Without thinking twice, we decided to change the design of the board. First, instead of two probes with galvanic measuring we used one with capacitive measuring. Then we made the top in the form of a leaf. And finally, we switched to the green color of the PCB - quite an obvious decision that yet took us some time! 

Components remained mostly the same - design based around atmega328 with LiPo rechargeable battery, and IR LED for sending out measured data. Our motivation was to keep it extremely cheap in production - although when implemented, it became evident that IR data link is not really convenient for this purpose.

The photos show that uPlant is now indistinguishable from a plant!