Abstract: Plants are optimally grown under artificial narrowband Photosynthetically Active Radiation (“PAR”) of multiple colors, and color palettes, applied in but partially time-overlapping cycles. As well as a long, growing season, cycle, the colored lights are cyclically applied on a short, diurnal, cycle that often roughly simulates a peak-season sunny day at the earth latitude native to the plant. Bluer lights are applied commencing before redder lights, and are likewise terminated before the redder lights. Infrared light in particular, is preferably first applied at a time corresponding to early afternoon, and is temporally extended past a time corresponding to sunset. The colored lights and light palettes preferably rise to, and fall from, different peak intensities over periods from 10 minutes to 2 hours, and relative peak intensities of even such different colors as are used at all vary up to times two (×2) in response to differing PAR requirements of different plants.