There was research done, that annoys me I can't find the bookmark. But you can measure communication using fungi as the access point.

It's known that fungi can act as a trading point for plants in that lend some, borrow some when plants are in need. If you hook fungi to a device you can measure communication.

"Trees can communicate with each other through networks in soil. Much like social networks or neural networks, the fungal mycelia of mycorrhizas allow signals to be sent between trees in a forest. These mycorrhizal networks are effectively an information highway, with recent studies demonstrating the exchange of nutritional resources, defence signals and allelochemicals. Sensing and responding to networked signals elicits complex behavioural responses in plants. This ability to communicate ('tree talk') is a foundational process in forest ecosystems."

https://pmc.ncbi.nlm.nih.gov/articles/PMC4497361/

And would highly recommend this book: https://www.merlinsheldrake.com/entangled-life