Hmm let's see. Besides the obvious cherry blossom mania in DC (the park rangers who work the National Mall call it March Madness)... there was an apple blossom festival in Winchester VA this past weekend. There's a strawberry festival in St Mary's County, MD in two weeks. There's plenty of agriculture in Virginia and Maryland so I expect there are various other festivals that I haven't heard of. Probably a crab festival in Maryland, too.

We have pawpaws here, though I only know about them from reading info from a local wildlife sanctuary.