Why does my Calathea have brown spots?

Calatheas most often get brown spots from the fluoride, chlorine and mineral salts in hard tap water, which burn the sensitive leaf tissue. Low humidity is the next most common cause, drying patches of leaf into brown spots, followed by direct sun scorch and inconsistent watering. Switch to filtered or distilled water first, then raise the humidity.

Most likely cause

Hard tap water is the top cause of brown spots on a Calathea. Calatheas are unusually sensitive to the fluoride, chlorine and dissolved minerals in treated tap water, and those compounds accumulate in the leaf tissue and chemically burn it, leaving brown spots and scorched tips.

You can confirm it by the pattern and your water. The spots are often small and scattered or concentrated at the tips and edges, sometimes ringed with yellow, and they tend to appear a day or two after watering. If you water straight from the tap and live in a hard-water or fluoridated area, this is almost certainly the driver. Switching to filtered, distilled or rainwater stops new spots, though existing damage stays.

Other causes

These rank below water quality but often stack with it.

Low humidity. Dry indoor air dries patches of leaf; look for brown spots paired with crispy edges when humidity sits below 50 percent.
Direct sun. Harsh light scorches the surface; the spots are tan to bleached and sit on the side facing the window.
Inconsistent watering. Drought-then-flood swings stress the foliage; brown spots appear alongside curling or drooping.
Leaf-spot infection. A fungus or bacteria attacks wet leaves; spots are often dark, water-soaked and ringed, and they spread over time.

How to fix it

Switch your water. Use filtered, distilled or collected rainwater; at minimum, let tap water sit out overnight so chlorine can off-gas.
Flush the soil. Run water through the pot every couple of months to leach out built-up salts.
Raise the humidity. Aim for 50 percent or higher with a humidifier or a pebble tray under the pot.
Move out of direct sun. Give the plant bright indirect light instead of harsh, direct rays.
Water consistently. Keep the soil lightly moist, watering when the top inch is just dry, and avoid wetting the leaves.
Trim and isolate if infected. If spots are dark and spreading, remove affected leaves, keep foliage dry, and isolate the plant from others.

Cause	Tell-tale sign	Fix
Hard tap water	Scattered spots and scorched tips	Switch to filtered or distilled water
Low humidity	Brown spots with crispy edges	Raise humidity to 50 percent or higher
Direct sun	Tan, bleached spots facing window	Move to bright indirect light
Inconsistent watering	Spots with curling or drooping	Keep soil evenly, lightly moist
Leaf-spot infection	Dark, ringed spots that spread	Remove leaves, keep dry, isolate

Frequently asked questions

Does tap water cause brown spots on Calathea?

Yes, very often. Calatheas are sensitive to the fluoride, chlorine and dissolved salts in hard tap water, which build up and burn the leaf tissue into brown spots and tips. Switch to filtered, distilled or rainwater to stop it.

Will the brown spots on my Calathea spread?

Mineral and humidity spots do not spread on their own once you fix the cause, though existing damage stays. Spots from a fungal or bacterial infection can spread, so isolate the plant, keep the leaves dry, and remove badly affected leaves.

Should I cut off Calathea leaves with brown spots?

Only if a leaf is mostly damaged. For small spots you can trim just the brown area, following the leaf shape, or leave it be. Remove a whole leaf at the base only when most of it is brown, and always fix the underlying cause first.

Can low humidity cause brown spots on a Calathea?

Yes. Calatheas are rainforest plants that want 50 percent humidity or higher, and dry indoor air dries out patches of leaf tissue into brown spots and crispy edges. Raise humidity with a humidifier or a pebble tray to prevent more.

Why does my Calathea get brown spots after watering?

This usually points to your water. The fluoride, chlorine and salts in tap water accumulate in the leaves and burn them, often showing up a day or two after watering. Use filtered or distilled water and let tap water sit out overnight at minimum.

How do I prevent brown spots on my Calathea?

Water with filtered or distilled water, keep humidity at 50 percent or higher, and keep the plant out of direct sun. Avoid wetting the leaves when you water, and keep moisture and conditions consistent to prevent stress spots.