The crocus bulbs we plant in the autumn flower in February and early March. We love them because they bring early colour to the garden after winter. But the bumblebees love them for food. I always buy a variety with a bee-friendly label on it just in case such as Crocus tommasinianus (Best to be on the safe side these days with so many sterile plants sold just for their looks rather their ability to feed bees).
When bumblebee queens emerge after hibernating they’re often starving, so they need all the food they can find. But they only eat nectar and pollen from flowers. Nectar gives them the energy to forage for more food and to look for a good place to make a nest. Pollen is the protein-rich food they feed to their babies, after their eggs have hatched into hungry larvae.
Crocuses are among the best early flowering food for bees if they’re planted in the sun where the bees like to forage. I also plant mine under our apple tree with snow drops, because they’re natural woodland flowers and look so lovely there, but in truth it’s a bit too shady for the bees.