The foliage shape and leaf arrangement does look like lilac, though we can't be certain (it's hard to see enough detail, and flowers are key to confirming plant ID), and several species of lilac can be grown in Maryland, though we rarely see them produce seedlings. If you're able to take a close-up photo of the foliage so we can see the serrations you mention, we'll see if any other species come to mind. Otherwise, we might not be able to get more specific until it blooms, though that might require another year or two (at least) of maturing on the plant's part.

Miri