overwinter survival. In the second experiment conducted in 2001, semi-hardwood cuttings were taken and treated with 0, 2500 (0.25%), 5000 (0.5%), 7500 (0.75%), or 10,000 (1.0%) ppm K-IBA and placed in a raised greenhouse bench with intermittent mist for rooting as in the first experiment. Results were similar to the semi-hardwood cuttings treated in the first experiment with the free acid of IBA, indicating semi-hardwood cuttings do not root and that the auxin and/or isopropyl alcohol were not toxic to the cuttings.
Tolerance of Native Wildflower Seedlings to Imazapic
Authors: Norcini Jeffrey G , Aldrich James H. , Martin Frank G
Published: August 2020

Plateau (imazapic) at 0.0175 kg ai/ha (0.0156 lb ai/A) to 0.14 kg ai/ha (0.125 lb ai/A) was applied the day after seed of annual phlox (Phlox drummondii), black-eyed susan (Rudbeckia hirta), blanketflower (Gaillardia pulchella), lanceleaf coreopsis (Coreopsis lanceolata), scarlet sage (Salvia coccinea), standing cypress (Ipomopsis rubra), and sundial lupine (Lupinus perennis), were sown on a commercial potting medium or a sandy field soil in plastic pots. All seed were from one commercial source, with additional seed of black-eyed susan, lanceleaf coreopsis, and blanketflower from a second source (Florida ecotype). At 28 days after treatment, slight stand thinning was observed on scarlet sage, blanketflower, and black-eyed susan but the major effect of Plateau was stunting on all species. Annual phlox was the most tolerant of Plateau, with only occasional slight stunting and no stand thinning even at the highest rate. Lanceleaf coreopsis and sundial lupine were slightly less tolerant, with scarlet sage, blanketflower, and black-eyed susan being the most susceptible. Planting medium frequently affected Plateau activity, with stunting usually greater in the commercial medium than in a sandy field soil. For the species in which there were two seed sources, seed source affected tolerance of black-eyed susan and lanceleaf coreopsis. The Florida ecotype of lanceleaf coreopsis was more sensitive to Plateau than the commercial source. For black-eyed susan, sensitivity to Plateau depended on the medium in which seedlings were growing. Results for blanketflower were inconclusive.
Fertilization Methods Affect Growth, Color and Nitrogen Leaching of Winter Annuals in Landscape Beds
Authors: Altland James E. , Gilliam Charles H. , Edwards James H. , Keever Gary J. , Fare Donna C. , Sibley Jeff L.
Published: August 2020

Two experiments were conducted to evaluate fertilizer formulations, methods of application, and frequency of application on growth of winter-grown landscape bedding plants and N leaching. In Expt. 1, ‘Majestic Giants White’ pansy (Viola xwittrockiana Gams.) and ‘Telstar Purple’ dianthus (Dianthus chinensis L.) were planted in raised beds. Four inorganic fertilizer formulations were applied at 4.9 g/m2 N (1 lb N/1000 ft2) either incorporated pre-plant or topdressed post-plant. Additional treatments included an industry practice (IP) of incorporating a granular water soluble (GWS) fertilizer pre-plant and topdressing a controlled release fertilizer (CRF) post-plant, and a pre-plant incorporation of an organically-based fertilizer (OBF) composed of recycled newspaper amended with chicken manure. In Expt. 2, similar treatments were applied to the following species: ‘Bingo Blue with Blotch’ pansy, ‘Telstar Crimson Picotee’ dianthus, and ‘Tall Red’ snapdragon (Antirrhinum majus L.). Across both studies, CRFs generally improved foliar color and plant size compared to GWS fertilizers, while reducing total-N in soil-water in some instances. The IP treatment provided superior foliar color and larger plants compared to other inorganically fertilized plants, while causing no more or less total-N in soil-water leaching below plant roots. Response to the OBF differed among the two experiments. The OBF resulted in adequate foliar color and plant size and reduced total-N recovered from soil-water in Expt. 1. However, it generally provided superior foliar color and size compared to all other treatments in Expt. 2, but also caused elevated levels of total-N in soil-water.
Foliar Application of Auxin for Rooting Stem Cuttings of Selected Ornamental Crops
Authors: Blythe Eugene K. , Sibley Jeff L. , Tilt Ken M. , Ruter John M.
Published: August 2020

Research was conducted to determine whether a foliar spray application of the commercial root-promoting formulation Dip 'N Grow® [10,000 ppm indole-3-butyric acid (IBA) and 5,000 ppm 1-naphthaleneacetic acid] or the potassium (K) salt of IBA (K-IBA) would be as effective as a basal quick-dip for rooting stem cuttings of selected ornamentals. Cuttings of Chrysanthemum pacficum sprayed with Dip 'N Grow® at 50 + 25 ppm IBA + NAA or K-IBA at 0 to 50 ppm showed generally similar root development measures compared to a basal quick-dip; an exception was 10 ppm K-IBA which produced greater total root length. Cuttings of Forsythia x intermedia ‘Lynwood Gold’ typically did not differ in root development under the two application methods, but cuttings sprayed with Dip 'N Grow® at 0 + 0 to 10 + 5 ppm IBA + NAA exhibited greater shoot growth 80 days after sticking (insertion into the rooting substrate) than cuttings receiving a basal quick-dip. Root and shoot development measures were similar or lower for cuttings of Abelia x grandiflora, Hydrangea paniculata, and Lagerstroemia (indica x fauriei) ‘Natchez’ sprayed with auxin compared to a basal quick-dip.
Propagation of Lindera umbellata by Stem Cuttings
Authors: Conden Peter J. , Blazich Frank A.
Published: August 2020

Stem cuttings of Lindera umbellata Thunb. (Chinese spicebush) were taken on three dates representing three growth stages (softwood, semi-hardwood, or hardwood). Semi-hardwood and hardwood cuttings were treated with 0, 2500 (0.25%), 5000 (0.5%), 7500 (0.75%), or 10,000 (1.0%) ppm of the free acid of indolebutyric acid (IBA) dissolved in 50% isopropyl alcohol, whereas softwood cuttings were treated with the same concentrations of the potassium (K) salt of IBA (K-IBA) dissolved in distilled water. All cuttings were placed in a raised greenhouse bench and rooted under intermittent mist. After 12 weeks, the cuttings were harvested and various data recorded. The majority of the hardwood cuttings died, with none of the survivors rooting. Softwood cuttings survived but with overall rooting of only 5%. Response of the semi-hardwood cuttings to IBA was quadratic with the greatest rooting (73%) observed for those cuttings treated with 7500 ppm IBA. However, root number and root length were not significantly affected by IBA treatment. Sixty of the rooted semi-hardwood cuttings were potted and later provided with overwinter protection in an unheated greenhouse but only three of these cuttings were alive by the following summer.
Fertilizer Requirements for Container-grown Buxus spp.
Authors: Musselwhite Sheri , Harris Roger , Wright Robert
Published: August 2020

The objective of this study was to determine the nutritional requirements for container-grown boxwood and to determine if summer dormancy of boxwood can be removed via nutrition. Buxus sempervirens L. ‘Suffruticosa’, B. sempervirens L. ‘Vardar Valley’, and B. sinica var. insularis Nakai ‘Justin Brouwers’ were used for these studies. Various levels of Osmocote 15N–3.9P–9.8K (15N–9P2O5–12K2O) and a 10N–1.7P–4.9K (10–4–6) liquid fertilizer were applied to boxwood in a pine-bark substrate. Maximum shoot dry weight (OSDW) was achieved at 12 to 16 g (.42 to.56 oz) Osmocote per 3 liter (#1) container and 100 to125 ppm N from the liquid fertilizer. Leachate EC corresponding to OSDW ranged from 0.5 to 0.7 dS/m and 0.7 to 1.5 dS/m for Osmocote and the liquid fertilizer, respectively. Leaf tissue N levels corresponding to OSDW weight ranged from 3.1 to 4.3% for Osmocote and 5.0 to 5.5% for the liquid fertilizer. While the fertilizer requirements for boxwood OSDW were determined, additional growth flushes did not occur.
Dose and Concentration Responses of Common Nursery Weeds to Gallery, Surflan and Treflan
Authors: Judge Caren A. , Neal Joseph C. , Weber Jerome B.
Published: August 2020

Preemergence herbicides are applied as often as every eight to ten weeks in container nursery crop production in the southeastern United States. However, weeds often emerge before reapplication. Experiments were conducted to assess the minimum surface-applied doses and the in vitro concentrations of preemergence herbicides required to control susceptible weed species. Greenhouse and outdoor container experiments were conducted to determine surface-applied Treflan (trifluralin) doses required to control large crabgrass and perennial ryegrass. In the greenhouse, 0.8 to 1.1 kg ai/ha (0.7 to 1.0 lb ai/A) was necessary for 6 weeks control. Outdoors, 1.5 to 1.9 kg ai/ha (1.3 to 1.7 lb ai/A) was needed for control 3 weeks after treatment (WAT). However, 6 WAT, 2.6 to 3.4 kg ai/ha (2.3 to 3.0 lb ai/A) was required. Petri dish experiments were conducted to determine the aqueous concentrations of Gallery (isoxaben), Surflan (oryzalin), and Treflan required to control common nursery weeds including eclipta, hairy bittercress, large crabgrass and spotted spurge. The concentration required for 80% shoot inhibition (I80) ranged from 0.4 to 1.5 μg ai/mL for Gallery, 1.2 to 9.8 μg ai/mL for Surflan and 1.1 to 73.8 μg ai/mL for Treflan. The relative response of weeds to aqueous concentrations was consistent with reports from outdoor container efficacy trials.
Strategic Vision of Container Nursery Irrigation in the Next Ten Years
Authors: Beeson R.C. , Arnold M.A. , Bilderback T.E. , Bolusky B. , Chandler S. , Gramling H.M. , Lea-Cox J.D. , Harris J.R. , Klinger P.J. , Mathers H.M. , Ruter J.M. , Yeager T.H.
Published: August 2020

Visions of the future for container nursery irrigation were collected from twelve nursery irrigation scientists, growers and nursery organization leaders. The amount of water available for nursery irrigation unanimously is forecasted to decline over the next decade. Along with declining availability, the cost of water for irrigation is predicted to increase substantially for most nurseries. Limited availability, higher direct cost, and irrigation runoff issues are projected to compel the container nursery industry to adopt procedures and technology that will increase irrigation water use efficiency. Evidence in support of these prognoses, current solutions and suggested options are discussed.
Impact of Application Rate and Interval on the Control of Powdery Mildew and Cercospora Leaf Spot on Bigleaf Hydrangea with Azoxystrobin
Authors: Hagan A. K. , Olive J. W. , Stephenson J. , Rivas-Davila M. E.
Published: August 2020

Efficacy of azoxystrobin (Heritage 50W™) was assessed over a range of application rates and intervals for the control of powdery mildew (Erysiphe polygoni) and Cercospora leaf spot (Cercospora hydrangea) on bigleaf hydrangea (Hydrangea macrophylla) ‘Nikko Blue’. Rooted hydrangea cuttings were transplanted in a pine bark/peat mixture. In 1998 and 1999, azoxystrobin at 0.16 g ai/liter and 0.32 g ai/liter, as well as 0.24 g ai/liter myclobutanil (Eagle 40W™) and 0.84 g ai/liter thiophanate methyl (3336 4.5F™), greatly reduced the incidence of powdery mildew compared with the untreated control where 75% of the leaves of were infected by the causal fungus. When applied at 1-, 2-, and 3-week intervals, both rates of azoxystrobin were equally effective in both years in preventing the development of powdery mildew on bigleaf hydrangea. In 1998, all fungicides except for thiophanate methyl protected bigleaf hydrangea from Cercospora leaf spot. In the last two trials, the incidence of powdery mildew increased significantly as the application rate for azoxystrobin decreased from 0.16 to 0.04 g ai/liter and the application interval was lengthened from 1 to 3 weeks. In general, all rates of azoxystrobin applied on a 3-week schedule failed to provide the level of powdery mildew control needed to produce quality bigleaf hydrangea for the florist and landscape market. When applied at 2-week intervals, myclobutanil was equally or more effective in controlling powdery mildew than any rate of azoxystrobin applied on the same schedule. When compared to the untreated controls, significant reductions in the incidence of powdery mildew on bigleaf hydrangea were obtained with weekly applications of paraffinic oil. No symptoms of phytotoxicity were associated with the use of any of the fungicides screened.
Clonal Propagation of Quercus Spp. Using a Container Layering Technique
Authors: Amissah J. Naalamle , Bassuk Nina L.
Published: August 2020

Clonal propagation of two oak species, Quercus macrocarpa Michx. and Quercus bicolor Willd. was accomplished using a modified container layering technique. The effects of gibberellin (GA4+7) application on stock plant budbreak, as well as the effect of shoot position, stock plant age, and the role of indole butyric acid (IBA) solvents on rooting were investigated. Five hundred parts per million of GA4+7 applied once every fourth day increased budbreak in both Q. macrocarpa and Q. bicolor stock plants. Basal shoots of Q. bicolor from ontogenetically juvenile portions of the stock plant stem rooted 35.7% compared with 1.8% for shoots arising in more distal parts of the stock plant stem. In addition, stock plant age (2-6 years) had no effect on rooting. The effect of the various IBA solvents on rooting in Q. bicolor was 84.3% (98% ethanol), 81.3% (50% acetone), 100% (100% acetone), 28.6% (5% dimethyl sulphoxide-DMSO) and 65% in 10% DMSO respectively; all shoots in this experiment were treated with 10,000 ppm IBA in the respective solvents. IBA dissolved in DMSO treatments resulted in severe apical browning of shoots.
Fertilizer Placement and Herbicide Rate Affect Weed Control and Crop Growth in Containers
Authors: Altland James E. , Fain Glenn B. , Arx Kathy Von
Published: August 2020

Three experiments were conducted in Oregon and Mississippi to evaluate the effect of fertilizer placement and rate of herbicide application on weed control and crop growth. In Expt. 1, Osmocote 18N–2.6P–10.0K (18–6–12) controlled release fertilizer (CRF) was applied at 12 g (0.4 oz) per container (#1) either topdressed, incorporated, or dibbled (placed under the liner prior to potting); and OH2 (pendimethalin + oxyfluorfen) was applied at 0, 28, 56, or 112 kg/ha (0, 25, 50, or 100 lbs/A). Containers were overseeded with common groundsel (Senecio vulgaris). In Expt. 2, Osmocote 17N–3.0P–10.1K (17–7–12) CRF was applied at 18 g (0.6 oz) per container using the same placement methods as Expt. 1; and Rout (oryzalin + oxyfluorfen) was applied at 0, 28, 56, or 112 kg/ha (0, 25, 50, or 100 lbs/A). A hand-weeded check was also included, and containers were overseeded with prostrate spurge (Chamaesyce prostrata). In Expt. 3, containers were fertilized with either 12 g (0.4 oz) of Apex 20N–4.3P–8.4K (20–10–10) CRF or 14 g (0.5 oz) of Apex 17N–2.2P–9.2K (17–5–11) CRF using similar fertilizer placement methods; and Snapshot 2.5TG (isoxaben + trifluralin) was applied at 0, 84, or 168 kg/ha (0, 75, or 150 lb/A). Containers were overseeded with creeping woodsorrel (Oxalis corniculata). Weed control improved with increasing herbicide rate. Across the three experiments, dibbling CRFs with no herbicide resulted in 85 to 97% weed control, while topdressing resulted in 19 to 85% and incorporating resulted in 55 to 88% control. With herbicides, dibbling fertilizer resulted in 89 to 99% weed control while topdressing resulted in 82 to 90% and incorporating 81 to 98%. Dibbling fertilizer resulted in greater shoot growth (growth index) of azalea (Rhododendron ‘Stewartsonian’), holly (Ilex crenata ‘Compacta’), lavender (Lavandula × intermedia ‘Grosso’), and wintercreeper euonymus (Euonymus fortunei ‘Emerald Gaiety’). In Expt. 3, incorporating CRFs resulted in higher root ratings than dibbling in lavender and euonymus. Though measurable differences in root and shoot growth were observed in all experiments, differences were economically unimportant.
Effects of Transplant Season and Container Size on Landscape Establishment of Kalmia latifolia L.
Authors: Hanson Anne-Marie , Roger Harris J. , Wright Robert
Published: August 2020

Mountain laurel (Kalmia latifolia L.) is a common native shrub in the Eastern United States; however, this species can be difficult to establish in landscapes. Two experiments were conducted to test the effects of transplant season and container size on landscape establishment of Kalmia latifolia L. ‘Olympic Wedding’. In experiment one, 7.6 liter (2 gal) and 19 liter (5 gal) container-grown plants were planted into a simulated landscape (Blacksburg, VA, USDA plant hardiness zone 6A) in early fall 2000 and in late spring 2001. Plants in 19 liter (5 gal) containers had the lowest leaf xylem potential (more stressed) near the end of the first post-transplant growing season, and leaf dry weight and area were higher for spring transplants than for fall transplants. For spring transplants, 7.6 liter (2 gal) plants had the highest visual ratings, but 19 liter (5 gal) plants had the highest visual ratings for fall transplants three growing seasons after transplanting. Plants grown in 7.6 liter (2 gal) containers had the highest % canopy volume increase after three post-transplant growing seasons. In the second experiment, 19 liter (5 gal) plants were transplanted into above-ground root observation chambers (rhizotrons) in early fall 2000 and late spring 2001. Roots of fall transplants grew further into the backfill than spring transplants at the end of one post-transplant growing season. Overall, our data suggest that smaller plants will be less stressed the first season after transplanting and will likely stand a better chance for successful establishment in a hot and dry environment. Fall is the preferred time to transplant since capacity for maximum root extension into the backfill will be greater than for spring transplants.
Effects of Soil Compaction and Flooding on the Growth of 12 Willow (Salix L.) Species
Authors: Kuzovkina Yulia A. , Knee Michael , Quigley Martin F.
Published: August 2020

Responses to soil compaction and flooding by 12 Salix species were studied in small mesocosms in a greenhouse over a period of 8 weeks. Two independent experiments were conducted: response of rooted cuttings to soil compaction and response of the same species to three weeks of flooding. Soil atmosphere was analyzed in all treatments. Regardless of level of compaction, oxygen levels were stable and close to atmospheric proportions. However, concentration of carbon dioxide gradually increased in compacted treatments and was the highest in the most compacted soil. Concentration of ethylene remained more or less stable in the compaction treatments. In the flooding treatments a significant decrease of oxygen concentration (9.1%), and significant increases of carbon dioxide (2.15%) and ethylene (1.57μl/liter) took place. All species except S. amygdaloides produced equal or higher biomass in compacted soil compared to a control. Flooding had little effect on the growth of above or below ground parts for most species. Anaerobic conditions triggered a wide range of morphological adaptations: lenticel hypertrophy, formation of adventitious roots (including roots with enhanced aerenchyma), roots growing along the water surface, and roots exhibiting negative gravitropism. Our principal finding was that neither soil compaction nor flooding caused significant reduction in growth of willows.