One of the earliest sources of pollen for honeybees comes from hazel trees. Hazel produces copious quantities of yellow pollen from its male catkins. The powdery shower is a delight to observe, but of course, not so delightful for those suffering from allergies.
The tree has both male and female flowers on each branch. The tiny crimson flowers (no petals, just red styles) burst out of buds and await the wind-carried cloud of pollen to reach them from another tree. Since the tree is wind-pollinated, it does not have to invest in showy flowers like insect pollinated plants do.