Trees created in the tree creator work just fine in the wind(windzones). But when I try to use one of the unity terrain asset trees it doesn't seem to be affected by a windzone. Neither does the grass. Also bushes seem to be broken in the terrain editor. (These are also from the Terrain Assets Package) I set them to vertex lit like I believe I should set them to, but the textures on the leaves mess up showing planes not just the details I want. I know this is a shader issue, but i have no idea what shader I should set them to. Right now I have the bushes rendering mode set to Grass, and this fixes the leaves issue, but if I look at the root of the bush, it physically moves, it doesn't sway (and doesn't seem to be affected by windzones either.) I hope if these are legitimately broken things, that Unity 4 fixes them.
trees: manually modeled trees using the soft occlusion shaders will never bend in the wind (windzone) if placed manually and not within the terrain engine - whereas trees modeled with the tree creator will. this is due to the soft occlusion shaders which expect wind passed to it in a 4x4 matrix (done by the terrain engine) – which i don’t know how to setup…
grass: as far as grass is concerned: it is not affected by windzones but only by the wind parameters within the terrain inspector.
bushes: the standard vertex lit shader is made for solid objects like little rocks. so you are doing right to use the "grass shader". but you can find some advanced shaders on the asset store (free): just look for the "advanced terrain shaders" or "ats". or follow this link: http://forum.unity3d.com/threads/119127-Coming-soon-Advanced-terrain-shaders-%96-Volume-2