what is a stone planter bed? you mean a planter with perreinals in it?
re drainage, this soinds like a big problems. With an impenitrible slab two inches down, everything is either rather wet or rather dry eh? maybe put a nice gravel on it? - A

Sorry. Good questions--I wasn't clear enough. The area backs up on an old free standing garage and the slab was originally poured as an extension of the garage floor. I want to build a garden against the side of the garage. I think the only option is to build a raised bed. I would like to do that with dry stacked fieldstone using a moisture barrier against the garage side to prevent rot. I had assumed that I would have to have at least 4" of gravel in the bottom to allow for drainage--are there other issues I should consider to make this work?

You may be assuming that your drainage needs to be perpendicular (straight down) but this is not right. If the base of your raised bed the concrete) has a fall outwards toward the dry stone then this will drain and if the whole planting medium is sharp and not just the bottom few inches you should have no problem.

it seems to me that shrubs will be a bit contsrained... i.e. they willnever get very deep roots... but then you are an expert with shrubs and all, so i supoose that thisisn'texactly your question...
there are some studies about the amount of root space that trees in cotainers need(as in a city installation) . i'm not sure about shrubs... but no doubt size is relative to root. The value of many shrubs is in thier flowers... perhaps this is impacted...
- A

Thank you for the compliment--however I am not an expert by any means. The garden bed will be largely perennial and sub-shrubs with the bones coming from deer resistant evergreen plants like hellebores and small boxwoods. The garage wall is very picturesque with clapboard siding and a window. I haven't done the drawings yet, just exploring possibilities...I would imagine that root issues would be relative to type of roots--a plant with a tap root would never work in this situation, but shallow rooted plants would. Just more food for thought...

well shrus need more root space than most perrenials... sub shrubs can be all over the place. Trees need at least a 4 ft4 ft space say only two feet dep and they can get pretty darn big... being inoug for a city sidewalk. I don't think I'd do anything with less that a foot of soil. and for sub shrubs like hebe probably more like two feet.
One issue, since it is essentially a box, perhaps it is wise to include an undermulch drip irrigation to keep this root packed box constantly at proper moisture levels.
- A