This, from the last site you list, is impressive:
http://www.all-model-railroading.co.uk/amr/chapter06.htm
I thought you'd like that, Tom. You can also use plastic fern from craft stores like Michaels or Hobby Lobby in place of the real fern. I think it may hold up better over time. I've got a few more links to dig up, I'll post them in the next couble of days.
EDIT: I see Paul is using plastic fern in that tutorial. I've seen Paul (or someone) use real fern in the past.Steve Pettit's work is really good too. His NMRA page has a few nice structures on it.
http://www.nmra.org.au/Layout_Tours/Pettit/index.html