Dense Internet of Things (DIoT) is fazed by message loss, congestion, and energy consumption, due to a large number of connected devices. One of the main challenges in DIoT environments is to achieve self-adaptable communication without human intervention, where the system is able to dynamically manage its own settings to mitigate common problems. Seeking to promote self-adaptability in DIoT, this paper presents the Autonomic management of GRoup communication for intErnEt of thiNgs applications (AGREEN). It is an autonomous solution for IoT platforms that configures the communication settings to ensure the dynamic control of IoT devices considering a comprehensive set of aspects, such as traffic loss, sensing relevance, amount of energy harvested, and the number of monitoring nodes with renewable and nonrenewable energy. Extensive evaluation results show that AGREEN is able to autonomously change the number of nodes in the monitoring group and to improve system performance in terms of message loss, energy consumption, and communication interval compared to standard protocols designed for IoT.