Landscape beds, parking lots and construction activities around trees are all possible without harming the trees if you understand where the tree roots are and what they need to survive. The important feeder roots are located where soil space is available in the surface soil and radiate out in all directions far beyond the crown spread of the tree. To survive, roots need oxygen, adequate moisture and organic soil components. Fill dirt, soil compaction, soil contaminants, and damaging or cutting roots will kill trees.

Use the following guidelines to protect trees in potentially damaging situations.

LANDSCAPE BEDS

• Use a coarse organic soil mix when constructing beds around trees. Do not use any soil mix that has clay or silt in it.

• Do not till or dig up the existing soil around the tree.

• Only dig the holes necessary to install the landscape plants.

• Do not install plants within two feet of the trunk or root collar of the tree.

• Install irrigation in beds around trees very carefully. Do not cut through feeder roots to install irrigation pipes. Do not arrange sprinkle heads so that water hits the trunk of the tree.

• Select drought-tolerant plants for beds under trees. Some landscape plants require more water than most trees. Irrigate as little as possible.

• Check the irrigation system often and fix leaks immediately.

TREES IN PARKING LOTS

• Use tree species that are tolerant of heat and root restrictions. Consider the growth form of tree selections. Live oak and Chinese elm, both popular selections for parking lots, have low-spreading forms that require almost constant pruning. Some trees such as bald cypress have roots or “knees” that can be a problem in parking lots. 

• Root barriers or deflectors can be installed to prevent roots from up-lifting or otherwise damaging parking surfaces. 

• The critical soil space for a tree in a parking lot planting space is 100 square feet with a 5-foot minimum planting width. 

• On average, street trees and parking lot trees have a life span of approximately 12 years. In concrete or asphalt parking lots a minimum of 400 square feet (20 feet x 20 feet) planting area for each tree is necessary for healthier, more long-lived trees. 

• Porous parking lots made of gravel, limestone or grass pavers are much better for trees since the roots can survive under the parking lot and are not as restricted by the size of the planting space.

TREES AND CONSTRUCTION

• The first thing that should be done to protect trees in a construction area is to communicate with the construction crew and educate them about protecting the trees from construction activities.
  
  
• Protect the critical root zone with a fence completely around the tree. The critical root zone is equal to the crown spread of the tree at minimum. A fence is more substantial and works a lot better than flagging. Monitor the fence often to make sure everyone understands to leave this area alone.
  
  
• Before constructions begins, treat the critical root zone area by aerating the soil, applying a root stimulator and mulching. This should be done before construction and a year later after construction.
  
  
• Following are things not to do in the critical root zone:
  
  
• Do not trench for electrical, water, sewer, gas or for any other reason.
• Do not grade, fill or otherwise disturb the soil.
• Do not park vehicles or heavy equipment or store materials.
• Do not dump concrete slag, drywall, paint or any other material.
• Do not attach signs or otherwise damage the trunk or branches.
• Do not allow anyone except an arborist to prune the tree for any reason.
• Do not take down the fence until all construction is finished.