Some of the Exbury Azaleas are more upright and not so spreading, but sounds like it may be too dry for them. I'm thinking Sambucus may need more sun to keep the deep foliage color, might get enough though. Oh yes, do start a thread for other plants for the area- tree roots and dry shade a such a bitch to deal with! The main entry to our house is riddled with roots from a huge Silver Maple, and of course it's the area that needs ornamentals the most. I've tried lots, and finally am having some success getting some things established there, but it has been tough.
