I know posts on automated plant care are very popular on Gadget Master, so I want to highlight this Arduino appnote - Smart Farm Irrigation System Using Arduino Edge Control.

Researchers from Morocco, the UAE, Egypt, Italy, and South Africa have developed a low-cost IoT- and fuzzy logic–based irrigation system that dynamically adjusts watering using real-time soil and ...

When plants get thirsty, they release a chemical into the soil. That triggers this tech to start releasing water.