Nectar and pollen in Acer trees can contribute to improvement of food resources for pollinators.

In the present study, we quantified floral resources (nectar and pollen production) and their quality (nectar sugar composition, pollen protein content, pollen amino acid composition) in five Acer species (f. Sapindaceae) growing in forests and commonly planted in urban areas in the temperate zone. Acer trees provide high amounts of sugars and/or pollen. No nectar was produced by A. negundo flowers. The other species produced nectar in functionally female flowers. The floral nectar was composed of sucrose, glucose, and fructose and was classified as hexose-rich or sucrose-rich. The pollen of all the Acer species contained essential amino acids. Acer trees should be planted for improvement of cost-effective food resources in various landscape types (agroforestry, urban areas), with the exception of A. negundo (an invasive species with no nectar available). However, maple trees alone are not sufficient to support pollinators, and other plant species flowering before and after Acer spp. should be planted to ensure a continued supply of food for pollinators.