What Are the Brown Spots on My Plant’s Leaves?
Brown spots on leaves can come from fungal or bacterial leaf spot disease, but also from sunburn, overwatering, or minerals. Here is how to identify the cause and stop the spots from spreading.
Brown spots are one of the trickier symptoms to diagnose because several very different problems produce them. True leaf spot disease, caused by fungi or bacteria, is the classic culprit and tends to spread, but identical-looking spots can come from sun scorch, overwatering, cold damage, or water-quality issues. Reading the appearance and pattern of the spots is the key to telling them apart.
Disease-related spots usually start small and circular, often with a yellow halo or a darker ring, and they multiply and merge over time, frequently appearing after the leaves have been wet. Spots from sunburn sit on the most sun-exposed leaves, while overwatering tends to cause soft brown patches and yellowing. Pinning down which one you have determines whether you reach for a fungicide or simply change your care.
Signs to look for
- Small round brown or black spots, often ringed with a yellow halo, that multiply over time
- Spots with concentric rings or a darker margin (typical of fungal leaf spot)
- Water-soaked, mushy, or translucent-edged spots (a sign of bacterial infection)
- Spots that appear or spread after leaves have stayed wet or humidity has been high
- Dry, crispy brown patches on sun-exposed leaves (scorch rather than disease)
What causes it
Fungal leaf spot
The most common disease cause. Fungi produce circular brown spots, often with concentric rings or a yellow halo, that enlarge and spread, especially when leaves stay wet and air is stagnant.
Bacterial leaf spot
Bacteria cause water-soaked spots that may look greasy or translucent at the edges and sometimes have a yellow halo. They spread fast in warm, wet conditions and on splashed water.
Sunburn or scorch
Direct sun bleaches and burns exposed leaves into dry brown patches. Unlike disease, these stay put, do not spread, and appear only on the sun-facing leaves.
Overwatering and root stress
Soggy roots can cause brown, often soft or yellow-ringed spots and blotches as the plant struggles to manage water, frequently alongside general yellowing and wilting.
Water quality and minerals
Fluoride, chlorine, and salt buildup from tap water can cause brown spotting and tip burn in sensitive plants like dracaenas, calatheas, and spider plants.
How to fix it
- 1Isolate the plant and remove affected leaves
If you suspect disease, move the plant away from others to prevent spread, and prune off spotted leaves with clean scissors, sterilizing the blades with alcohol between cuts. Discard the leaves rather than composting them.
- 2Stop wetting the foliage and improve airflow
Water only at the soil line, keep leaves dry, and increase air circulation with spacing or a small fan. Fungal and bacterial spots thrive on wet leaves and stagnant air, so dry foliage is critical.
- 3Apply a fungicide for confirmed fungal spot
For spreading fungal leaf spot, treat with a copper-based fungicide or a neem oil spray according to the label, repeating as directed. Bacterial spots do not respond to fungicide, so for those focus on removing infected leaves and keeping foliage dry.
- 4Rule out and correct sun or water issues
If the spots are dry scorch on sun-exposed leaves, move the plant out of direct sun. If they trace to overwatering, let the soil dry appropriately and check roots. For mineral spotting, switch to filtered or distilled water and flush the soil.
- 5Adjust watering and environment
Let the top inch of soil dry between waterings for most plants, ensure the pot drains freely, and avoid the cold drafts and high stagnant humidity that stress leaves and favor disease.
- 6Monitor new growth
Watch the plant over the next few weeks. If no new spots appear on fresh leaves, the problem is controlled. Existing spotted leaves will not heal, but you can remove the worst of them once the plant has recovered enough.
How to prevent it
- Water at the soil line and keep foliage dry, especially overnight
- Give plants good spacing and air circulation to discourage fungal growth
- Avoid overwatering and ensure every pot drains freely
- Use filtered or distilled water for plants sensitive to fluoride and salts
- Inspect new plants and isolate any showing spots before grouping them with others
FAQ
How can I tell if brown spots are a disease or just sun or water damage?
Disease spots are usually small, round, often ringed with a yellow halo or concentric rings, and they multiply and spread, especially after leaves get wet. Sunburn spots are dry patches only on sun-facing leaves and do not spread, while overwatering causes soft brown blotches with general yellowing.
Should I cut off leaves with brown spots?
Yes, if you suspect fungal or bacterial leaf spot, remove affected leaves with sterilized scissors to slow the spread and discard them. For a leaf with just a small cosmetic spot from sun or minerals, you can leave it or trim the damaged area, since it will not spread.
Are brown spots contagious to my other plants?
Fungal and bacterial leaf spots can spread to nearby plants through splashed water and contact, so isolate an infected plant and keep foliage dry. Spots caused by sunburn, overwatering, or hard water are not contagious and only reflect that individual plant's conditions.