Date of Completion
Dr. Jessica Lubell, Dr. Mark Brand, Dr. Karl Guillard
Field of Study
Master of Science
There is increased interest in native plants for landscaping to support pollinators. The majority of native plants sold by nurseries are cultivars. Some consumer and conservation groups question the suitability of native cultivars to support pollinators. This work evaluated insect pollinator visitation for six native shrub species, and one or more cultivars of each species. The following species were installed in a full sun field behind the University of Connecticut Floriculture Greenhouse Facility in a randomized complete block design with three replicates: Aronia melanocarpa, A. melanocarpa ‘UCONNAM012’ Ground Hog®, A. melanocarpa ‘UCONNAM165’ Low Scape Mound®, Clethra alnifolia, C. alnifolia ‘Hummingbird’, C. alnifolia ‘Ruby Spice’, Dasiphora fruticosa, D. fruticosa ‘Goldfinger’, D. fruticosa ‘Pink Beauty’, Hydrangea arborescens, H. arborescens ‘Annabelle’, Kalmia latifolia K. latifolia ‘Sarah’, Physocarpus opulifolius, and P. opulifolius ‘Monlo’ Diabolo®. For each plant in 2017 and 2018 insect visitation was measured on ten different occasions during the bloom period using visual observation with each observation period lasting 5 minutes. Insects were identified to the following 12 categories: Apis mellifera, Bombus spp., Andrenidae, Halictidae, Megachilidae, other bees, Lepidoptera, Syrphidae, other flies, wasps, Coleoptera, and other insects. Data was collected on plant and inflorescence size. Insect visitation was similar for C. alnifolia and its cultivars and K. latifolia and its cultivar. A. melanocarpa had more Andrenid visitors than both of its cultivars, which was not unexpected since A. melanocarpa was significantly taller than the cultivars and produced more inflorescences. Floral densities were the same on A. melanocarpa and its cultivars, so the cultivars are not less attractive to pollinators, but their smaller size limits the number of visitors. D. fruticosa had more visitors of Bombus spp. and Megachilidae than both of its cultivars. These insects may have been less attracted to ‘Pink Beauty’ due to its pink flower color and ‘Goldfinger’ due to its wider flowers, which result from it being a tetraploid. H. arborescens ‘Annabelle’ had fewer visitors of Bombus spp. and Halictidae than H. arborescens, because ‘Annabelle’ flowers consist of 58% sterile florets, compared to the 1% sterile florets for the straight species. Syrphids preferred P. opulifolius ‘Monlo’ to P.opulifolius, possibly because white flowers contrasted more strongly with the reddish purple foliage of ‘Monlo’ compared to the green foliage of the straight species. These findings indicate that cultivars are not universally less or more attractive to pollinators and must be evaluated on a case-by-case basis.
Ricker, Jacob Gordon, "Suitability of Cultivated Forms of Native Shrubs to Support Pollinators" (2019). Master's Theses. 1323.
Dr. Jessica Lubell