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 grow n in Israel under black shade nets. We are studying the possibility to mani pulate the nature of the vegetative growth of greens to improve the yield a nd quality desirable for various ornamental crops. The present paper summar izes the results obtained for Pittosporum variegatum grown under shade nets of various optical properties: green, red, blue, grey, black, and reflecti ve. The knitting density and design of the nets were adjusted to give the s ame transmittance of sunlight in the PAR (photosynthetically active radiati on, 400-700 nm) region. The experiments were carried out in a commercial pl ot. A single layer of 50% shade net covered the plot during the winter seas on, and two layers in the summer, according to common practice. Data were c ollected mostly during the second growth year. The main results obtained in cluded: (i) pronounced stimulation of branch elongation under the Red net; (ii) dwarfing under the Blue net; (iii) the Grey net markedly enhanced bran ching, resulting in "bushy", dense plants with short side shoots and small leaves; (iv) the reflective, thermal net (Aluminet((R))) enhanced long bran ching. The results were reproducible over two successive harvesting years. We suggest that the coloured net technology can be applied to enhance comme rcially desired plant responses, thus substituting for the use of growth re gulators or pruning.