Pocket Botanist
Check these first
- Check if the spots are powdery or flat.
- Inspect the underside of the leaves.
- Check for poor air circulation around the tree.
Likely causes
Oak mildew
Most likelyHow to tell: White, powdery patches appear on the leaves. This often happens in humid or stagnant air conditions.
What to do: Prune branches to improve airflow through the canopy. Use a fungicide spray if the infection is widespread.
Leaf spot fungi
PossibleHow to tell: Dark brown or black spots with yellow halos. These spots often appear after long periods of wet weather.
What to do: Rake up and dispose of fallen leaves to prevent spores from overwintering. Keep the area around the tree clean.
Find out what's wrong with your sessile oak
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.
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When to worry
Mildew is common in late summer and rarely kills the tree. Worry if the spots cause premature leaf drop across most of the tree.
Stopping it coming back
Water at the base of the tree rather than overhead to keep leaves dry. Thin out branches to allow light and air to reach the center.
Sessile oak: spots? Check yours with a photo
Every plant is a little different. Take a photo of your sessile oak 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
- Will mildew kill my oak?
- It is unlikely to kill a healthy, established oak. It is mostly a cosmetic issue that can stress the tree if it happens every year.
- Can I compost the spotted leaves?
- No, it is best to burn or dispose of them in the trash to avoid spreading fungal spores back into your garden.
Guides to these causes
More problems with Sessile oak
- What are these pests on my Sessile oak?
- Why are my sessile oak leaves curling?
- Why are my Sessile oak leaves turning yellow?
- Why are my sessile oak leaf tips turning brown?
- Why is my sessile oak drooping?
- Why is my Sessile oak losing its leaves?
- How do I know if my Sessile oak has root rot?
- Why is my Sessile oak growing so thin and leggy?
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.