This practice is not needed when forcing during cool months but is particularly useful when forcing during warmer months. Lily height is a function of light intensity. The higher the light intensity, the shorter the plant. Lilies planted in December or January for an Easter market will probably be taller than lilies planted in late February for Mother's Day. Be sure to allow more spacing between pots when forcing during darker periods to ensure that the crop stays short.
Asiatic hybrids are susceptible to bud abortion during periods of low light.
Some varieties are more susceptible than others, but in general supplemental lighting will reduce the incidence of bud abscission and bud blasting in Asiatic hybrids. The Oriental hybrids are not as prone to bud drop, however, the use of supplemental lighting will extend the daylength can reduce the forcing time by 3-4 weeks. In the Netherlands, supplemental photosynthetic lighting is used mainly for cut flowers scheduled during the winter months and in our country, some growers are starting to use supplemental lighting as well. Growing at improper temperatures will cause serious problems. Height control is one of the more difficult aspects of pot lily forcing.