Description from Amazon
Blumat Classic (Jr.) Automatic Plant Watering Stakes for Watering Plants on Vacation, X-Large (6 Pack XL)
Take a vacation and let your plants look after themselves with authentic Austrian-engineered Blumat Juniors. These are the Original Blumats and are superior in design, material quality, and durability to counterfeit products. After years of testing, Blumat has created one of the most efficient and reliable automatic watering devices on the market.
The ceramic cone is porous and allows water to be absorbed and released when placed in wet and dry mediums, respectively. As water is drawn from the cone and into the growing medium this creates a vacuum which draws water from the nearby container of water. For tropical plants or plants that need more water, raise the reservoir to create additional head pressure (water pressure resulting from gravity), thus increasing the flow of the water. For cactus or plants that need less water, lower the reservoir to even with the plant to only allow watering when the medium is almost completely dry. Since the ceramic cone only releases small amounts of water slowly, your plants will not experience over watering (which can drown the plant) or under watering (which can result in stunted growth and root damage) thus encouraging prolific growth in all plants!
Blumat Juniors will only draw water up to 12 inches from below the cone. If the surface of the water in your reservoir is lower, the flow of water will be restricted and the plants will dry out. In some cases, several cones may be necessary for larger plants to meet higher water needs. In this case, a larger reservoir should be used.