Stop watering your plants and start letting them water themselves. Screw the spikelike valve onto the mouth of the Cowbell’s 750-milliliter bottle, jam the bottle spike-down into your potted plant’s soil, fill the bottle with water, and cap it. Over the next two weeks, the valve inside the spike will keep the water in the reservoir suspended in a vacuum. As the dirt dries out, the pressure changes enough to open the valve and let water out, giving your plant what it craves. A 250-ml version called Cowbell Mini ($42) is available for lesser flora.