Effects of colored shade nets on various quality aspects of pansy (Viola x wittrockiana)

Garden pansies (Viola x wittrockiana Gams ex Nauenburg & Buttler) are a greenhouse crop commonly grown under black shade net, and often require the use of chemical plant growth regulators to maintain a compact growth habit. Non-chemical efforts to alter plant morphology, like height, would provide a more sustainable solution than chemical application. The objective of these studies was to evaluate the effects of different colors of shade nets on growth and flowering of pansies. In the first experiment, pansies ('Clear Yellow', 'Buttered Popcorn', and 'Deep Orange' were placed under 30% blue or black shade net, or a control with no shade net. In the second experiment, pansies of the same three cultivars were grown under 50% black, red, pearl, or Aluminet shade net. Data were collected on plant height, plant width, flower number, plant survival, SPAD readings, and light quality. In experiment one, the blue shade net reduced height to flower and height to leaves, but also decreased flower number and plant survival as compared to black shade net. All plants under no shade died. In experiment two, SPAD, an indicator of plant quality, was found to be lower under black shade net, while pearl shade net led to a decrease in plant height and no effect on number of flowers. Light quality, including R:FR ratio, varied among shade treatments, while light intensity was reduced under Aluminet, black (50%), and red shade nets compared to other shade treatments. Blue and pearl shade nets both reduced plant height, but blue shade net also reduced plant survival and flowering