Growth is a natural process . All living beings (plants + animals) grows and reach to their optimum height. Growth is also one of evidence of being alive.
Basically, plants grows taller when they get all their basic needs. Their basic needs include:-
1. Water
2. Sunlight or warmth
3. Required nutrients.
Plants have ability to make their own food in the presence of sunlight and the process is called as" photosynthesis". They also have transportation system that delivers food and water to every shoot and root of the plants. This this way they get nutrients and water. But , talking about height, it totally depends upon the surrounding competition for sunlight required for their growth.
For example:-
1. Plants such as chrysanthemums and swamp sunflower grow taller in partially shaded areas.
2. But , plants like blue Flag requires full sunlight to reach to their optimum height.
Thank you!!