Ash Tree Green Trunk Coating: Lichen Identification and Tree Health

Two ash trees; one puny with dead branches, sparse canopy. Main trunk covered in green moldy substance.

Diagnosis: Lichen (Not Mold)

Symbiotic algae+fungi. Three forms: crustose (flat), foliose (leafy), fruticose (bushy). Common in high humidity. Epiphytes — get nutrients from air, not tree.

Impact and Management

• Slightly detrimental — mainly indicates thin canopy (more light = more lichen).
• Not the cause of decline — effect of poor health.
• Best control: Improve tree vigor → dense canopy shades limbs → reduces lichen photosynthesis.

Action

Fertilize with 10-10-10 at 1 lb per inch trunk diameter, watered in. Improves health, thickens canopy. Baking soda treatment (0.4 lb/gal) mentioned but not recommended — address root cause (vigor) instead.