“…This considerable development in the ornamental use of H. macrophylla was made possible thanks to the great number of agronomic experiments carried out over the past 30 y. They have shown the influence of water restriction (Cameron et al, 2006;Morel, 2001), root volume restriction (Yeh and Chiang, 2001), temperatures (Adkins et al, 2003;Bailey and Weiler, 1984;Post, 1942;Vidalie, 1986), photoperiod (Guo et al, 1995;Morita et al, 1980;Shanks et al, 1986), light intensity (Bailey et al, 1987;Dugardin and Balemans, 1991;Rusch et al, 1986), plant growth regulators (Bailey et al, 1986;Joustra, 1989;Morita and Osuka, 1981) and relative air humidity (Codarin et al, 2006) on plant de- velopment. These experiments made it possible to capitalise on knowledge about existing interactions between plant development and certain environmental factors.…”