Urban Bees Benefit from a Native Forest Species Grown in a City Environment-A Case Study of Geranium Phaeum L.

Abstract

This two-year study tested whether urban bees benefit from the forest perennial Geranium phaeum L. replanted from natural stands to an urban environment. The flowering abundance and phenology, spectrum of insect visitors, nectar and pollen production, and the energetic value of nectar were investigated in Lublin, SE Poland. The apiarian value of G. phaeum was studied for the first time. The species bloomed abundantly from late April to early June and can be regarded as a valuable spring food resource for urban bees, mainly bumblebees, which accounted for >50% of all visits in both years of study. Bees collected mainly nectar. The highest daily pollen and nectar sugar amount offered by a plant reached 73.7 mg and 36.5 mg, respectively, with the caloric value of nectar of 146 cal. The estimated mean sugar yield, caloric value of nectar and pollen yield · m-2 were 1.7 mg, 6.9 kcal, and 3.4 mg, respectively. The current study confirms the advantage of using native plants in urban landscaping and proves their positive role in strengthening both wild and managed bee populations in cities. The finding that wild plants translocated from the natural habitat can develop a self-sustaining population in the urban environment and establish beneficial relationships with urban bees is of interest in terms of the conservation of both native plants and pollinators.