Fruitless Mulberry with Mushrooms, Sap Leakage, and Trunk Cracks: Slime Flux Explained

Recognizing Slime Flux (Wetwood)

Mushrooms at the base, sticky sap oozing from trunk cracks, and fissures 4–6 inches long on a 20-year-old fruitless mulberry in Oakley, CA, are classic signs of slime flux (wetwood)—a bacterial condition common in mulberry, elm, maple, oak, and willow.

What's Happening Inside

Fermenting bacteria produce gas pressure within the wood, forcing sap through cracks, wounds, and branch unions. The flux darkens on air exposure, smells foul or alcoholic, and attracts insects. Though unsightly, it's rarely fatal to otherwise healthy trees.

Management—No Cure Needed

• Do not drill drain holes—they spread infection.
• Remove loose/dead bark in affected areas to promote drying.
• Maintain vigor: water during heat/drought, fertilize annually.
• Minimize wounds (mowers, trimmers, improper pruning).

Fluxing often stops spontaneously. The mushrooms are secondary decomposers on dead bark, not the primary cause. Your trees' overall beauty suggests they're coping well.