Gardener's Dictionary: Water bulb
Water bulb (n): Also called water sticks, water bulbs are decorative watering devices for container plants (usually indoor plants). The water bulbs, which are filled with water and stuck into the soil, slowly and constantly water the plant. Water bulbs are useful especially when a gardener leaves for an extended period of time (they can water plants for up to six weeks without being refilled). There are reusable and disposable types of watering bulbs.
