The effects of various combinations of day and night temperatures and day lengths on dill were studied in environmentally controlled chambers. The concentration of essential oil in dill herb was hugest under the highest temperatures tested, but except for within the highest temperature regime, the longer photoperiod also increased oil accumulation. A high temperature was necessary for high oil accumulation under a short photoperiod. Herb yields were generally greater under a short photoperiod, but particularly at lower temperatures. Time to maturity was accelerated by longer photoperiods and by increased temperatures.
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