A lighting device for supporting plant-growth includes an LED driver that inputs a high-voltage AC driver-input current. The driver outputs a driver-output current at a stepped driver-output voltage. LEDs are powered by the driver-output current. The LEDs include deep-red LEDs that output a first number W1 of radiation watts of a deep-red light band at 660 nm, far-red LEDs that output a second number W2 of radiation watts of a far-red light band at 730 nm, and white-light LEDs that output a third number W3 of radiation watts of white light having a color rendering index (CRI) of less than 75. W3 is greater than the sum L1+L2. At least 3% of all radiation output by the LEDs is at or above 700 nm.
