Photoperiod

Photoperiod refers to the length of day and night—that is, the amount of light a plant receives over a 24-hour period. Tomatoes are not plants that are highly dependent on day length, but the amount of light does affect their growth rate, flowering, and yield. In practice, the total amount of light energy reaching the plants is more important than the photoperiod itself. When using supplemental lighting, do not extend the lamp’s operating time indefinitely; instead, evaluate it in conjunction with PPFD and DLI.