Why have the leaves on my plum tree gone silver?

The test that separates real silver leaf from harmless false silvering, how far the infection has usually travelled by the time you see it, and when a tree is worth saving.

Difficulty: intermediate
Time: 45 min
Read: 5 min
Safety: caution

Short answer

Cut through an affected branch. Real silver leaf leaves a distinct dark brown or purple stain in the centre of the cut wood; false silver leaf leaves the wood clean. If the wood is stained, cut that branch out in summer, at least 15cm below any staining, and destroy the wood. If the trunk is stained or brackets have appeared, the tree cannot be saved.

Silver leaf is a wood-rotting fungus that enters through wounds, grows inside the branches and produces a toxin that separates the layers of the leaf, giving a metallic sheen. By the time a branch silvers, the fungus is already well established in the wood behind it. What decides the outcome is how far it has travelled: a single branch is often removable, a stained trunk is not.

Safety

A tree killed by silver leaf decays from the inside and can shed limbs without warning. Once brackets appear on the trunk, the structure is compromised — do not climb it or work under it, and have anything overhanging a path, road or building assessed by an arborist.

What you'll need

Pruning saw and secateurs
Disinfectant for tools
Bags for infected wood

Step by step

Look at how the silvering is distributed.Silver leaf typically starts on one branch or one part of the tree and spreads to others over seasons. Silvering that appears evenly all over the tree at once is more likely to be false silver leaf.
Do the cut test — this is the diagnosis.Saw through an affected branch at least 2–3cm thick. Real silver leaf shows a dark brown or purplish stain in the heartwood at the centre of the cut. False silver leaf shows clean wood. Nothing else is conclusive.
If the wood is clean, do nothing much.False silver leaf is a stress response to drought, cold or poor nutrition. Water, mulch, feed in late winter and it usually recovers over a season or two.
If the wood is stained, cut the branch out — in summer.Cut back at least 15cm beyond the last visible staining, into clean wood, and check the cut face again. If the stain continues, keep going. Stone fruit is only cut between late spring and midsummer.
Destroy the infected wood.Off site or burned where permitted. Do not stack it as logs or leave it in a heap — the fungus fruits on dead wood and releases spores, mainly in autumn and winter.
Disinfect the saw and secateurs afterwards.Before touching another plum, cherry or apple. Blades carry the infection efficiently.
Check the trunk and main limbs.Staining that reaches the trunk means the fungus is in the main structure. That tree will die, usually over two to four years, and the sensible decision is to plan its replacement.
Look for the fruiting bodies.Small overlapping brackets, purplish underneath, on dead wood. Their appearance means the wood behind them is dead and the tree is in the final stage. Remove that wood promptly to protect other trees nearby.
Reduce the wounds it enters through.Prune stone fruit only between May and July, on a dry day, cut cleanly to the collar, deal with storm damage immediately rather than leaving a torn wound over winter, and thin heavy crops so branches do not break.

Tips

Silver leaf also affects apples, pears, roses and other woody plants, though plums and cherries are by far the most susceptible.
The fungus is common in the environment on dead wood, so a nearby dead tree, an old log pile or a neglected plum in a neighbouring garden is a permanent source. You are managing exposure, not eliminating it.
Do not replant a plum on the same spot after a tree killed by silver leaf — plant elsewhere, or plant something unrelated.
A tree with silver leaf on one branch can carry on cropping normally for many years if that branch is removed promptly and the tree is otherwise healthy.

Common mistakes

Diagnosing silver leaf from the leaves alone — False silver leaf looks the same on the foliage and is not a disease at all. Cutting a branch and looking at the wood is the only reliable test, and it takes two minutes.
Cutting out infected wood in winter — Winter is when the spores are most abundant and the tree seals wounds worst. Cutting out silver leaf in January risks infecting the tree in a new place while removing it from an old one.
Keeping the infected wood as logs — The fungus fruits on cut dead wood and produces the spores that infect the next tree. Get it off the site.
Cutting only to the edge of the visible stain — The fungus extends beyond what shows. Cut at least 15cm past the staining and check the new cut face.

If it doesn't work

Silvered leaves on one branch, dark stain in the cut wood

Cause: Silver leaf, localised — Fix: Remove the branch in summer, cutting well below the staining, and destroy the wood. The tree often carries on cropping.

Silvered leaves all over, clean wood when cut

Cause: False silver leaf — drought, cold or nutrient stress — Fix: Water deeply, mulch, feed with potash in late winter. It recovers over a season or two.

Staining visible in the trunk

Cause: Silver leaf established in the main structure — Fix: No cure. Plan replacement, keep the tree only while it is structurally safe, and remove it before it becomes a hazard.

Purple-brown brackets on the bark

Cause: Fruiting bodies on dead wood — Fix: The wood behind them is dead. Remove and destroy it promptly to protect other stone fruit nearby.

Questions people ask

How do I know if it is really silver leaf?

Cut through an affected branch of a few centimetres thickness. A dark brown or purple stain in the centre of the cut wood confirms it. Clean wood means false silver leaf, which is a stress response and not the disease.

Can silver leaf be cured?

There is no chemical cure. Removing infected branches well below the staining, in summer, stops it in many trees. Once it reaches the trunk, it cannot be stopped.

Is fruit from a tree with silver leaf safe to eat?

Yes. The disease is in the wood, not the fruit. Fruit from affected branches may be smaller or fail to ripen as the branch dies back.

Can I plant another plum where one died of silver leaf?

Better not to. Any remaining infected root or stump material is a spore source. Plant elsewhere in the garden, or plant something other than stone fruit in that spot.