I have a large Maple that is critical to shading the deck. The ground below is quite filled with roots that hog all the regular watering. The area gets part sun (west) in the afternoon. Grass under the tree (about 500 sq ft) not an option because the soil pH is high and the amendments we add (drills) destroy the grass. I do have a 6" trench dug around the outer perimeter (per Janet M's suggestion) that will hopefully prevent ground cover from growing into the outlying lawn. We do have bold deer. Vinca minor failed horribly. Contemplating Ajuga Chocolate Chip. Wondering if anyone has suggestions, experience with the ajuga, etc. Thanks for any suggestions!