These little 'carrots' will help ensure proper moisture levels in the garden by 'feeling' how moist the soil is. The Blumat drip emitter is designed to open and close a valve according to how much water is in the soil or other medium.
It works best with a gravity fed reservoir system. Put the reservoir higher than the plants, connect the drip lines to the res, and then the Blumat carrots will control when to add more water.
They can be adjusted to stop at any level, as some plants like really wet and others just a slightly damp environment.