In the experiments described here, four coloured shade-nets were used to cover four different ornamental crops growing in net-houses.
One net was made from opaque black threads while the others were made from semi-transparent red, blue or yellow threads. All four nets were adjusted to transmit the same amount of light but the semi-transparent ones also altered its spectral composition. The experiments were conducted in the Negev Desert, Israel, where plants of Trachelium 'Purple Winter', Eustoma grandiflorum, Helianthus annuus and Ornithogalum dubium Award of Garden Merit (AGM) were grown under each of the shade-nets. The red, blue, and yellow shade-nets had no effect on the flowering times of E. grandiflorum, H. annuus and 'Purple Winter'.
The most striking effect on the three species was that the shortest stems were found under the blue shade-net. With E. grandiflorum, the longest stems were found under the yellow and red shade-nets. The shade-nets had little effect on the stem length of O. dubium AGM but the plants under the red shade-net flowered before those growing in any other treatment.
Coloured Shade-nets Influence Stem Length, Time to Flower, Flower Number and Inflorescence Diameter in Four Ornamental Cut-flower Crops by Ovadia, Dori, Nissim-Levi, Shahak and Oren-Shamir (2009). Journal of Horticultural Science & Biotechnology 84 (2): 161-166.