Dark liquid is oozing from my tree's bark. Is my tree dying?

Dark liquid oozing from bark — called slime flux or bacterial wetwood — is a common condition caused by bacteria fermenting sap inside the tree. While it looks alarming, it's important to understand the difference between wetwood and more serious oozing.

Bacterial wetwood / slime flux:

• Foul-smelling, dark liquid seeps from wounds, cracks, or branch crotches
• Often leaves a grey-white streak down the bark as it dries
• Common in elms, maples, oaks, poplars, and willows
• Caused by several anaerobic bacteria that ferment sap, creating gas pressure inside the trunk
• Generally NOT fatal — many trees live for decades with wetwood

More concerning types of oozing:

• Clear, sweet-smelling sap from oaks in spring/summer could indicate oak wilt (see our Oak Wilt Guide)
• Reddish-brown ooze from cankers on fruit trees may indicate bacterial canker or Phytophthora
• Frothy ooze with sawdust near the base could signal boring insect activity

What to do:

1. Do NOT drill holes to relieve pressure — this outdated practice causes more harm than good.
2. Avoid inserting drain tubes — another outdated recommendation.
3. Keep the tree healthy with proper watering, mulching, and avoiding unnecessary wounds.
4. Have an arborist inspect to rule out structural weakness in the oozing area.
5. If oozing is associated with a deep crack or cavity, a risk assessment may be warranted.

Read more about bark concerns in our Tree Bark Peeling Guide and learn how to assess tree health in Signs Your Tree Is Dying.