The gardeners who have a raised bed of stone or concrete, can try the following solution:
First stick a weather-resistant tape on the stones or concrete. The surface must be thoroughly cleaned and dried first.
Then stick two parallel aluminum strips at a distance of about 2 to 3 mm. Then connect to the controller.
Suitable adhesive tape can be found in our Online Shop
Other option is to paint the external walls with good adhering varnish then stic the aluminum strips as usual at a distance of 2-3 mm and connect with the controller.
These solutions have been used successfully by some of our customers.