Why is sap leaking from my tree?
Wet, dark streaks running down the bark, sticky or foamy ooze from a crack or old wound, or clear sap dripping steadily from a cut.
Watch it, correct the care behind it, and check again next season. Nothing here threatens people or property in its current state.
Most trunk ooze in Kansas is bacterial wetwood — unsightly, chronic, and rarely what kills a tree. Two versions deserve more attention: dark, tarry bleeding low on the trunk or at the root flare, which can indicate a root-collar disease, and sap that comes with sawdust, which means something is tunneling in there.
What this looks like
Follow the streak upward to its source, because the source is the whole diagnosis. Wetwood emerges from a crack, an old branch stub, or a wound, smells sour and fermented, and dries to a pale gray-white crust that kills the grass beneath. Alcoholic flux foams at the base like beer and is short-lived. Borer sap comes with sawdust at a small, specific hole. And a dark, tarry stain seeping at ground level, with dead bark under it, is the one that points at the root collar.
- A vertical wet streak that runs for weeks and stains the bark gray-white as it dries
- A sour, fermented smell at close range
- Foam or froth at the base of the trunk in hot weather
- Sap mixed with sawdust or gritty frass at a discrete hole
What causes it in Kansas
Roughly in order of how often each turns out to be the answer here. The line under each one is what separates it from the others — open a cause for the detail.
1Bacterial wetwood and slime flux
How to tell: Long-running wet streaks from a crack or old stub, a sour smell, and a gray-white crust below.Bacteria colonize the wet interior wood, gas pressure builds, and sap is forced out through any opening. Elm, cottonwood, mulberry, maple, and poplar are the Kansas regulars. It is chronic, it is nearly impossible to eliminate, and mature trees carry it for decades.
2Spring bleeding from cuts
How to tell: Clear, thin, odorless liquid from a fresh pruning cut, before the tree has leafed out.Maple, birch, walnut, elm, and grape push sap under root pressure in late winter. A cut made in February or March can run for weeks. It looks alarming and costs the tree essentially nothing.
3Alcoholic or frothy flux
How to tell: Foamy rather than merely wet, low on the trunk, gone in a week or two.Yeasts ferment sap in the outer wood of drought-stressed trees, producing a white foam with a distinctly beery smell at the base. It typically appears in hot weather and stops on its own.
4Borer activity
How to tell: Sap issuing from a small, discrete hole, with sawdust in it, rather than from a crack or wound.Clearwing borers and bark beetles push a mixture of sap and frass out of their tunnels. On pines, bark beetle attacks produce pitch tubes — dime-sized blobs of resin on the trunk.
5Phytophthora bleeding canker
How to tell: Dark, tarry, ink-like staining at or near ground level, with dead, sunken bark beneath it and often a thinning crown.A soil-borne pathogen that kills tissue at the root collar and the base of the trunk. It favors poor drainage, deep planting, and mulch piled against the bark, all common in Kansas landscapes.
6Canker fungi with resin flow
How to tell: Hardened white or amber resin at branch collars on a conifer, with browning branches above.On spruce and pine, Cytospora and related cankers produce white to amber pitch masses where branches meet the trunk, usually working from the lower branches upward.
What to do, and what to avoid
Safe to check yourself
All from the ground — no ladder, no saw.
- Trace the streak back to its origin — crack, wound, discrete hole, or ground level
- Smell it from a foot away: sour and fermented is wetwood, and that is reassuring
- Pull back the mulch and look at the root flare for dark staining or sunken bark
- Check whether the crown above the affected side is thinning
What not to do
The responses that make this one worse or permanent.
- Do not drill drainage holes or install tubes; this was standard practice decades ago, it does not relieve the condition, and it creates new wounds
- Do not seal, paint, or wrap the area
- Do not cut away bark to 'let it dry out', which enlarges the injury
- Do not pile mulch against the trunk, which is a direct contributor to root-collar disease
When to contact an arborist
Whatever this narrows it down to, the assessment that decides what happens next has to happen at the tree. Why that is
Common questions
Can wetwood be cured?
Can wetwood be cured?
No, and it rarely needs to be. The practical response is to keep the tree in good condition, accept the staining, and avoid wounding the trunk further. Grass under a chronic seep will not grow, which is usually the real complaint.
My maple bled for weeks after I pruned it in March. Did I hurt it?
My maple bled for weeks after I pruned it in March. Did I hurt it?
No. Late-winter bleeding in maple, birch, and walnut is water under root pressure and stops once leaves emerge and the tree starts transpiring. Prune those species in summer or late fall if the appearance bothers you.
Is the ooze attracting insects?
Is the ooze attracting insects?
Wasps, flies, and beetles will feed at a seep, and they are consuming the fermented sap rather than damaging the tree. Their presence is not a sign that the situation is getting worse.
Kansas Tree Guide is an independent educational resource. Nothing on this site replaces an on-site assessment by a qualified arborist or tree-care professional. Last reviewed August 2026.
Often seen alongside this
A second symptom narrows the cause faster than more detail about the first.
Not what you are seeing? Work the symptom guide again.