I have a good amount of finely ground leaves from fall and they haven’t broken down much. Can they be tilled into the garden this spring?
I would wait. For now, use a good compost, rotted manure, coir, etc. Light amendments in the spring and heavier in the fall. BUT, I would use the leaves as a topdressing / mulch after you get the garden planted. Those and grass clippings (not sprayed with herbicides) are great for mulching the garden. This fall, then you can till them into the garden. Keep doing that, and you’ll eventually have some pretty nice soil in the garden!