What causes brown spots on plant leaves?
Where the spot sits on the leaf, and whether it has a defined edge, tells you which of three very different problems you have.
The causes, and how to tell them apart
Root rot showing in the leaves most common on figs
How to tell: Dark brown or near-black spots starting at the leaf CENTER or at the base near the stem, sometimes with a yellow halo, spreading outward. Soil stays wet.
What to do: This is a root problem showing up in the leaves. Let the soil dry, check the roots, and repot into fresh fast-draining mix if any are soft or brown.
Underwatering or sun scorch common
How to tell: Dry, tan or light-brown, crispy patches at the leaf EDGES and tips, often on the side facing the window.
What to do: Water more consistently, and move the plant back from glass that gets direct afternoon sun. Scorched tissue will not recover.
Bacterial or fungal leaf spot less common
How to tell: Spots with a distinct dark border, sometimes a yellow ring, that multiply and spread to neighbouring leaves. Often follows water sitting on foliage.
What to do: Remove affected leaves, improve airflow, stop misting, and water the soil rather than the leaves.
Physical damage common and harmless
How to tell: A single mark with a torn or irregular edge that never grows or spreads. New leaves are clean.
What to do: Nothing — a knock, a pet, or a tear during shipping. Not an infection.
The species most prone to scorch and to wet-leaf spotting
Sun scorch and fungal leaf spot are two of the causes above, and both are far likelier on some plants than others — the ones that take no direct sun, or that resent water sitting on their leaves and crowns.
| Species | Direct sun | Heat damage above |
|---|---|---|
| Calathea | no direct sun at all — it bleaches and crisps | 90°F |
| Boston fern | no direct sun | 90°F |
| Heartleaf philodendron | no direct sun | 95°F |
| Aglaonema | no direct sun — the painted/pink cultivars want more light than the dark green ones | 95°F |
| Corn plant | no direct sun — bleaches the foliage | 95°F |
| Madagascar dragon tree | tolerates some morning sun | 95°F |
| Peace lily | no direct sun | 95°F |
| Anthurium | no direct sun | 95°F |
| String of pearls | morning sun ideal; scorches in hot afternoon sun | 95°F |
| Parlor palm | no direct sun | 95°F |
Scorch appears only on the leaves that face the light source and does not spread. A leaf spot infection spreads, and usually has a yellow halo.
By species
The likely answer differs by plant — these species have their own version of this problem:
Plantroster compares this month's photo against last month's, so slow changes — the ones you stop noticing because you see the plant every day — get flagged.
Open PlantrosterOther problems
General horticultural guidance, not a diagnosis of your specific plant.