Crowded Parchment Fungus Is Peaking This October — Here's What Homeowners Need to Know

If you've been noticing unusual fungal growth on trees or woody debris in your yard, October may be exactly the reason why. Crowded parchment (Stereum complicatum and related species), a moderate-severity wood-decay fungus, is entering peak activity this month — and homeowners across nearly 20 states should be paying attention.

Check our seasonal forecast for a full picture of what's active in your region right now, or jump straight to the full details on crowded parchment.

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Why October Matters for This Threat

Crowded parchment follows a broad seasonal pattern. Based on typical activity timing, this fungus tends to be present and active from late winter through early summer, then resurges again in the fall — with September, October, and November representing a significant second wave of activity.

October is particularly notable because conditions often align in its favor: temperatures cool, rainfall increases in many regions, fallen leaves accumulate, and tree canopies thin out as deciduous trees head into dormancy. Decaying wood and leaf litter create ideal substrate for fungal colonization, and the slower growth pace of trees means they have less energy available to compartmentalize damage.

In short, fall is prime time for wood-decay fungi like crowded parchment to establish and spread — and October sits right at the center of that window.

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What to Look for Right Now

Crowded parchment typically appears as thin, leathery, shelf-like or crust-forming fungal bodies growing on the surface of wood. These fruiting bodies often emerge in dense, overlapping clusters — hence the "crowded" name — and may display tan, orange-brown, or grayish tones with a parchment-like texture on their upper surface.

Look for it on: - Dead or dying branches still attached to the tree - Recently cut stumps or exposed wound wood - Fallen logs and woody debris on the ground - The base of trees where bark may be compromised

Because this fungus is classified as a wood-decay organism, its presence on a living tree is a signal worth investigating — even if the fruiting bodies themselves appear on dead wood nearby. The fungus may be working beneath the bark on compromised tissue before becoming visible.

Not sure what you're looking at? Use our diagnosis tool to help identify what's growing on your trees.

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Where It's Active

Crowded parchment has been documented as currently active across a wide swath of the eastern United States, including:

Ohio, New York, Delaware, Alabama, Pennsylvania, North Carolina, Georgia, Maryland, Massachusetts, New Jersey, Michigan, Tennessee, Illinois, Kentucky, Indiana, Minnesota, Connecticut, Florida, and Virginia.

If you live in any of these states, now is a good time to do a walk-through of your property with fresh eyes.

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What to Do This Month

The good news: there are concrete steps you can take in October to reduce risk and limit the spread of crowded parchment on your property.

1. Sanitation and Pruning Remove and properly dispose of any infected branches, woody debris, and fallen material. Don't leave it piled near healthy trees. Improving air circulation by thinning dense areas of the canopy can also reduce the moist, stagnant conditions fungi prefer. Always sterilize your pruning tools between cuts — a diluted bleach solution or isopropyl alcohol works well — to avoid accidentally spreading fungal material from one branch or tree to another.

2. Soil and Moisture Management Fall rains can create persistently wet soil conditions that favor fungal pathogens. Make sure your trees have adequate drainage, and avoid overwatering if you're still irrigating. Applying a 2–4 inch layer of mulch around the base of trees (keeping it away from direct contact with the trunk) can help regulate soil moisture and reduce splash dispersal of spores.

3. Fungicide Application (Where Appropriate) If infection is confirmed or strongly suspected on a living tree, systemic or contact fungicides can be part of a management plan. Apply at the first clear sign of infection, and be prepared for repeat applications during wet stretches of weather. Always follow the product label for rates and timing. Note that fungicides are most effective as a preventive or early-intervention measure — not after extensive decay has set in.

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When to Call an Arborist

Not every fungal fruiting body signals a crisis, but some situations genuinely call for a professional assessment. Consider reaching out to a certified arborist if:

• Fungal growth is appearing on the main trunk or major structural limbs of a tree
• You notice soft, spongy, or discolored wood beneath the bark near the fruiting bodies
• A tree shows signs of structural decline — leaning, dieback, or significant branch loss
• You're unsure whether what you're seeing is crowded parchment or something else entirely

An ISA Certified Arborist can evaluate whether the decay poses a safety risk, recommend a treatment plan, or advise on removal if necessary. Find a qualified arborist near you to get an expert set of eyes on your trees before winter arrives.

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October is a short window, but it's an important one. A little attention now — clearing debris, improving drainage, and knowing what to watch for — can make a real difference in the health of your trees heading into the dormant season and beyond.