Spots can look alike and have quite different causes. The shape, colour and feel of the spot tell you most of what you need.
How to tell them apart
- Dry, pale or papery patches on the side facing the window. Sunburn. Direct sun through glass can scorch leaves.
- Round or irregular spots, often with a yellow ring, that spread and look wet or dark. A fungal or bacterial leaf spot. These like leaves that stay wet.
- Tiny dots, webbing or stippling underneath the leaf. Spider mites or other small pests.
- Raised brown bumps that scrape off with a fingernail. Scale insects.
- Brown, mushy patches near the base or on stems. Often rot from too much water.
What to do
- Move the plant out of harsh direct sun if the spots are dry and papery.
- Remove badly affected leaves with clean scissors. Throw them away; don't compost them.
- Water the soil, not the leaves, and water in the morning so leaves dry quickly.
- Give the plant room and some gentle air movement so leaves don't stay damp.
- Check the undersides of leaves for pests. Wipe them with a damp cloth or a mild soapy solution.
- Keep the plant apart from others until you know the cause.
When to scan
A fungal spot spreads. If new spots keep appearing after a week, take a close-up photo of one spot and a photo of the whole plant in daylight, and scan them. The more clearly the spot shows, the better the answer.