How to select UV map for hair materials with textures in cycles

I have added particle hair to a mesh, and now I an working on the hair material. I understand that it is possible to use textures in that material definition, and that the texture coordinates somehow come from the mesh. For each hair the texture coordinate of the hair’s ‘root’ (the point where it is connected to the mesh).

Now my problem is, how to select one of the UV maps (defined on the mesh) to use for this purpose. My attempts to far have failed. When I leave the vector input of the texture node unconnected, somehow the texture is mapped on the mesh anyway (don’t know how it is don’t, some kind of automatic thing, I guess, but it is not using any of the UV maps I have created), but when I try to explicitly specify which UV map to use, the hair will just get all the same color. For testing I mapped the material on the mesh itself and it worked fine, but it simply won’t when using it for the hair.

Does someone have an idea what I am doing wrong?