For a tree with 4 inches DBH, the critical root zone radius is how many feet?

For a tree with 4 inches DBH, the critical root zone radius is how many feet?

• A. 4 ft
• B. 6 ft
• C. 8 ft
• D. 10 ft

Answer: (B)

The critical root zone radius is estimated by a simple rule: multiply the diameter at breast height (in inches) by 1.5 to get the radius in feet. This reflects the idea that most of a tree’s important root area extends well beyond the trunk and needs protection during construction or soil disturbance. For a tree with 4 inches DBH, the calculation is 4 × 1.5 = 6 feet. So the critical root zone radius is 6 feet. This concept helps guide excavation, trenching, or root protection decisions to safeguard the tree’s stability and health.

The critical root zone radius is estimated by a simple rule: multiply the diameter at breast height (in inches) by 1.5 to get the radius in feet. This reflects the idea that most of a tree’s important root area extends well beyond the trunk and needs protection during construction or soil disturbance.

For a tree with 4 inches DBH, the calculation is 4 × 1.5 = 6 feet. So the critical root zone radius is 6 feet. This concept helps guide excavation, trenching, or root protection decisions to safeguard the tree’s stability and health.