This depends on the type of plant, size of plant, and how many plants you are trying to grow. A single light might be appropriate for a small pot with a single plant or a small seedling tray. As plants get larger or the required coverage area expands, more lights may be needed. Generally, if plants are growing well and have a compact, robust structure, they are getting enough light. If plants are weak, with elongated stems and many small leaves, this may indicate additional light needs to be provided. When the knob is in the EXT state, it can be networked to control the joint dimming of lamps. A maximum of 60 LED grow light lamps can be connected to one controller using a daisy chain setup. Up to 500 lamps per daisy chain can be connected using splitters, which is beneficial for large area of indoor growing and commercial planting.