Cant find suitable foliage lighting tecniques.

I have areas in my level that need to be dark, such as caves and holes. Lightmass does a very nice job here. The problem is the foliage in the caves and holes: I cant use lightmass on foliage as it would take too much lightmap texture space.
Does anyone have suggestions on how to make the lighting look correct for foliage? i have tried distance field lighting, but it doesnt work well for large spaces such as caves.

Basically, the problem is that indirect lighting cache doesnt work on instanced meshes, and i cant find an alternative method to indirect lighting cache. Is this something that will be adressed in the future?

I have one idea, but dont know how to do it. How can I render out a cube map of static lighting, and have it projected onto surrounding foliage?
Any ideas would be most welcome