Carrotwood Tree Leaf Drop: Too Much Water Can Be Just as Harmful as Too Little

A 20-year-old carrotwood tree in Southern California began thinning dramatically after a sprinkler malfunction soaked its trunk, leading to green moss growth four feet up. The owner corrected the irrigation, but leaf drop continued. Nearby carrotwoods remained healthy.

Diagnosis: Waterlogged Roots and Anaerobic Soil

Steve explains that saturated soil displaces oxygen, creating anaerobic conditions that suffocate roots and invite root diseases. Clay soils exacerbate the problem. The "moss" is likely algae thriving on constant moisture—a symptom, not the primary cause.

Prognosis and Care

• Time is the best remedy. The tree is well-established, which favors recovery.
• Leaf drop may be temporary; a new flush often follows once roots recover.
• Do not apply wound dressings or fertilizers now; they can add stress.
• Ensure the sprinkler issue is fully resolved and monitor soil drainage.

Protect the bark from mechanical damage (mowers, trimmers), as wounds compound stress. With patience, the tree should rebound.