Various techniques have been used to control the height and branching of pot plants.
Some have required chemical growth regulators, others have used abrupt drops in temperature, while yet others have used changes in light quality. In the experiments reported here, the plants were grown under a pearl-coloured polyethylene net which increased the proportion of light that was scattered without changing its spectral quality.
Uniformly rooted plantlets of Myrtus communis and Crowea 'Poorinda Extasy' were placed in one of two walk-in tunnels. One tunnel was covered with the pearl-coloured shade net while the other was covered with a black one. The black net was constructed of strands that transmitted no light while the strands of the pearl net were semi-transparent. The density of strands was adjusted so that both nets provided 50 per cent shading. It was then found that the black net scattered 11 per cent of the light while the pearl one scattered 62 per cent.
Plants of Myrtus grown under the pearl net were significantly shorter and smaller in diameter and had more branches than those grown under the black net. Although the Crowea plants did not respond in the same way, those under the pearl net had many more flowers per branch.
Light-scattering Shade Net Increases Branching and Flowering in Ornamental Pot Plants by Nissim-Levi, Farkash, Hamburger, Ovadia, Forrer, Kagan and Oren-Shamir (2008). Journal of Horticultural Science & Biotechnology 83 (1): 9-14. The authors' abstract of their manuscript can be seen in full at www.jhortscib.com.