Herbaceous perennial ornamental plants can support complex pollinator communities

Human-designed landscapes can host diverse pollinator communities, and the
availability of floral resources is central to supporting insect
biodiversity in highly modified environments. However, some urban
landscapes have relatively few pollinator-attractive plant species and
management in urban environments rarely considers the function of these
plants in generating and supporting a stable ecological community.
Evaluations of 25 cultivars within five commercially popular herbaceous
perennial ornamental plant genera (Agastache, Echinacea, Nepeta,
Rudbeckia, and Salvia) revealed variation in the total and proportional
abundance of visitors attracted. These varieties supported multiple
pollinator functional groups, however bees were the primary visitors to in
this system. Cultivars were assessed according to their function within a
plant-pollinator network. Comparisons of artificial networks created with
the six most attractive and six least attractive cultivars demonstrated
that a planting scheme using the most attractive cultivars would attract
nearly four times as many bee species, including several specialists and
rare species. Plant diversity in the landscape was correlated with
abundance and diversity of pollinator visitors, demonstrating that
community context shapes a plant’s relative attractiveness to pollinators.
We conclude that herbaceous perennial cultivars can support an abundance
and diversity of pollinator visitors, however, planting schemes should
take into consideration the effects of cultivar, landscape plant
diversity, floral phenology, floral area, and contribution to a stable
ecological community.