Coloured shade nets can improve the yield and quality of green decorative branches of Pittosporum variegatum

Many green decorative branches ("greens"), which form an important part of ornamental bouquets, originate from shade plants, and are commercially grown in Israel under black shade nets. We are studying the possibility to manipulate the nature of the vegetative growth of greens to improve the yield and quality desirable for various ornamental crops. The present paper summarizes the results obtained for Pittosporum variegatum grown under shade nets of various optical properties: green, red, blue, grey, black, and reflective. The knitting density and design of the nets were adjusted to give the same transmittance of sunlight in the PAR (photosynthetically active radiation, 400-700 nm) region. The experiments were carried out in a commercial plot. A single layer of 50% shade net covered the plot during the winter season, and two layers in the summer, according to common practice. Data were collected mostly during the second growth year. The main results obtained included: (i) pronounced stimulation of branch elongation under the Red net; (ii) dwarfing under the Blue net; (iii) the Grey net markedly enhanced branching, resulting in "bushy", dense plants with short side shoots and small leaves; (iv) the reflective, thermal net (Aluminet((R))) enhanced long branching. The results were reproducible over two successive harvesting years. We suggest that the coloured net technology can be applied to enhance commercially desired plant responses, thus substituting for the use of growth regulators or pruning.