Production of rooted cuttings is affected by factors such as stock plant health and age, harvesting methods, cutting treatment (e.g., storage temperature, hormone application), and environmental conditions under which stock plants are grown and cuttings are rooted. Stock plants are managed to maximize the quantity and quality of cuttings for rooting by starting with juvenile or rejuvenated source material, optimizing physiological status of the stock plant through environment manipulation, and harvesting propagules from preferred parts of the stock plants only during certain seasons (Hartmann et al., 2002).
Age of a stock plant from which cuttings are taken can influence how readily cuttings root. Because cuttings taken from stock plants that are ontogenetically younger typically root more readily than those taken from older plants, it is advantageous for cutting producers to use stock plants in a juvenile phase. Cuttings from stock plants of suboptimal ontogenetic age can be slow rooting, have a poor rooting percentage, and result in reduced branching (Gibson, 2006).
Rooting compounds are applied to shoot cuttings to economically root cuttings of many species and cultivars. In some cases a rooting compound can be used to accelerate root initiation and to increase root number, uniformity, and quality (Dole and Wilkins, 2005). Coleus is a fast-rooting species that typically does not require rooting compound for adequate rooting. Because postrooting plant vigor is known to vary among coleus cultivars (Gibson, 2006), rooting compound may be useful to improve propagation success in cultivars with suboptimal rooting due to the influences of season of the year, cutting week within a propagation cycle (number of weeks from which a stock plant has been harvested) from the same stock plants, or stock plant age.
This study had two main objectives. The first was to determine if cutting quality and rooting success of ‘Stained Glass’ coleus are influenced by season, cutting week within a propagation cycle, and stock plant age. The second objective was to determine if treating ‘Stained Glass’ coleus cuttings with rooting compound improves rooting and rooted cutting quality when they are suppressed due to the effects of season, cutting week, or stock plant age.
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