ASHS 2024 Conference

Florida is home to over 300 species of native wild bees, some in critical decline. To encourage gardeners to plant bee friendly species that support bee pollinators year-round, an online application called BeeGardens was built using a shared library of code and a relational database management system. The application, accessible by a mobile device or computer, enables users to quickly access over 85 bee-friendly plants that attract 12 primary bee groups; and provides tips for incorporating these into different landscape designs (https://ffl.ifas.ufl.edu/bees). The functionality and usefulness of the app was evaluated by students enrolled in two courses at the University of Florida: Florida Native Landscaping and Annual and Perennial Gardening, taught in different semesters. Before and after the semester, students were asked to report their abilities to 1) identify bee-friendly plants, 2) identify bee pollinators, and 3) design a bee-friendly garden, using a Likert scale with responses ranging from 1 (strongly disagree) to 5 (strongly agree). Means of pre- and post-test responses showed a significant perceived knowledge gain upon using the BeeGardens online application in both courses. This data was consistent with pre- and post-tested means where students were asked to identify three major pollinator plants and three major pollinators using multiple choice response options. Test scores increased by 26.3% and 37.9% in Annual and Perennial Gardening and Florida Native Landscaping, respectively. The majority of students (95.0%) agreed or strongly agreed this learning tool was organized, easy to navigate, and would use it in the future. Since its inception in March 2021, this web application has been accessed by over 26,554 new users from across Florida and beyond.

Declines in pollinator populations have gained much attention over the last decade. Exposures to pesticides are one potential contributor to these declines. Given that the ornamental plant production industry produces crops that are attractive to pollinators and that pesticide use is often integral to ensuring plants are pest-free, attention is needed to assess and possibly reduce contamination of flower nectar and pollen before plants go to market. Three major factors associated with pesticide management practices that may influence contamination of floral resources are: application method, application rate, and application timing relative to flowering. Using the systemic insecticide thiamethoxam as a model pesticide and Salvia x ‘Indigo Spires’ (Salvia longispicata x S. farinacea) as a model species, this study investigated the influence of each of these factors on contamination of nectar. Plants were treated by spray and drench methods, at low and high rates according to the pesticide label, and before flower buds formed or close to the time of floret opening. Nectar samples were collected using microcapillary tubes when all plants were uniformly flowering and thiamethoxam concentrations were analyzed by LC-MS/MS. Concentrations of thiamethoxam in nectar were highest in drench applications, regardless of application timing and rate, and exceeded published LC50s for native bees and/or honeybees. Thiamethoxam concentrations were much lower in the spray-applied treatments, but they still exceeded published LC50s for native bees and/or honeybees except for the spray treatment applied before blooming at the low rate. These results provide insight into how some pesticide management practices influence contamination of floral resources and indicate a need for developing best management practices focused on limiting thiamethoxam exposures once plants go to market. Additional studies are underway to evaluate other plant species and systemic insecticides to address gaps in knowledge.

Pollinators play a crucial role in the ecosystem, human health, and the economy. However, despite the significance of pollinators, their populations are declining globally. Pycnanthemum is a marketable pollinator-attractive plant that could supplement pollinator resources in the landscape. Breeders would benefit from a comparison of the pollinator attractiveness between Pycnanthemum species and accessions. Cultivating Pycnanthemum should focus on aesthetic traits and maximizing pollinator abundance and species richness. Pollinator visitation was compared among three species and five accessions of Pycnanthemum (P. flexuosum (F), P. virginianum (V), and three accessions of P. tenuifolium (T1-T3)) using observations and capture. Lepidoptera, honey bees (Apis mellifera), Diptera, carpenter bees (Xylocopa spp.), small bees, and bumble bees (Bombus spp.) were observed most abundantly on Plant F. Plant V attracted the highest number of pollinators overall, with Apis mellifera (honey bees) accounting for more than half of the pollinator visitation. Xylocopa spp. (carpenter bees) and honey bees did not have a significant preference between the species. Plants F, T2, T3, and V attracted the greatest abundance of Diptera (flies). Wasps were most attracted to Plants T3 and V, while Bombus spp. (bumble bees) was observed most often on Plants F and V. Plant F attracted the highest number of Lepidoptera (butterflies and moths) and small bees. The species richness of pollinators did not significantly differ across Pycnanthemum species, with at least 24 to 29 different pollinator species visiting each plant. A range of factors, including olfactory cues, the morphology of plants, and accessibility of resources, may have affected pollinator preferences. Determining which Pycnanthemum species attracted an abundance and diversity of pollinators provides breeders a foundation for cultivation and conservation expectations.

Crape myrtle (Lagerstroemia L.) stands as a ubiquitous presence in landscapes worldwide. Beyond its captivating smooth and exfoliating bark, a spectrum of flower colors, and impressive variable mature heights, the artistic modeling potential of crape myrtle has found favor in the high-end landscape market. Crafting a crape myrtle tree becomes a gratifying and imaginative endeavor. The preeminent modeled shapes include vases, screenings, letters, columnar forms, dragon-inspired (animalistic), symbolic representations, pavilions, tunnels, tree bonsai, ornamental root architecture, and even cartoon characters. Constructing a foundational armature from steel demands your artistic prowess and creativity, serving as the structural basis for the tree. Opting for fast-growing crape myrtle cultivars with pliable branches becomes imperative for success. Consistent pruning becomes a requisite to mold the growth pattern according to our artistic aspirations. Utilizing modeling wire facilitates the creation of the trunk and branch framework, with strategically tied crossed knots enhancing natural grafting unions. Developing distinctive Lagerstroemia plants requires a more extended timeframe and demands advanced modeling and pruning techniques compared to conventional growth processes. This production journey provides ample creative freedom and the ultimate performance should align with our artistic vision and the preferences of our clientele. Future studies should delve into plant growth dynamics and the development of trunk/branch anatomical structures to further enhance our understanding of this artistic horticultural practice.

Hedge shaping and size maintenance is often accomplished with electric or gas-powered shears due to a lower cost compared to hand pruning. Shearing plants arbitrarily removes the apical growing points from external portions of the shrub to achieve a desired shape and size of the plant and often results in poor quality cuts, leaving ragged ends of woody tissues or leaves. Contrarily, hand pruning makes strategic, ‘clean’ cuts often back to lateral branches to achieve these goals. Use of plant growth regulators like paclobutrazol (PBZ) can reduce the frequency of pruning and could be a useful component of a hedge management program. The purpose of this study was to investigate the effects of shearing, hand pruning, and/or PBZ application on regrowth of foliage and non-structural carbohydrates (NSCs) of ‘Winter Gem’ boxwood over time. Fifteen shrubs each per pruning type x frequency combination were pruned with bypass hand pruners (hand pruned) or gas-powered shears (sheared) in 2021, 2022, and 2023 once or twice per growing season. In addition, another 15 shrubs each were sheared once followed by an immediate application of a foliar PBZ (i.e. Trimtect®) in accordance with the label using an electric backpack or left as non-pruned controls. In 2021 and 2022, shrubs were pruned by removing 15 percent of the overall height and 20% of the overall widths in two perpendicular directions of each shrub. In 2023, pruned shrubs were cut back to the previous season’s overall height and width. Regrowth was measured by weighing the fresh biomass removed at each pruning and NSCs were measured from ten woody twigs from the exterior of each shrub using the phenol-sulfuric acid quantification method. Two and three years after pruning, shearing shrubs twice had significantly more biomass produced year over year compared to hand pruning, while PBZ treated shrubs had the least amount of regrowth. NSCs trended to be highest in shrubs that were hand pruned once or in PBZ treated shrubs, while the least in shrubs that were sheared twice. PBZ-treated shrubs had tighter clusters of internodes resulting in approximately 30% reduction in stem elongation compared to controls. The differences in growth dynamics and carbon storage across these different pruning strategies can have different long- and short-term implications in managing boxwood hedges, which will be presented here.

Root defects, especially circling roots, are a major concern when planting container-grown trees. In this study, we compared survival, crown dieback, and plant water potential of four common landscape tree species (Carpinus caroliniana, Liriodendron tulipifera, Ostrya virginiana, and Platanus × acerifolia) in response to root modifications (control, bare-root washing, shaving, and vertical slicing) prior to planting. P. × acerifolia trees were robust with respect to root correction treatments and had 100% survival except for some mortality following vertical root-ball slicing. In contrast, C. caroliniana, L. tulipifera, and O. virginiana trees had significant mortality and crown dieback in response to bare-root washing. The responses of these species to bare-root washing reflected extreme plant moisture stress immediately after planting. These three species are also considered ‘difficult to transplant’ as bare-root nursery stock. Our results suggest that trees that are generally known to be difficult to transplant as bare-root stock are poor candidates for extreme root disturbance such as bare-rooting when grown as container trees. In contrast, shaving and vertical slicing had little or no adverse effects on tree survival, crown dieback, or plant water potential.

Mulching is a common task in the landscape industry, with materials selected to provide environmental benefits (i.e. moderating soil conditions, limiting weed growth) and aesthetic value, with colored mulches often employed to add an artistic element to landscapes. Questions arise over possible effects that mulch color may have on soil temperatures, especially when using darker materials. This research investigated the effects of a commercially available shredded mulch (dyed black, brown, or red) on soil temperature and light transmission in model research plots. A plot at the Hammond Research Station was cleared, graded, and prepared with a typical bed mix comprised of pine bark and sand. A total of 21 sub-plots were prepared, where each sub-plot had a remote temperature sensor buried at the base of the bed mix (8 cm below surface), and a temperature and light sensor placed over top of the bed mix. Mulch was applied to depths of 5 cm or 10 cm directly over the top of the temperature and light sensors, with n=3 for our control (no mulch over the bed mix), red mulch (n=3 for depth of 5 cm and n=3 for depth of 10 cm), brown mulch (n=3 for depth of 5 cm and n=3 for depth of 10 cm), and black mulch (n=3 for depth of 5 cm and n=3 for depth of 10 cm). Soil temperature conditions (both within the mulch itself, and at the base of the bed mix) as well as light transmission through the mulch layer was recorded every 30 minutes throughout a spring and summer season at the Hammond Research Station. Blank (unmulched) plots naturally experienced the most light transmission and temperature extremes. Regardless of mulch color or depth, light transmission was substantially reduced (and often eliminated) equivalently between mulch treatments. Temperature was measured both within the surface mulch layer, and 8 cm below into the subsurface bedding mix. While subsurface temperatures were effectively equivalent between all mulched plots, surface temperatures exhibited substantial differences between mulch colors and depths. Thinner mulch layers experienced more extreme surface temperature fluctuations, with mulch color influencing peak temperatures. The results of this work suggest that different mulch colors and depths have a greater influence on temperature at the immediate surface, but far more muted differences in subsurface temperatures.

Formosan Sub-terranean Termite Landscape Mulch Consumption Payton Floyed1, Edward Bush*2, and Qian Sun1 (1)LSU Department of Entomology and (2)LSU AgCenter, SPESS, Baton Rouge, LA Many landscapers utilize organic mulch substrates composed primarily of wood and bark, making it an ideal food source for the Formosan subterranean termite (Coptotermes formosanus). Formosan termites are one of the most destructive structural pests and recognized as one of the 100 worst invasive species in the world. While foraging, these termites can find and may be able to fully establish colonies in landscaping that uses mulch. The mulch type that attracts the most termites has not been widely investigated and continues to be an issue that needs to be determined. The objective of this research was to measure the biomass consumption by termites. Three C. formosanus colonies were used, two from New Orleans, Louisiana, and one from Gonzales, Louisiana. All were maintained in the laboratory using three total replications per experiment over a 14 d period. Five-hundred total termites (450 workers and 50 soldiers) were placed in each arena (7.5”x10”x4” plastic bin) which used a sand layered bottom for both worker and soldier termites. Each arena was covered with a dark plastic bag to mimic typical subterranean foraging conditions. Mulch particle size distribution and bulk density resulted in expected differences with crushed pine straw having the finest particle size (>50% particle size