Many horticultural crops require photoperiodic manipulation to initiate flowering and obtain a salable product when grown out of season. The current studies aim to reevaluate two common photoperiod manipulation practices by using light emitting diodes (LEDs) innate production of narrow bandwidths of light and their instantaneous output regulation. Night interruptions (NI) with varying amounts of narrow bandwidth far-red (FR) (peak at 730 nm) were unable to promote flowering of the short-day plant Chrysanthemum morifolium. Far-red light caused shade avoidance syndrome (SAS) late in skotoperiods when circadian-controlled internal factors are most abundant. Cyclical NI with simulated irrigation booms slightly hastens flowering of the long-day plant Petunia hybrida while causing no reductions in number of inflorescence. An industry standard of 4-hrs of continuous NI resulted in faster flowering and more inflorescences than any cyclical NI frequency tested. Both novel night interruption approaches need refinement for more realistic use.
