Slime Flux on Maple: Understanding the Smelly Sap Condition

What Is Slime Flux?

A homeowner reports dead branches and foul-smelling sap oozing from a Kingston hardwood maple. The expert identifies this as slime flux (also called wet wood), a condition caused by bacterial fermentation inside the tree.

How It Develops

Bacteria enter through wounds—from construction, mowing, or storm damage—and colonize the heartwood. Their metabolic activity produces methane gas, building pressure that forces dark, frothy, odorous liquid out through bark cracks. The liquid darkens on exposure to air and may attract insects.

Is It Fatal?

Slime flux itself does not kill the tree. It indicates past injury, and the tree’s survival depends on the extent of that injury and overall stress. Long-term flux can discolor bark and kill nearby grass or moss.

Management Tips

• Reduce stress: water during drought, avoid further wounds.
• Fertilize with 10-10-10 at 1 lb per inch of trunk diameter, watered in well.
• If odor or insects are problematic, flush the area with water or a diluted bleach solution.
• Do not install drain tubes—they can spread bacteria and invite decay fungi.

A Mixed Blessing

Interestingly, the wet wood condition creates an internal environment hostile to wood-decay fungi, offering some protection against more serious rot.