Temperature, Supplemental Lighting, and Chloromequat Chloride Effects on Flowering of Geranium Seedlings

The time between sowing and flowering (crop cycle) of geranium Pelargonium × hortorum Bailey was affected by light, temperature, chloromequat chloride (CCC), and cultivar. A minimum daily light integral of 17 mol·d −1 ·m −2 , provided by high-pressure sodium lamps (HPS) prior to transplanting, accelerated flower initiation. HPS, low pressure sodium (LPS), and metal halide (MH) lamps, used as supplemental light after transplanting, reduced the crop cycle significantly compared to incandescent (INC) or natural light only. Crop cycles were similar among the HPS, LPS, and MH lamp treatments when equal-input lamp wattage was used per unit growing area, even though PPF values at the plant canopy varied. Plants grown at 21° and 27°C had a 5- to 15-day-shorter crop cycle than plants grown at 18° and 21°. Generally CCC reduced the crop cycle, but not consistently for all cultivar and lighting combinations. Chemical names used: 2-chloro- N , N , N -trimethylethanaminium chloride [chloromequat chloride (CCC)].