Tree Oozing Sap From the Trunk in Richmond Hill?

You’re cutting the grass and you notice a wet, dark streak running down the trunk of the maple or the old elm out front. Maybe it smells a little sour. Maybe there’s amber gum on the cherry tree near the back gate. A tree weeping from its trunk catches your eye for good reason, and the cause ranges from harmless to serious.

What the Ooze Usually Is

Four things cause most trunk ooze in Richmond Hill yards. Look at the colour, smell the bark, and check for holes.

Slime Flux

Bacteria living inside the wood build up pressure and push a watery, foamy liquid out through cracks. It runs dark down the bark, often smells sour or like spoiled beer, and attracts flies and wasps in summer. Elms, maples, poplars and willows get it most. The old willows around Mill Pond show it often. It looks ugly, but a healthy tree can carry slime flux for years.

Gum on Cherries and Plums

Fruit trees in the Prunus family push out amber, jelly-like gum wherever they’re hurt. A mower nick, a frost crack, a borer hole or a canker can all set it off. A blob or two is the tree sealing a wound. Lots of gum spots up the trunk point to a stressed tree.

Resin on Evergreens

Spruces and pines bleed sticky resin wherever the bark is broken. If a spruce shows white, crusty resin low down and its bottom limbs are dying one after another, Cytospora canker is the usual culprit. The fungus works its way up the tree over several years.

Insects Under the Bark

Borers chew galleries just beneath the bark, and sap leaks where they enter and leave. Emerald ash borer marks its exits with tiny holes shaped like a capital D. On birch, bronze birch borer causes rusty stains and ridges in the bark, with the top of the tree dying first. Sap-loving insects also find any wet patch quickly, so check the area closely.

Reading the Rest of the Tree

The wet patch matters less than what the canopy and the base are doing. Take a few steps back and work through this list.

• Healthy crown, one weeping spot: usually a wound or a mild flux. Check it again next month.
• Holes near the ooze: insects are involved. On ash, that’s emerald ash borer until shown otherwise.
• Thin canopy or dead branches up top: the tree is struggling, and the ooze is one symptom of a bigger problem.
• Spongy wood or fungus growing near the root flare: rot is present, which affects how strong the trunk is.
• Bark peeling away around the weeping area: a canker may be killing that section of trunk.

Looking After a Weeping Tree

A flux or a healing wound needs very little from you, which is good news. Stop the mower and string trimmer from nicking the trunk by laying wood chips in a wide circle around it, kept a hand’s width off the bark. Water deeply during a dry August. Wash the bark with plain water if the smell bothers you.

Don’t drill holes to drain a flux, which is an old trick that spreads the problem. Don’t paint or tar the spot, and don’t cut out the weeping bark yourself.

Ash Trees Are the Exception

An ash that weeps from D-shaped holes, bark splitting or has woodpeckers flaking its bark off in pale patches almost certainly has emerald ash borer. Ash that dies this way dries out and turns brittle fast, which makes it dangerous to leave standing and harder to take down safely the longer it waits. Any treatment has to come from a licensed applicator, and it only helps while most of the canopy is still green. Our page on ash tree removal covers what happens once it’s too late.

Richmond Hill Rules to Know

Size decides the paperwork. Richmond Hill’s Tree Preservation By-law 19-25 took effect in April 2025, and it covers private trees whose trunks measure 15 cm or more at chest height. Those need a City permit before anyone takes them down. The process can differ for dead or hazardous trees, so ask the City. For a tree on the boulevard, call Access Richmond Hill at 905-771-8800 and let the City handle it.

Common Trees and What Their Ooze Means

Each species around Richmond Hill tends to weep for its own reasons, which narrows things down quickly.

• Silver and Norway maples: slime flux from old pruning cuts and frost cracks is common and slow-moving.
• Elms and poplars: wetwood flux, often with a strong smell in July and August.
• Cherries, plums and ornamental Prunus: amber gum at wounds, cankers or borer holes.
• Birch: rusty weeping with a dying top points to bronze birch borer.
• Ash: weeping with D-shaped holes means emerald ash borer.
• Blue spruce: white resin with lower limbs dying points to Cytospora canker.

Getting Scott to Look at It

Phone or text us at (289) 475-5822, any day between 8 in the morning and 8 at night. A picture of the weeping spot plus one of the whole tree helps, along with the species if you know it. Scott can usually visit that day, explain plainly what is going on, and price any work for free. When it turns out to be a harmless flux, he says so and you keep your money.