Charlie Pridham wrote:
Yes they are shallow rooted. I can not remember now why you went off the
idea!

Charlie, thanks for the confirmation. I'm getting excited. A mass of
rhododendrons below this house would be PERFECT. It was our original
thought before buying, but then, once we'd moved in, we discovered the
septic tank soakaway was laid right through our front lawn and
subconsciously we accepted that rhododendron "trees" would have root
systems that equated to their thick strong trunks.

Now, you can see above, that someone else has reminded me of the
unlikelihood of rhodies with 5"-diameter trunks not having root systems
that penetrate only within the top six inches or so. So I guess it
comes down to people's definitions of "shallow-rooted". For our
purposes, because of the soakaway, I think I now need to do some serious
googling to find out if the "shallow roots" of a mature rhododendron
penetrate near or beyond the 1-foot level.

Eddy.