I’ve heard that in northern climates, apple trees are one of the best providers of early-season bee food. Dandelions are another, and I’ve been actively dead-heading (plucking the flowers that have finished blooming and are about to produce seeds) the clumps in my yard to not only keep them from propagating out of control, but to also promote more flowers during the hunger gap. It’s a nice meditative activity to saunter around the yard for a few minutes daily picking spent flower heads.