Since I don’t want to have people touching plants *all* the time, I want to have input via breath – as mentioned earlier.
But what if I want to rely on some touching? Then I run into the problem that touch is binary.
I guess I also want to build this: http://www.instructables.com/id/Touche-for-Arduino-Advanced-touch-sensing/

or engarde: http://spritesmods.com/?art=engarde

update: build the „touché“. it’s working wonderful on a water bottle, but no response on a plant yet.