Most likely cause
Underwatering and low humidity are the top reasons a Calathea curls. The leaf rolls inward as a protective response to conserve the water it has left. You can confirm this in seconds.
Press a finger into the soil. If the top inch is dry, the pot feels light, and leaf edges are crisping or browning, the plant is dehydrated. Curling that worsens during dry afternoons or near heaters points the same way. Calatheas are native to humid tropical floors and react fast when the air gets dry.
Other causes
If the soil is moist and humidity is fine, work down this ranked list.
- Low humidity: Edges curl and brown evenly across many leaves. Confirm with a cheap hygrometer reading below 40 percent.
- Too much direct light or heat: Curling plus faded or scorched patches on sun-facing leaves. Move it out of direct sun.
- Tap-water minerals: Brown, crispy edges with curling that builds over weeks. Likely fluoride, chlorine, or salt buildup from hard tap water.
- Spider mites: Curling with fine webbing and tiny pale speckles. Check leaf undersides with a magnifier for moving dots.
How to fix it
- Water thoroughly until it drains from the bottom, then let the top inch dry before watering again.
- Raise humidity to 50 to 60 percent with a humidifier, pebble tray, or by grouping plants.
- Move the plant to bright indirect light, away from direct sun, heaters, and cold drafts.
- Switch to distilled water, rainwater, or tap water left out overnight to off-gas chlorine.
- Inspect leaf undersides for spider mites and rinse or treat with insecticidal soap if found.
- Trim fully crisped leaf tips and wait for healthy new growth.
| Symptom | Likely cause | First fix |
|---|---|---|
| Curl + dry soil + crisp edges | Underwatering | Water deeply |
| Even browning edges | Low humidity | Add humidifier |
| Scorched, faded patches | Too much light or heat | Move from direct sun |
| Slow brown-edge buildup | Tap-water minerals | Use distilled water |
| Webbing + speckling | Spider mites | Treat undersides |