Water

• A tree, like most plant life, requires a significant amount of water to grow. Even trees that grow in arid environments require some form of water to sustain themselves. During a tree's first two years of life, it requires more water than ever because the tree is exerting most of its energy to grow. After the first two years, trees need just enough water to keep the soil moist --- but not soggy --- around the roots. According to the Arbor Day Foundation, trees need the soil to be moist at least 2 inches deep.
  
  

Soil

• For a tree to grow, the soil must be at least 3 feet deep, according to the Missouri Department of Conservation. When soil is at least 3 feet deep, it allows moisture to move through it but also retains enough moisture for the tree to thrive. The pH of the soil should be between 5.0 and 6.0 for the majority of tree species to survive.
  
  

Sunlight

• All plants, including trees, need sunlight to perform photosynthesis. Trees use this process to make food. Each plant species varies as to the amount of sunlight it requires to thrive. While some require direct sunlight for a minimum number of hours per day, others can survive in limited sunlight or even shade.
  
  

Air

• Although air surrounds trees in the environment, what is in the air is important for their survival. Trees thrive on carbon dioxide, which is present in the atmosphere. When a tree absorbs carbon dioxide, it releases oxygen, which is one reason trees and plants are important for a healthy environment. Enclosed areas will ultimately suffocate a tree, but open areas, where air naturally circulates, will allow trees to thrive.
  
  

Space

• Trees need space to grow. Not only do trees grow upward, but also the roots of trees grow outward from beneath the soil. Plant large trees, such as oaks, far enough away from building foundations, sidewalks and other areas where its roots may be prevented from growing. The area surrounding the planting location should be just as hospitable to the tree as the area it is planted in. That way, as the roots grow outward, they are still within a thriving environment.