[0008] U.S. Pat. No. 3,775,904 to P

[0008] U.S. Pat. No. 3,775,904 to Peters (1973) reveals a self-watering flowerpot that has double walls. The control for the release of water from the reservoir is not by a soil moisture sensor. A cavity and a channel, both open downward, are placed at the bottom of the pot. An aperture in the cavity allows water to seep into the soil by capillary action. The released water creates a vacuum in the reservoir and stops the water flow. The vacuum is relieved when the soil is sufficiently dry to let air permeate through the aperture and to the water chamber. Other patents for self-watering planters include U.S. Pat. Nos. 4,864,711 to Fah (1989), 4,819,375 to Baumgartner at al. (1989), 4,885,870 to Fong (1989), and 4,916,858 to Hobson (1990). All the self-watering planters share the same disadvantages as described earlier for U.S. Pat. No. 6,134,833.