Described are a method and a device for efficiently switching multicast data flows from a shared distribution tree to a shortest path distribution tree. The method achieves an efficient and scalable tree switch that reduces the latency of multicast data transmitted from the source to receivers. A determination is made for each source group (S,G) entry in a portion of a forwarding plane database of a router as to whether a byte count for that entry exceeds a threshold value. A message sent from the forwarding plane to the router control plane indicates the (S,G) entries determined to have byte counts exceeding the respective threshold values. For each message entry, the respective shared distribution tree is switched to a shortest path distribution tree. The method achieves a substantial reduction in the number of inter-process messages exchanged between the control plane and the forwarding plane compared to conventional tree switchover techniques.