Thanks everyone for your suggestions. Sounds like Clematis is it! I
haven't thoroughly checked the area yet but I think there's a decent
amount of soil there. Just to verify this with those of you who've
grown clematis before...is it pretty easy to keep in check? How often
(if at all) do you think I'd have to trim it to prevent invasion into
the shrub? Or does clematis usually prefer to climb upwards rather than
out? Thanks for your help!