THE PHYSIOLOGY OF FLOWERING IN LILIUM

The environmental requirements for floral induction, initiation and development are well known for Lilium longiflorum. The purpose of this paper is to review and compare the information know for L. longiflorum, which is vast, to the scant information for the ‘Asiatic’, ‘Oriental’, their hybrids, and other species.
A cold treatment of 4.5–7.5°C for 6-weeks in a moist environment is optimal for L. longiflorum. Generative apices are not microscopically evident until shoots have emerged, are some 10–15 cm tall and some 30–40 days after being forced at 20°C. However, this is only one of four classifications as to when flowers are initiated with the various species.
The four groups may be defined as follows: Group I. initiates flowers in late summer and buds are fully developed by autumn; Group II. initiates flowers in late summer, but development does not occur until after a cold treatment (spring); Group III. commences floral initiation after the cold treatment, prior to emergence, and Group IV. as described above for L. longiflorum. Cold may be considered a requirement for shoot elongation.
With L. longiflorum flowering will occur at temperatures below 20°C. Long days can partially substitute for cold once shoots emerge.

VII International Symposium on Flowerbulbs

H.F. Wilkins, J.M. Dole

https://doi.org/10.17660/ActaHortic.1997.430.25