Soil moisture sensor seems to power up the whole plant

Not sure how that would affect the readings. You are the first person I have come across that claims it needs a sock in order to work properly.

Oh no I am not. This is the most glaring one, but there are several: Soil Moisture Sensor "freezes" Also Capacitive Soil Moisture Sensor barely drops Values and so on... However this is completely outside the scope of my post.

Yes, It's not a commercial product, it's a hobby product.

Ouch. OK.

Won't the sensor degrade more quickly that way?

Not sure what you mean here.

This is an example: Turn off power to a moisture sensor except when reading values - Arduino Stack Exchange But I saw it first hand: powering these sensors all the time causes them to degrade very quickly. I saw it first hand.

The sensing part goes all the way up the where the electronics are.

No, there is a clear line drawn in the sensor that separates the "sensing" part and the circuit.