This little one-inch moisture indicator is great for indoor plants that need to be watered whenever the surface soil is beginning to dry or is dry already. That includes almost all ferns, cyclamen, pileas, peperomias, even philodendrons and palms. Simply work a wrox tablet down into the surface soil until it is slightly submerged. Water the pot thoroughly, including the wrox, until water runs out the bottom of the pot. The wrox should turn a deep blue. As it dries out, it will gradually fade to white. When it does, time to water again. According to the manufacturer, these tablets can be reused countless times. Easy, eh?