The effect of Supplemental Light Source, Illumination and Quantum Flux Density on the Flowering of Seed-Propagated Geraniums

SummaryThe time required for flowering of four cultivars of F1 seed-propagated geraniums (Pelargonium χ hortorum Bailey) grown under different quantum flux density levels (27 or 54 μ E m-2 s-1), illuminations (2.7 or 5.4 klx) and durations (2, 4 and 6 weeks) of high pressure sodium (HPS) and low pressure sodium (LPS) light were compared with plants grown under ambient light. Days from seeding to flower were reduced for all cultivars with HPS light, but days to flower were not reduced by LPS treatment for any cultivars compared with the control plants. Cumulative supplemental quanta (E m-2) for HPS light only was significantly negatively correlated with days to flower for three of the cultivars, indicating the value of supplemental HPS light at an early stage of plant development.