Plants convert light into food through photosynthesis. Without light, they die. Sunlight is the most natural way of providing plants with enough light. Sunlight consists of a variety of different coloured rays of light, which can be seen by looking at the light through a prism. The visible light rays range from blue light to red light. Plants absorb all colours of sunlight, but only need certain colours to grow.

The colour of the light determines the light quality for the plant. If the light is of the right quality, this means that it contains the right colours that the plant needs to grow. If the plant receives poor quality light, i.e. light that does not contain the right colours, it will die over time. The plant's foliage needs blue light, the flowers red.

The right light colours must also have an adequate intensity and shine on the plant long enough for it to grow well. The intensity of the light can be recognised by its brightness. Artificial light sources can be intensified by moving the plant closer to the light source. This works particularly well with neon light, where plants grow well if they are only a few centimetres away. Weak light can be compensated for to a certain extent with longer exposure to light. 

Ordinary household lamps mainly produce red light beams. This light can only be used to support, but not exclusively for plants. In addition, household bulbs get too hot and the plant cannot be moved too close without burning. This reduces the light intensity and renders the light almost ineffective. Fluorescent tubes emit blue light, which the plant needs for its leaves. Fluorescent tubes are cool and can therefore come close to the plant for increased light intensity. Special plant lamps are usually fluorescent lamps with different light colours that allow plants to grow completely indoors without daylight.

Plants with poor lighting conditions usually do not grow at all or hardly at all. If only red light is used, the plants remain thin and develop small, discoloured leaves. Blue light alone ensures healthy foliage with the right light intensity, but the plant cannot flower under blue light. Other light colours do not promote plant growth at all, so a plant will not thrive under yellow and orange light alone and may even die.