Green "Moss" on Japanese Maple Branches: It’s Lichen, Not a Problem

Identification

The thick green coating on your 5-year-old Japanese maple’s bare branches is lichen—a symbiotic fungus/alga, not moss or mold.

Why It’s Harmless

• Lichens are epiphytes: they manufacture their own food via photosynthesis.
• They don’t penetrate bark or extract nutrients from the tree.
• They thrive on sun-exposed branches—often appearing after canopy thinning or leaf drop.

No Treatment Needed

Lichens indicate good air quality and do not cause decline. They’re simply more visible on stressed trees with open canopies. Improving tree vigor (water, mulch, appropriate fertilizer) will thicken the canopy and naturally reduce lichen colonization.

If You Insist on Removal

Copper fungicides (labeled for ball moss) or baking soda sprays can suppress lichens, but they’re unnecessary and may harm beneficial organisms. Best advice: leave them alone.