Feed the bees by planting early spring/early summer native plants that contain nectar like this beautiful Blue False Indigo. It's critically important to supply NECTAR for adult bees as it is their main food source ---only baby bees eat pollen. Queen bumblebees normally emerge in search of a nest in late March to early April here in Ohio. This plant is sometimes up and trying to bloom and other times it doesn't bloom until late spring/early summer here. Just as the queens have been emerging as early as MID March (2020) some of the plants are too, and some aren't--leaving the food search complicated for the bees.
Should yet the flowers be un-bloomed when Queen bumblebees arrive--don't worry as they will rob the bud of nectar by prying it open! The bees will "do what they gotta do" to get their food as long as you have put a plant there for them! Remember, bloom times for the same native plant that is located in different states might be different.