PLANTS PLANTS AND LIGHT PLANTS AND LIGHT When plants get bigger we say they grow. Plants need light for them to grow. Plants use light to make food with no light then plants will be unable to make food. With no food plants become weak,unhealthy and they might die. Look at the two plants on the side. The plant with water and light is very healthy. The plant with water but no sunlight is very unhealthy. Sunlight is very important to plants