Working the Soil in the Shade Garden
Soil work in the shade garden is different from the meadow. We want to be careful not to injure the trees. Some of my research has suggested avoiding cutting through roots bigger around than a pencil. While I will cut through bigger roots than that, it's necessary to consider the importance of the particular root to the tree. Some trees aren't as well anchored as others. We've all seen trees blown over by storms. Cutting through the tree's anchor support could leave you with a meadow garden rather than a shade garden.
My prefered planting style is to mulch well, wait a year for the mulch to soften the ground and build topsoil. I'll often put down a layer of manure 3 or 4 inches thick over the entire planned garden. I follow this with a layer of woodchips another 3 or 4 inches deep on top of the manure. When I dig this in next year, I've got a nice begining of topsoil which will hold moisture and nutrients for the flowers and shrubs.