Wood Decay

Look for moist, soft, or spongy wood that's lighter in color than healthy wood, sometimes with fine black lines running through it. On birches and maples in Western Washington, you'll spot woody, hoof-shaped conks (fruiting bodies) growing from trunks or branches; they may have a smooth gray surface or become rough and cracked with age. These fungal structures signal that decay has been progressing inside for months or even years. The damage is often hidden until a branch suddenly fails or the tree shows obvious signs of weakness.

Wood decay fungi enter through wounds: pruning cuts, storm damage, sunburn cracks, or mowing injuries. Once inside, they spread slowly through heartwood and sapwood, weakening the structural integrity of branches and trunks. The key to managing this is prevention: avoid large wounds, make clean pruning cuts near the branch collar, prune when branches are small, keep mower equipment away from the trunk, and don't overhead-irrigate onto the bark. If you see conks or suspect decay, inspect the tree with an arborist to assess stability and avoid property damage.