There are a variety of things needed for successful plant growth, and I'll go through them in more detail below.
Plants require water to remain healthy and grow, and this is usually accomplished through the root system. Plants draw moisture from the ground, alongside the nutrients from the soil itself, and these nutrients are used to help the plant grow.
Light
Another important factor in plant growth is light. It's function is to activate the process known as photosynthesis, which is the conversion of light into energy. This is a huge part of a plant's growth cycle, and too little sunlight can stunt the plant's growth, and even allow it to wither.
Soil
Plants require nourishing soil, so it's an important factor in the growth process to have healthy, clean soil.
Air
Air is often overlooked in the process of plant growth, but it's a really significant element. Air that's filled with pollutants such as cigarette smoke hinders a plant's ability to absorb sunlight.
How does it all work together?
Putting all the piece together, plant growth works as plants absorb water and nutrients from healthy soil. When a plant is healthy it can then absorb enough sunlight to convert to energy to grow.
Here's a really useful video that breaks down the process of photosynthesis, which sis imperative for successful plant growth:
