Evaluation of Native and Nonnative Ornamentals as Pollinator Plants in Florida: I. Floral Abundance and Insect Visitation

Abstract

Diverse floral resources impart immense value for pollinating insects of all types. With increasing popularity and demand for modern ornamental hybrids, cultivation by breeders has led to selection for a suite of traits such as extended bloom periods and novel colors and forms deemed attractive to the human eye. Largely understudied is pollinator preference for these new cultivars, as compared with their native congeners. To address this gap in understanding, 10 species of popular herbaceous flowering plants, commonly labeled as pollinator-friendly, were evaluated at two sites in Florida [U.S. Department of Agriculture (USDA) cold hardiness zones 8b and 9a] and across three seasons for their floral abundance and overall attractiveness to different groups of pollinating insects. Each genus, apart from pentas, encompassed a native and nonnative species. Native species included blanket flower (Gaillardia pulchella), lanceleaf coreopsis (Coreopsis lanceolata), pineland lantana (Lantana depressa), and scarlet sage (Salvia coccinea). Nonnative species included Barbican™ yellow-red ring blanket flower (G. aristata ‘Gaiz005’), Bloomify™ rose lantana (L. camara ‘UF-1011-2’), mysty salvia (S. longispicata ×farinacea ‘Balsalmysty’), Lucky Star® dark red pentas (Pentas lanceolata ‘PAS1231189’), ruby glow pentas (P. lanceolata ‘Ruby glow’) and Uptick™ Gold & Bronze coreopsis (Coreopsis × ‘Baluptgonz’). Flower-visiting insects were recorded during five-minute intervals in the morning and categorized into the following morpho-groups: honey bees, large-bodied bees (bumble and carpenter bees), other bees (small to medium-bodied native bees), butterflies/moths, and wasps. Floral abundance and pollinator visitation varied widely by season, location, and species. Of the plant species evaluated, nonnative plants produced nearly twice as many flowers as native plants. About 22,000 floral visitations were observed. The majority of visits were by native, small to medium-bodied bees (55.28%), followed by butterflies and moths (15.4%), large-bodied native bees (11.8%), wasps (10.0%), and honey bees (7.6%). Among plant genera, both native and nonnative coreopsis and blanket flower were most attractive to native, small to medium-bodied bees (e.g., sweat bees, leafcutter bees) with the greatest number of visitations occurring during the early and midmonths of the study (May–August). Across the study, butterflies and moths visited lantana more frequently than all other ornamentals evaluated, whereas pentas were most attractive to wasps. Large-bodied bees visited plants most frequently in May and June, primarily foraging from both native and nonnative salvia. While results from this study showed nominal differences between native and nonnative species in their ability to attract the studied pollinator groups, care should be taken to making similar assessments of other modern plant types.

High variability in the attractiveness of municipally-planted decorative plants to pollinators

“…In each location, a patch of each plant type available was examined. To do this we carried out a standardised observation following Kalaman et al (2022) in which a 40 x 60cm quadrat was placed on the planted area, and all insects in the area or entering the area over 1 minute were recorded. We hoped that such an extended observation period, rather than the “snapshot” method deployed in other studies (Garbuzov et al 2015; Palmersheim et al 2022), would allow us to search more closely for smaller or more inconspicuous insects, such as ants or small bees.…”

“…However, the reverse situation also exists – for example, Anthemis tinctoria was reported to attract a wide variety of pollinators such as wild bees, flies, and butterflies, but not honey bees or bumble bees (Rollings and Goulson 2019). While various floral traits have been found to correlate with attractiveness to pollinators (such as floral area cover (Grindeland et al 2005; Marquardt et al 2021a; Kalaman et al 2022), colour (Reverté et al 2016; Chapman et al 2023), shape (Howard et al 2019; Erickson et al 2022; Chapman et al 2023), and nutritional offering (Comba et al 1999; Corbet et al 2001; Chapman et al 2023)), the huge variety of cultivars and interaction with local conditions make accurate prediction of cultivar attractiveness difficult. As such, Rollings and Goulson (2019) recommend that tests for the attractiveness of a wide variety of ornamental cultivars be carried out, ideally at various sites with varying environmental conditions.…”

Ornamental Invasive Plants in Florida with Research-founded Alternatives

“…Florida boasts abundant flora with more than 3300 native plant species, yet less than a quarter of these are in cultivation. When incorporated into appropriate spaces, native plants can offer desired aesthetic attributes such as color and form, while contributing biodiversity and function for ecologically friendly landscaping (Kalaman et al 2022a(Kalaman et al , 2022b). In the past 2 decades, significant progress has been made in the propagation, production, and landscape trialing of more than 15 native species that are either 1) attractive in their natural areas and have potential for the ornamental industry (Campbell et al 2021(Campbell et al , 2022; or 2) are already in limited cultivation, but merit widened use for landscapes and gardens (Smith et al 2022;Young et al 2022).…”