Can Exterior Plantings count in MRc6?

We have a Science & Math HS Building under construction and have come up short with our rapidly renewable products. We are investigating various approaches in order to meet this credit. Under MRc6 in 'LEED 2009: The Missing Manual' it’s mentioned that “exterior plants purchased for the project probably do count in MRc6 . . .” I found an early LEED Interpretation, #1448 dated 3/6/06, that says exterior plant materials cannot contribute to MRc6 (because using exterior plantings is standard practice and don’t help fulfill the credit intent to reduce use of finite raw materials), but the value of extensive plantings may be deducted from all MR credit calculations. Is the LEED Interpretation, which addressed a question from v2.1, now outdated? Since the LEED 2009 Ref. Guide specifically includes Div. 32 Plantings in the total materials cost, does the comment from The Missing Manual supersede LI #1448? It would much more beneficial to our project to count our exterior plantings in MRc6, but even deleting the value of those plantings would help to a certain extent. I should note that our extensive plantings will integrally link with the school’s curriculum, and include such areas as rain, butterfly, native bird and woodland gardens, as well as habitat and edible landscape areas, and are the focus of an ID credit. Please advise. Thank you.