I am listening to a conference right now and a study was quoted that woody plants do not uptake heavy metals.

I did find another study about the uptake of heavy metals in plants. Take a few moments to familiarize yourself with this study because the images are interesting even if you don't want to read a dense peer journal article.

[url=http://www.hindawi.com/journals/ijce/2011/939161/][/url] http://www.hindawi.com/journals/ijce/2011/939161/

From the trenches,
Celeste