First, do your tests!
Second, keep in mind that although foliage is green, it reflects other colors as well (e.g. IR) and that foliage from different plants have different spectral responses.
That said, I've had good luck with a Wratten #44 filter, and a regular 80B color correcting filter for lightening foliage (The Wratten #44 filter approximates orthochromatic film). Both these filters will raise shadow values considerably.
The number 11 yellow/green filter is less effective; a 58 filter may work better, but I haven't tried it for a long time.