After planting, North American forcers generally have several species in a cooler, principally tulip, daffodil and hyacinth. While the basic cooling requirements for these species is compatible, in recent years it has become more common to drop the temperature in the cooler more rapidly than in the past to minimize tulip root growth to reduce Trichoderma problems for late forcings. Tulip roots grow rapidly at 48F (9C), and to a lesser extent at 40F (4C), while 33F (1C) severely reduces tulip root growth. Since Trichoderma problems commonly occur in very heavily rooted plants, a rapid reduction of temperature has been suggested as an easy way to reduce excessive tulip root growth. However, when hyacinth and Tete-a-Tete are in such coolers, they are exposed to temperatures that are substantially lower than optrimum, and it has been noted that hyacinths and Tete-a-Tete often grow very slowly after being cooled in “cold” coolers.
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