As alluded to above, your Pennywort's water needs will repeatedly change throughout the seasons. During most of spring and summer, you should water your Pennywort about once every week. As the heat of summer arrives, you should plan to increase your watering frequency to once or twice per day. In the late summer and fall, towards the end of the harvest period, you can reduce your watering frequency to about once per week. After harvest has ended, you can cease watering as your Pennywort has reached the end of its life cycle and will require no further soil moisture.
The maintenance schedule of Pennywort will require you to alter the amount of water you provide depending on the plant's current growth stage. Early on, especially if you grow your Pennywort from seeds, you'll need to provide water often enough to maintain consistent soil moisture, which encourages root development. When the plant becomes old enough to produce flowers, it will likely need even more water. During the fruit development growth stage, your Pennywort will likely need the most water out of any growth period, at times requiring water more than twice per day. Following that phase, the water needs of Pennywort will decline significantly.