Water is held in the bucket, and released as the clay spike becomes dry.
This Smart Pot has sprouted sunflowers.
Blumat bucket fitting
To attach the fitting to the bucket, a hole needs to be made.
A hot soldering iron can make holes in plastic buckets easily and without splitting.
Here the Blumat bucket fitting is installed
The Blumat spike should be filled with water and soaked for an hour before use. The cap on top adjusts the watering level, so should be set to shut when wet, and open when dry.
I haven’t had the pleasure of trying these before, but the concept seems very cool. If they work well, it could be very useful in areas where water has to be carried and left.