Pennsylvania Flower Growers #141
Much has been written on the causes of calyx splitting in carnation. The percentage of split calyxes has been recorded for almost every cultural experiment published on carnations. A review of the literature on carnations indicates that almost everything influences calyx splitting. Since it is recognized that the problem is due to a number of causes, several of which interact at times, there is a need for some clarification on this subject. Since some varieties split more than others, the genetic factor was indicated as a contributing cause at an early date. Wagner (7) selected 12 splitting and 12 non-splitting plants from the variety Frosted Patrician. From February to May of the following year the "non-splitting" plants produced 11 per cent split calyxes while the "splitting" plants were producing 29 per cent. Selection work within the Sim varieties at Colorado State University (2) has shown that it is possible to select away from, or for calyx splitting. Selections made which are free from calyx splitting have fewer petals and are normally hollow centered. Early writers on carnations recognized fluctuating temperatures as a primary cause of calyx splitting. Szendel (6) caused splitting on the varieties Sophelia and Spectrum Supreme by lowering the night temperature occassionally 10° F below that normally used. Short temperature periods at wide intervals of time increased splitting more than frequent low temperature treatments. The colder the environment, the higher was the percentage of splits. Szendel also found that a prolonged period of extremely low temperatures increased significantly the number of petals.
Keywords: Temperature control Genetic factor Fast temperature drops Delay of heating Soil nitroge