PILOT SCALE STUDY ON USE OF PHOTOPERIOD TO ENHANCE YIELD AND INFLUENCE TIMING OF STANDARD CARNATIONS

A four-year study of interaction between photoperiod, yield, and timing of the standard carnation 'White #1' was started June, 1985. This paper reports results of two planting dates, two pinching treatments, combined with short day treatments followed by dusk-to-dawn long days, on yield and grade over a 91-week period. The second two-year part is to begin with replanting and re-randomization Spring, 1987. There was a considerable effect of treatment position in the east-west oriented, fiberglass-covered greenhouse, with the southwest bench producing 40% more flowers over the second reporting period, compared to the second bench from the north wall. In the first production year, carnations, subjected to 45 short days, followed by 21 dusk-to-dawn long days, produced 1 to 2 more breaks per plant (28.1 plants m^-2), which resulted in higher yields, compared to non-treated plants. During the second year's production (to 14 Mar 1987), short-day treated plants again produced more flowers, but the treatment position could account for the difference. There has not appeared to be a highly significant effect of short-day treatment on increased carnation yield in the second production year, although long days have a distinct effect on timing of peak production.