I've been looking into this myself a bit, and it's worth mentioning that the ESP32 can do 8 channels worth of analog input (and that's only on the first ADC, th

I've been looking into this myself a bit, and it's worth mentioning that the ESP32 can do 8 channels worth of analog input (and that's only on the first ADC, there's a second you can use if you disable WiFi, and that's something you'll likely be doing to conserve power anyway). You can get pretty far on analog-only, you might be able to save yourself from doing bussed sensors if you have a bunch of plants all together.