Effect of Photoselective Shadecloth and Plastic Film on Growth of Chrysanthemums under Supplemental Lighting

Abstract

Controlling plant height is an important practice in the ornamental plant industry. With high cost of growth regulators and concern about their environmental aspects and health of workers, alternative ways of controlling growth may be advantageous. Objective was to determine effect of photoselective shadecloth and plastic film on growth of `Barbara', `Shasta', and `Chesapeake' mums under supplemental lighting. In experiment 1, `Barbara' plants (two and four weeks old) were placed under either wide spectrum fluorescent lamps and incandescent light bulbs (control) or lights covered with photoselective shadecloth. In experiment 2, 3-week-old `Shasta' and `Chesapeake' plants were placed under lights or lights covered with photoselective plastic film. Effect of shadecloth differed with age of `Barbara' plants. For 1-month-old plants placed under lights, stem diameter, stem dry weight, and root dry weight were reduced under shadecloth compared to control. No differences were observed for plant height, pot height, leaf number, leaf area/plant, and leaf dry weight. For 2-week-old plants, leaf number, leaf area/plant, leaf dry weight, and stem dry weight were less under shadecloth than control. No effects on plant height, pot height, stem diameter, and root dry weight were observed. Plastic film reduced plant height and pot height for `Shasta' and `Chesapeake' plants and reduced stem dry weight and total plant dry weight for `Shasta'. No differences were seen for other growth measurements. This study indicated photoselective shadecloth did not control height of `Barbara' and its effect on growth was influenced by plant age. Photoselective plastic film controlled height of `Shasta' and `Chesapeake' and offers an alternative method for growth control of mum plants.