Pocket Botanist
Check these first
- Examine the branches for sunken, dark lesions.
- Check if the spots are only on the leaves or on the wood.
- Look for oozing sap near the spots.
Likely causes
Black canker
Most likelyHow to tell: You will see dark, sunken lesions on the branches that may eventually girdle the limb. The leaves above the spot might wilt or die.
What to do: Prune out the infected branches at least 6 inches below the visible lesion. Sterilize your shears with rubbing alcohol between every cut to prevent spreading the fungus.
Leaf spot fungi
PossibleHow to tell: Small brown or black spots appear on the leaves, sometimes with a yellow halo. This usually happens during very wet, humid weather.
What to do: Rake up and dispose of all fallen leaves to reduce fungal spores in the area. Ensure the tree has good air circulation by thinning out crowded branches.
Find out what's wrong with your black willow
The list above covers the usual causes. Pocket Botanist looks at a photo of your actual plant and tells you the likely cause, how serious it is, and what to try first. Identification and a health check are free.
Scan with your phone's camera to get the app
Or go to pocketbotanist.app/get on your phone
When to worry
Worry if the cankers are on the main trunk, as this can be fatal to the tree. Leaf spots are mostly cosmetic and rarely kill a mature willow.
Stopping it coming back
Avoid overhead watering that keeps the foliage wet for long periods. Prune in late winter to improve airflow through the canopy.
Black willow: spots? Check yours with a photo
Every plant is a little different. Take a photo of your black willow and Pocket Botanist tells you which cause is most likely, how serious it is, and what to try first. A few checks a day are free. Save the plant and you get care reminders timed for it.
Scan with your phone's camera to get the app
Or go to pocketbotanist.app/get on your phone
Get the app · Or check it from a photo now, free
Questions people ask
- Is black canker contagious?
- Yes, it spreads through spores in wind and rain. Always clean your tools after pruning infected wood.
- Should I paint the pruning wounds?
- No, it is better to let the tree heal naturally. Painting can trap moisture and encourage more rot.
Guides to these causes
More problems with Black willow
Back to the Black willow guide
This article was generated with AI on from the plant’s care profile and is general information, not horticultural advice. Read about how we build these guides.