Timing of a Short-Term Reduction in Temperature and Irradiance Affects Growth and Flowering of Four Annual Bedding Plants

Timing of a Short-Term Reduction in Temperature and Irradiance Affects Growth and Flowering of Four Annual Bedding Plants

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Heating and supplemental lighting are often provided during spring greenhouse production of bedding plants, but energy inputs are a major production cost.Different energy-savings strategies can be utilized, but effects on plant growth and flowering must be considered.We evaluated the impact and timing of a two-week low-energy (reduced temperature and irradiance) interval on flowering and growth of impatiens (Impatiens walleriana Hook.f.‘Accent Orange’), pansy (Viola × wittrockiana Gams.

‘Delta Premium Blue Boardshorts Blotch’), petunia (Petunia × hybrida Hort.Vilm.-Andr.‘Dreams Pink’), and snapdragon (Antirrhinum majus L.‘Montego Violet’).

Flowering was delayed 7 to 10 days when the low-energy exposure occurred before flowering.Flower number was reduced 40⁻61% in impatiens, 33⁻35% in petunia (low-energy weeks 5⁻6 and weeks 7⁻8, respectively), and 35% in pansy (weeks 5⁻6).Petunia and impatiens dry mass gradually decreased as the low-energy Makeup Sponges exposure occurred later in production; petunias were 26% (weeks 5⁻6) and 33% (weeks 7⁻8) smaller, and impatiens were 20% to 31% smaller than ambient plants.Estimated energy savings were 14% to 16% for the eight-week period, but only up to 7% from transplant to flowering.Growers can consider including a two-week reduction in temperature and irradiance to reduce energy, provided an additional week of production is scheduled.