by a wind physics object, (this may be something I haven't come across - still a newb in many ways) do you mean an empty with a wind added?

this is how I did things and it's worked first time....

Will try and stick a link to the blend file in a few minutes (ftp proggy is playing up:( )

----------

Toolset: Blender, GIMP, Indigo Render, LuxRender, TopMod, Knotplot, Ivy Gen, Plant Studio.