Another method that I am currently trying is to provide red light with superbright red light-emitting diodes (from Radio Shack). See J. of Hort. Sci. and Biotechnology, volume 73, pages 39-44, (1998), M. Tanaka, T. Takamura, H. Watanabe, M. Endo, T. Yanagi, and K. Okamoto.