Asiatic lily is one of three types of lilies which are commonly grown; the other two are Easter Lily and Oriental Lily (1). There are many species that are grouped together as Asiatic lilies, such as the Lilium amabile, which has red flowers, Lilium bakerianum, which grows at high altitudes, the tall Lilium callosum, and the mildly scented Lilium cernuum(2).
Asiatic lilies are commonly bred as potted plants rather than for cut flowers. There are also many hybrids which are produced by interbreeding it with the other types of lilies, in which case lines derived from Asiatic lilies may have some of its characteristics and requirements.
Whether they are grown as potted plants or for cut flowers, it is quite common to force lilies to bloom at a planned time like Easter or Christmas. In these cases, the Asiatic lilies are grown indoors in winter to bloom at times that do not coincide with their natural flowering season, which is late spring to early summer (1, 3).
The process of growing lilies, especially forcing them requires detailed and specific requirements in terms of planting depth for the bulbs, watering, potting media, and maintenance of temperature and lighting.
Light is important to control the growth and development of the plant, beside influencing its flowering, as Asiatic lilies are long-day plants. Regardless of the colour, insufficient duration of lighting causes weak growth in plants making them long and limp, and produces lighter coloured foliage. To ensure proper vegetative growth, supplementary lighting should begin early at a light level of 6,000 lux (4).
A simple combination of blue and red light can be used during the vegetative growth stage. Blue light increases photosynthesis rate, and even though red light is the one which is mostly absorbed by chlorophyll, too much red is harmful to the synthesis of chlorophyll. The presence of blue lights will keep the plant compact a desirable trait when trying to force Asiatic lilies (5).
LED lights used in the combination of white, red, blue, and orange in the ratio 3:8:5:2, made plants grow faster than under natural light (6).
The length and intensity of lighting are also very important to ensure proper flowering in Asiatic lilies. It is a long-day plant and requires more hours of day light compared to darkness to be able to produce flowers. These photoperiodic requirements of the Asiatic lilies must be taken into consideration, in combination with the geographical location, or the light admitted into the greenhouse while growing them (4).
It is bud formation and flower development that are impacted by insufficient intensity and length of light in Asiatic lilies. Flower buds which are formed will drop when they do not receive enough hours of light; this light deficiency can also lead to late flower bud desiccation and reduce keeping quality (3). Since Asiatic lilies are popularly forced to grow during winter months when natural day light is available for a short time in temperate regions,
it is important to provide supplementary light in winter to achieve the proper photoperiod or day length needed by the lilies for bud development and flowering (4).
By using LED grow lights in the combination of white, red, blue, and orange in the ratio 3:8:5:2 it was possible to extend growing time by 8 hours each day to achieve 14 hours photoperiod day, which in turn shortened the flowering time needed for two cultivars by 5 days. Moreover, this can increase the number of flowers per stem in some varieties as well (6).
It takes 30 days from bud emergence to bud elongation and another 30 days before they reach a market stage where the bud is fully grown and coloured, but still closed (3). The latest time to start the use of supplementary lighting to prevent bud abortion is when the flower buds are about 1 cm in size (4). The minimum light intensity which is then recommended in the greenhouse for Asiatic lilies and its hybrids is ‘300 Wh/m² or 190 Joules/cm²/day (in terms of PAR= Photosynthetically Active Radiation)’ or 3200-3300 lux(4). A combination of red and far-red is as good as white light for providing daylight lighting (7).
There are two novel features of flowering in Asiatic lilies. One is that they open completely in four hours, and the second feature is that it is controlled not just by the number of hours of light, but by the cycle of light and dark. It is important to remember that its flowers require a long period of darkness before the buds start opening. The opening of flowers is initiated in darkness for about two hours, and the flower opens completely two hours after dawn regardless of the day-length (7). White light can be used to supplement daylight; another option is the combination of red with far-red for daylight lighting (7).
Other Colour LEDs
Including white light makes it easier for people to work with the plant and identify disease symptoms (5). To control an outbreak of diseases use UV radiation to help in controlling them (8).
Extend Natural growing Seasons for More Profits
The process of growing flowering plants the year around in any climatic conditions has been made easier with LEDs. Moreover, colour rendering solves specific problems associated with each kind of flower. Photoperiodism, the top concern in Asiatic lilies, is being solved by LEDs by improving bud formation and development as well as flower timing.