Floral phenology, floral rewards and insect visitation in an ornamental species Geranium platypetalum Fisch. and C. A. Mey., Geraniaceae

Abstract

This 4-year study examined the flowering pattern, floral display, nectar and pollen production as well as insect visitation to a perennial Geranium platypetalum Fisch. and C. A. Mey. G. platypetalum bloomed from the end of May until the end of June. The pattern of flowering shows the skewed distribution with a tendency towards a more symmetrical curve. The flower display size fluctuated during the flowering season. The most intense blooming fell in the 2 nd and 3 rd flowering week. The flowers exhibit incomplete protandry. Nectar productivity differed significantly between and stage of flower development. Ten and flowers secreted 29.8 mg and 17.6 mg of nectar, on average, respectively, with mean sugar content of 33.9% and 43.1%. The mean total sugar mass in nectar was similar for both stages and the values were 10.2 mg and 8.2 mg, respectively. Pollen mass per 10 flowers was 19.06 mg. Bees (Apoidea) were the principal visitors on Geranium flowers. The peak of daily activity of visitors occurred between 10.00 and 14.00 hrs. The insects gathered mainly nectar. The mean visiting rate was 0.149 visit per flower×min -1. Increased use of G. platypetalum in parks and gardens is recommended in order to enrich the nectar pasture for A. mellifera and wild Apoidea.