Why Are High Pressure Sodium Lights Good for Flowering?
High pressure sodium lamps are typically used in applications such as parking lots where color of the lighting is less important, such as street lighting as well as for supplemental greenhouse lights. High pressure sodium (HPS) lamps have the advantage of enhancing the fruiting and flowering process in plants. The spectrum of orange/red light that HPS produces is what plants use in their reproductive processes, which in general will produce larger harvests of higher quality flowers or fruits. The problem with growing under HPS alone is that plants grow to be taller with a longer internodal length than plants grown under metal halide lights which produce a bluer spectrum. Another downside to HPS is that plants may not appear very healthy growing only under these lights. High pressure sodium bulbs emit yellow lighting (2200K) and thus have a poor color rendering index of 22.
