(69) Effects of Photoselective Shadecloths on Growth and Flowering of Potted Chrysanthemum

Abstract

Controlling plant height is an important practice in the ornamental plant industry. Though commonly used, growth regulators are expensive, and there are concerns about environmental consequences and safety of workers. Alternative ways of controlling growth may be advantageous. The objective of this study was to determine the effects of photoselective shadecloths on the growth and flowering of `Arezzo' chrysanthemum. One-month-old potted `Arezzo' chrysanthemum plants were grown in a saranhouse in chambers built with PVC (polyvinyl chloride) pipe covered with 30% shadecloths—red, blue, gray, and black (control). The blue shadecloth was more effective in reducing plant height, with no differences among the other shadecloths. Plant canopy dimensions—greatest canopy width and average canopy width—did not show any differences among the shadecloths. The red shadecloth was more effective in hastening flowering, followed by the blue shadecloth. This was evident by flowering first occurring with the red shadecloth and initially the greatest number of buds showing color. Additionally, the red shadecloth had the highest proportion of the number of flowers to the combined number of flowers and buds showing color. Specifically, the total number of flowers was similar to the total number of buds showing color. In contrast with the other shadecloths, there was a greater number of buds showing color than the number of flowers. The most buds showing color occurred with the gray shadecloth. The three shadecloths resulted in a greater number of the combined buds showing color and flowers than the black shadecloth. In conclusion, photoselective shadecloths may provide an alternative to controlling plant height and altering the flowering pattern of potted chrysanthemums.