I think I saw them grafting another Northern Highbush onto Spartan root stock.I'm not sure or haven't heard of crossing two different kinds like that.It'd be interesting. Brady

Knew a guy in FL several years back who was attempting to graft good fruiting blueberry varieties onto established native farkleberry/sparkleberry (V.arboreum) plants on his place. Have never seen a progress report from him, though.