Wait to water when you stick your finger into the soil up to the 2nd knuckle. If it's dry at that depth (about 1-1/2 inches), it's time to water. The amount is impossible to tell without knowing pots or no pots, type of soil, size of plants. At a wild guess, 1 cup for a 6" plant, then go from there. That's a minimum. Every 4 to 5 days.