Does anyone know if you can put real pine needles/twigs on a cake covered in buttercream?...I am making a Christmas cake for a client and I would like to put on real pine instead of fondant or icing..will it be okay?...

Why not, it's all natural! 

AIts a bit risky for me. Putting anything from the outdoors that has been exposed to dust, wind, rain, etc on a cake would be a no for me.

i did a brief online search and learned that pine needles are edible--they even brew a tea with them--

i'd rinse them off first of course  -- but honestly it sounds better to use it on a plate of food because they routinely get green garnishes ex. parsley -- does not appeal to me on a cake -- not to mention piping pine needles is fun ;)

but i'm sure you will make it pretty --