An ever increasing variety of applications are being addressed by wireless sensor networks, resulting in a continuous proliferation of their deployments, which are in many cases co-located. This development is mostly hindered by the operational complexity involved with management and maintenance of large numbers of small, battery powered wireless sensor devices. The paradigm of energy aware self-growing networks addresses these difficulties. It focuses on power saving which reduces the major maintenance complexity of replacing batteries, and on automatic cooperation between networks which reduces the management complexity. However, cross-network cooperation requires cross-network communication, which is not straightforward as they typically operate on different frequencies. Receiver Directed Transmission is a MAC layer protocol which can bridge this gap, while also minimizing interference and thus reducing the number of transmissions. In this work we study how Receiver Directed Transmission can be combined with Low Power Listening in order to take advantage of the reduced number of transmissions to improve power consumption. We then implement the selected approach on TinyOS and verify its operation experimentally.