Coloured shade-nets influence stem length, time to flower, flower number and inflorescence diameter in four ornamental cut-flower crops

The effect of coloured shade-nets on the growth characteristics of several ornamental crops for the cut flower industry was tested. Overall, seven cultivars of four different species (lisianthus, sunflower, Trachelium, and Ornithogalum) were grown under four different coloured nets. There was a marked impact of net colour on flowering stem length and cut flower weight in three of the four species. Compared to the black, neutral net, growth under red and yellow coloured shade-nets caused a significant increase in flowering stem-length in three lisianthus and two sunflower cultivars. This increase in stem-length was accompanied by an increase in cut flower weight in the lisianthus cultivars grown under the yellow net. Plants grown under the blue net had a shorter stem-length in two sunflower cultivars and in Trachelium. This effect was accompanied by a lower weight of Trachelium cut flowers grown under the blue net. The diameters of Trachelium and sunflower inflorescences were smaller, and those of lisianthus were shorter, when grown under the blue net. The red net caused a significantly shorter time to flowering in Ornithogalum, even when accompanied by the use of the chemical growth inducer, gibberellin GA(3). The consistent, cross-species effects of coloured shade-nets may have important consequences for the cut flower industry.