The following species are recommended by Dr. Robert Gegear, an assistant professor of biology at University of Massachusetts-Dartmouth. His research includes the conservation of native pollination systems, floral evolution, and bumblebee ecology. Below you will find his recommended plant list for at-risk insects. Visit the Beecology website for more information.
"Things to consider:
If you are planting above 1000 ft. select plants for all three bumblebee species.
If you are planting below 1000 ft. select plants for B. fervidus and B. vagans.
Select nectar and pollen plants so that you have blooms in every season: Early (March-May), Mid (June-July) and Late (Aug-Sept).
Spring floral resources are extremely important for all at risk pollinator types so give them a high priority.
Be aware that in most cases, the species of a plant is far more beneficial to pollinators than named cultivars.
Select plants that target as many species from the three pollinator groups as possible - a good habitat will support species at risk over the entire season."