There are many reasons why plant cuttings fail. Either it did not root because it was too small or the root system is too weak to survive the environment it is placed in., or too much light Plants require a certain amount of light, which they use for photosynthesis, to grow and form roots. When plants are exposed to too much light, they become leggy and spindly. This is caused by a lack of chlorophyll. A change in the weather can have an effect on plant growth. For example, when the temperature rises, plants will often become more active.