Caring for Aging Maple Trees: Addressing Bark Loss, Mushrooms, and Lichens

Understanding the Symptoms

You have three maple trees over 60 years old. One has lost a significant portion of its lower bark, more is chipping off, mushrooms are growing at the base, and a light green fungus (lichens) appears on the trunk. The tree still has leaf buds, but you're concerned about its health and stability near your house.

Are Mushrooms a Threat?

Mushrooms growing on the ground around the tree—or even from the trunk—are not a direct problem. They indicate the tree is likely hollow, which does not affect overall health but may weaken the tree against wind breakage. The green growth is lichens, a harmless symbiotic organism that does not harm the tree.

Practical Care for Declining Urban Maples

Watering

Thoroughly water every week or two during extended dry weather. Use a slow stream from a hose, moving it periodically to soak the entire soil area under the tree's branches to a depth of six or more inches.

Fertilizing

Apply a complete fertilizer (13-13-13) in spring and/or late fall. The general rate is 2 to 4 lbs per inch of tree diameter (0.35 to 0.7 kg per cm at 1.5 m above ground). Broadcast over the ground surface; higher rates may risk burn on nearby turf.

Pruning

Prune dead branches to stimulate vigorous shoot growth. Best done in early spring before budbreak to promote healing of cuts.

Reducing Salt Runoff

Minimize salt-laden spring water runoff over the roots, which can contribute to decline.