Illumination is the source of all life activities. The light on the earth comes from the sun. The sun is the most important condition for all living things in the world. Sunlight strikes the atmosphere through the atmosphere and produces two effects, namely thermal and light effects. (I) Types of light The most important influence on flowers in sunlight is visible light, ultraviolet light and infrared light. 1. Visible light is the energy of flowers for photosynthesis. From the seven-color light band of sunlight, chlorophyll absorbs red orange light and blue violet light most, and green light is almost totally reflected, so the leaves are green. In order to cultivate high quality flower seedlings, it is better to cover the nursery with light blue vinyl plastic than the white film. For example, orchids grow fast and strong under blue light. 2. Ultraviolet light is invisible light other than violet light and cannot pass through ordinary glass. Long-wavelength ultraviolet light can promote seed germination and facilitate flower coloration. For example, the camellias grown in Yunnan are particularly colorful. The shorter wavelength part can not only restrain the flowers but also kill the pathogen spores and increase the seed germination rate. 3. Infrared light is invisible light other than red light. It is a hotline that can detect its existence. It can increase the temperature and temperature of the land and provide the heat needed for flowers. When sunlight shines on a plant body, there is direct light and scattered light. The sunny daylight consists of direct light and scattered light. In cloudy days, only scattered light is present. Scattered light is generally beneficial to flower cultivation. Excessive direct light tends to be harmful to flowers. If the plants lack light or lack of light during the growth period, the symptoms are very obvious. That is, the stems and leaves have poor growth, are weak, and the flowering is not flourishing or flowering. (2) Illumination time The illumination time that affects the growth and development of flowers refers to the time that the sun shines during the day, from sunrise to sunset. The law of alternating day and night changes is called photoperiodism. Under natural conditions, opening orchids in spring and opening chrysanthemums in autumn are mainly affected by the photoperiod. According to the response of the flower to the photoperiod, it is often divided into three categories: long-day flower, middle-day flower and short-day flower. Long-day flowers are mostly temperate or frigid flowers. Generally, it takes more than 12 hours of light every day to bloom. Such as northern spring and summer flowering snapdragon, bowl lotus and so on. Short-day flowers include most tropical and sub-tropical flowers, which can be buddling and blooming only when the light is less than 12 hours a day. Such as the northern autumn and winter flowering poinsettia, chrysanthemum and so on. The buds and blossoms of flowers in China sunshine do not require strict sunshine, and the length of the night has no obvious effect on the formation of flower buds. Such as carnation, cyclamen, petunia, geranium, dianthus and so on. The use of the characteristics of flowering and flowering requires the length of illumination, which can artificially control the flowering period and enable the flower to bloom earlier or later, reaching the annual supply of potted flowers. (C) Illumination Intensity Illumination intensity refers to the energy of visible light received on a unit area, often expressed as lux (1x). According to the requirements of light intensity of potted flowers, they are often divided into three categories: positive flowers, negative flowers, and neutral flowers. Positive flowers generally grow robust under strong sunlight and grow and develop under light conditions. Such as one or two years of flowers, rose, chrysanthemum, jasmine, bowl lotus, poinsettia and so on. Negative flowers are flowers that are suitable for growing under insufficient light or under scattered light conditions. Can not stand strong light, generally in the shade of 50% or more under the weak light, normal long development. Such as the Guanyin lotus, lotus leaf Qiu Haiqi, mosaic, lotus leaf, kidney fern, velvet bamboo and other. Neutral flower refers to a plant that grows best when there is sufficient sunlight, and does not weaken when it is slightly shaded. Such as Fusang, Changchun, New Guinea Impatiens, Geranium, Belgian Rhododendron and so on. In general, potted foliage plants require low light levels. Under strong light, the leaves thicken and the leaf color fades, making it easy to burn. Potted plants require sufficient sunlight to form buds and bright colors.