The propagation of cuttings often takes place in late winter, early spring, when light levels are low. An experiment at Purdue University confirmed that the use of supplemetary light to bring the daily light integral (DLI) to between 8 and 10 mol_m-2_d-1 provides the best conditions for rooting cuttings. A DLI of 1mol_m-2_d-1 means the number of moles of light (mol) per square meter (m-2) per day (d-1). A mole represents 6.022 x 1023 photons of light. The total shoot and root mass increased from 50% to over 400%, depending on species, when the DLI was increased. Over the same period, quality inceased from 176 to over 800%. The period of the light application was 14 days with supplementary light being given for 16hrs each day. Not only do higher light levels improve the quality of rooted cuttings, they also speed up rooting time (production time), therefore increasing profitability also through the possibility of starting another crop earlier. For further information: Roberto Lopez, E-mail: rglopez@purdue.edu

http://www.purdue.edu/newsroom/research/2012/120123LopezBedding.html

Cuttings were taken from a range of bedding plants varieties of nine different species. They were subsequently propagated under glasshouse conditions with an air and substrate temperature of 23°C. “Growth, Morphology, and Quality of Rooted Cuttings of Several Herbaceous Annual Bedding Plants Are influenced by Photosynthetic Dalily Light Integral During Root Development”, C.J.Currey, V.A.Hutchinson and R.G.Lopez, Purdue University. HortScience 47 (1):25-30. 2012.

http://hortsci.ashspublications.org