Brown Spots on Monstera Leaves: Fungus or Sunburn?

Brown spots on monstera leaves are alarming, but they are also a clue, not a verdict. The same brown patch can come from a fungus, a sunburn, soggy roots, dry air, or a pest — and the fix for one cause can make another worse. Spraying a fungicide on a sunburned leaf will not help it, and moving a fungus-infected plant into brighter light will not cure it. This guide helps you tell the causes apart, starting with the question most monstera owners actually ask: is it fungus, or is it sunburn?

First, the honest part: a brown spot will not turn green again. Dead leaf tissue does not heal. Your goal is not to rescue the spotted leaf. It is to stop new spots, protect the healthy leaves, and get the plant growing clean new foliage again.

Quick diagnosis: Spots that showed up within a few days of moving your monstera into direct sun, on the side facing the window, are most likely sunburn. Small round spots with yellow halos that keep appearing on new leaves, especially when leaves stay wet, point toward a fungal or bacterial leaf spot. Mushy brown areas plus wet soil point toward root trouble — check the roots before you treat the leaves.

The 60-second triage

Before you treat anything, run these five checks. They take a minute and they prevent most misdiagnoses.

1. Where are the spots? Sun-facing side only suggests sunburn. Random spots all over the plant suggest infection or pests. Edges and tips first suggest dry air, salts, or watering trouble.
2. Feel a spot. Dry and papery means sunburn, dry air, or fertilizer burn. Soft and mushy means rot or advanced infection — act today.
3. Check the soil. Push a finger 2 inches down. Soggy soil that never dries out points to overwatering and root rot. Bone-dry soil pulling away from the pot points to underwatering.
4. Look underneath. Turn a few leaves over and look for fine webbing, tiny moving specks, or sticky residue. Pests hide on undersides.
5. Ask what changed. A move, a new window, a cold draft, a fertilizer dose, or a watering change in the last two weeks is usually the trigger.

Fungus or sunburn? The head-to-head test

This is the comparison that matters most, because the two look alike at a glance and need opposite fixes.

If you are still unsure after the table, treat it as an infection first: isolate the plant, keep leaves dry, and improve airflow. Those steps harm nothing if the cause turns out to be sunburn, while moving a sick plant into brighter light can make an infection worse.

What the spot pattern usually means

A spot pattern is a clue, not proof. Two causes often overlap — overwatering invites fungus, and dry air invites spider mites — so check soil, roots, and leaf undersides alongside the pattern, not instead of it.

1. Fungal leaf spot

What you see: Small to medium brown spots, often with yellow halos, scattered across leaves rather than starting at the edges. Spots may grow, merge, and appear on new leaves over days or weeks.

How to confirm: The spots keep appearing on leaves that were healthy last week, and leaves stay wet for hours after watering or misting. Poor air circulation and wet foliage make leaf-spot fungi far more likely.

Fix it:

1. Move the plant away from other houseplants until new spots stop appearing.
2. Remove the worst-affected leaves with clean shears, cutting at the stem base. Disinfect the shears with rubbing alcohol between cuts. Keep leaves that are only lightly spotted — the plant still needs them.
3. Stop wetting the leaves. Water at soil level, in the morning, so any splashes dry quickly.
4. Improve airflow with space around the plant and, if needed, a small fan nearby for part of the day.
5. Check drainage. A pot that holds water will keep feeding the problem no matter what you spray.
6. Only use a fungicide if it is labeled for houseplants and for leaf spot, and follow the label exactly. A spray is a backup, not the fix — dry leaves and airflow are the fix.

2. Sunburn

What you see: Large, dry, bleached-tan patches that turn brown, only on the side facing the window or the light. The rest of the plant can look perfectly healthy.

How to confirm: The spots appeared soon after the plant was moved, a curtain was removed, or the sun angle changed with the season. Monstera deliciosa prefers moderate brightness but not direct sunlight, so a south-facing windowsill in strong sun is a classic trigger.

Fix it:

1. Move the plant out of direct sun today — a few feet back from the window, or behind a sheer curtain, into bright indirect light.
2. Do not move it into a dark corner instead. Too little light creates a new problem while you solve this one.
3. Leave mildly spotted leaves alone. Remove only leaves that are mostly brown and crispy, since they no longer photosynthesize much.
4. Acclimate gradually if you ever move it back toward brighter light — a little more light over a week or two, not all at once.
5. Variegated monsteras burn faster than all-green ones, because the white areas have less chlorophyll to handle strong light. Give variegated plants the gentlest bright-indirect spot you have.

3. Overwatering and root rot

What you see: Mushy brown areas, leaves that droop or yellow alongside the spots, and soil that stays wet for days. This is the cause to rule out first when spots are soft rather than crispy, because it can kill the plant while you debate fungus versus sunburn.

How to confirm: Slide the plant out of its pot and look at the roots. Firm, pale roots are healthy. Brown, mushy roots that smell sour are rotting. If you are unsure whether the problem is too much or too little water, read overwatered vs underwatered before you change anything.

Fix it: Let the soil dry out, make sure the pot drains freely, and trim only the mushy roots if you repot into fresh, well-draining mix. Full rescue steps are in how to save an overwatered plant and root rot signs and treatment. Do not fertilize a plant while its roots are recovering.

4. Dry air and low humidity

What you see: Brown, crispy edges and tips that creep inward, usually in winter when heating dries indoor air. The spots are dry, not mushy, and the soil may be perfectly fine.

How to confirm: The damage starts at leaf edges, other tropical plants nearby show crispy tips too, and the air feels dry. A cheap hygrometer near the plant settles the question.

Fix it: Group plants together, run a humidifier near the plant, or use a pebble tray under the pot with the pot sitting above the water. Do not mist spotted leaves to raise humidity — wet leaves feed fungus, and misting barely changes room humidity. See how to increase humidity for houseplants for the methods ranked honestly.

5. Pests: spider mites and thrips

What you see: Tiny brown or yellow specks that look like dust at first, stippled leaves, fine webbing on leaf undersides (spider mites), or silvery streaks with tiny black specks (thrips). Damage often starts on lower or older leaves.

How to confirm: Hold white paper under a leaf and tap it gently. Moving specks on the paper mean pests, not disease. Check leaf undersides with your phone flashlight — that is where both pests feed.

Fix it: Isolate the plant, rinse the leaves thoroughly to knock pests off, then treat with insecticidal soap or neem oil exactly as labeled, and repeat every 5 to 7 days for several weeks — one spray never finishes the job, because eggs keep hatching. Follow the full plans in how to get rid of spider mites and how to get rid of thrips.

6. Fertilizer burn and mineral buildup

What you see: Brown leaf tips and edges after a recent feeding, sometimes with a white crust on the soil surface or pot rim. Hard tap water can build up salts the same way over months.

How to confirm: The damage followed a fertilizer dose, a double dose, or feeding a dry plant. Check for that white crust — it is the giveaway.

Fix it: Stop fertilizing, flush the soil thoroughly with plain water and let it drain completely, then wait. Resume feeding only when the plant is growing again, at half the label strength, and never on dry soil.

7. Cold damage and drafts

What you see: Dark, sometimes water-soaked patches that appear after a cold night, a window left open, or a plant sitting against cold glass. The damage often shows on the leaves nearest the cold source.

Fix it: Move the plant away from the draft and cold glass, trim only tissue that is fully dead and dry, and keep watering steady while it recovers. Cold-damaged leaves will not recover, but the plant usually pushes new growth once it is warm and stable again.

8. Old leaves and everyday bumps

What you see: A single oldest, lowest leaf turning brown while the rest of the plant looks healthy, or a brown patch where a leaf was bent, rubbed, or brushed against something.

Fix it: Nothing, most of the time. Old leaves age out naturally, and a bumped leaf will scar but not spread. Remove the leaf only when it is mostly brown. If new leaves keep spotting, you have one of the causes above, not old age.

What not to do

• Do not spray a fungicide on sunburn and hope for the best — it adds chemical stress to an already damaged leaf.
• Do not cut off every spotted leaf at once. A lightly spotted leaf still feeds the plant, and stripping it bare slows recovery.
• Do not mist spotted leaves. Wet foliage is exactly what leaf-spot fungi want.
• Do not repot, fertilize, and move the plant all on the same day. Change one thing, watch for a week, then change the next.
• Do not move a sunburned plant into a dark corner. Bright indirect light is the goal, not darkness.

Recovery timeline

Brown spots themselves never fade. Recovery means no new spots and healthy new leaves, and it takes longer than most guides admit.

• Week 1: New spots should slow down once the cause is fixed. Existing spots stay exactly as they are — that is normal, not failure.
• Weeks 2 to 3: Look for new growth from the growing points. If spots are still spreading fast, your diagnosis is probably wrong — re-run the triage, especially the root check.
• Month 1 to 2: New leaves should come out clean. In dim winter light, growth is slower, so judge by new leaves, not by speed.
• Red flags: Spots spreading to most leaves, stems turning soft, or a foul smell from the soil mean the roots or stem are involved. Treat that as urgent, not cosmetic.

When to give up on a leaf — or the plant

Give up on a leaf when it is more than half brown, fully crispy or mushy, or clearly infected and spreading. Cut it at the stem base with clean shears and discard it — do not compost diseased leaves near other plants.

Give up on the plant when the stem is soft and mushy through, there is no firm stem or healthy node left, or rot has reached the crown despite a proper root trim and repot. A monstera with firm stems and even one healthy node can still come back, so do not discard a plant just because its leaves look rough. Ugly leaves are not a dead plant.

How to prevent brown spots

• Bright indirect light, never harsh direct sun — acclimate gradually to any brighter spot.
• Water when the top 2 inches of soil are dry, water at soil level, and always let the pot drain.
• Keep leaves dry, give the plant airflow, and wipe dusty leaves with a damp cloth now and then.
• Quarantine new plants for two to three weeks before placing them with your collection.
• Feed lightly and only while the plant is actively growing.
• Check leaf undersides monthly, so pests are caught when they are a few specks, not an infestation.

Related rescues

• Why Is My Monstera Drooping?
• Why Are My Monstera Leaves Turning Yellow?
• How to Get Rid of Spider Mites on Houseplants

Also see your monstera hub, how often to water a monstera, and the monstera care guide for the full routine that keeps new leaves spot-free.