What is a key guideline for mulch around trees to prevent moisture-related disease?

• A. Apply a thick layer directly against the trunk.
• B. Water frequently on the trunk.
• C. Keep mulch away from base of tree stems to prevent moisture accumulation and disease.
• D. Paint the trunk with mulch.

Answer: (C)

Moisture around the trunk is the enemy, so mulch should never be piled against the base of the tree. When mulch sits against the bark, it traps dampness and warmth, creating a perfect spot for fungal diseases and bark decay at the collar. Keeping a gap between the mulch edge and the trunk (a few inches, with a 2–4 inch mulch depth) allows air to circulate and the trunk to dry after rain, which greatly reduces disease risk. Water should go into the soil, not onto the trunk, and there’s no benefit to painting or applying mulch directly to the trunk. That’s why keeping mulch away from the base is the best guideline.