PlantRx

Begonia leaves turning brown

By Karim DiabatePublished Updated How these guides are built

Brown on a begonia leaf is dead tissue, so the useful question is not how to bring it back, because it will not come back. It is what killed it, and whether it is still happening. Where the brown starts is the clue.

A healthy Begonia, photographed for reference
A healthy begonia for comparison. This is a reference photo, not a picture of the problem. Photo by Cliff (CC BY 2.0), via Wikimedia Commons.

What is specific to this plant

  • Begonias want humidity but hate wet leaves, which is an awkward combination and the reason powdery mildew is so common on them.
  • Water on the foliage in a still room is the usual trigger. Airflow matters as much as watering.
  • Many begonias die back and rest seasonally, so a plant thinning in autumn may simply be resting.

What it could be, and how to tell

These look alike in a photograph, so each one below lists what you would ALSO see if that is the cause. Work down the list and stop at the one where the other symptoms match too.

most common

1. Wet leaves in a room with no air moving

What else you would see

  • a dusty white bloom on the upper leaf surfaces
  • patches that spread across leaves over days
  • water visibly sitting on the foliage after watering
  • a humid position with the plant crowded against others
How to confirm it: Look at whether the leaves are getting wet and whether the air is moving. A begonia wants humidity but cannot tolerate water sitting on its foliage, which is an awkward combination and the reason mildew is so common on them. Wet leaves plus still air is the pairing; humidity on its own, with airflow, is not a problem.

What to do

  1. Water the mix only, never over the leaves, and never mist this plant.
  2. Get air moving around it and space it away from its neighbours.
  3. Remove the worst affected leaves rather than leaving them as a source.
common

2. Underwatering, or letting it dry out too far

What else you would see

  • edges crisping on the largest leaves first
  • a fast wilt that reverses within an hour or two of watering
  • buds dropping before they open while the foliage still looks well
How to confirm it: Dry soil pulled away from the pot wall, with foliage that improves noticeably within a day of a thorough soak. If a thorough watering changes nothing in twenty four hours, stop assuming thirst and check the roots.

What to do

  1. Water thoroughly until it runs freely from the drainage holes, rather than a splash at the surface.
  2. If the mix has gone water-repellent and the water runs straight through, stand the pot in a basin of water for half an hour to rewet it properly.
  3. Water on dryness rather than on a fixed day of the week, and this is how far it should dry: the top inch.
common

3. Overwatering, and the root rot that follows

What else you would see

  • stems collapsing at the soil line while the leaves above them are still firm
  • grey mould on fallen flowers or leaves left lying on the mix
  • the lowest leaves going soft and dark rather than crisp
How to confirm it: Slide the plant out of its pot and look at the roots. Healthy ones are fine and pale. Brown, soft, or hollow when you press them means rot, and that changes what you do next completely.

What to do

  1. Stop watering and let it dry down this far: the top inch.
  2. Check that the pot drains and empty any saucer or decorative outer pot it sits in. Water held out of sight keeps the mix wet whatever you change above it, and it stays invisible until you lift the pot.
  3. If the roots are soft and brown, trim them back to firm tissue with a blade sterilised first and repot into fresh light, airy, free-draining mix.
less common

4. Too much direct sun

What else you would see

  • bleached, pale patches rather than an even colour change
  • damage only on the side or the leaves facing the window
  • leaves warm to the touch in the afternoon
How to confirm it: The pattern settles it: sun damage is one-sided and patchy, while watering problems and ordinary ageing are even across the plant.

What to do

  1. Move it back from the glass or filter the light. Begonia wants bright indirect light.
  2. Bleached tissue does not turn green again. Judge recovery by whether NEW leaves come in a healthy colour.
less common

5. Dry air

What else you would see

  • worse in winter once the heating is on
  • a radiator, a vent or a draught nearby
  • other plants in the same room showing crisp edges too
How to confirm it: Seasonal timing, and more than one plant in the room affected at once. That points at the room rather than at anything you did to this plant.

What to do

  1. Move it away from direct heat sources and draughts.
  2. Group plants together, or stand the pot on a tray of damp pebbles, so the air immediately around it is more humid.
uncommon

6. Minerals and fluoride in tap water

What else you would see

  • damage confined to the very tips and outer edges, with a thin yellow band between the brown and the green
  • a white or yellowish crust on the surface of the mix or around the pot rim
  • the plant otherwise growing well, and still producing new leaves
How to confirm it: Tip-only damage on a plant that is otherwise thriving. Begonia is in the group that reacts to what is dissolved in tap water rather than to how much of it you give.

What to do

  1. Switch to filtered, distilled or rainwater.
  2. Flush the pot every few months: run a large volume of water slowly through it so accumulated salts leave through the drainage holes.
  3. Trim the damage at an angle with clean scissors, leaving a hairline of brown so you do not cut into living tissue and create a fresh brown edge.
uncommon

7. Cold or a draught

What else you would see

  • damage that appeared within a few days of a cold snap, or of the heating or air conditioning coming on
  • the plant sits near a window, an exterior door or a vent
  • the damage is worst on the side facing the cold
How to confirm it: Sudden onset on the exposed side only, following a temperature change. A leaf resting against cold glass overnight is enough to do it.

What to do

  1. Move the plant away from the glass, the door or the vent.
  2. Damaged tissue will not recover. Leave it unless it turns soft, which is the point at which it can start to rot.
uncommon

8. Ordinary ageing

What else you would see

  • one or two of the oldest, lowest leaves at a time and no more
  • healthy new growth continuing from the centre or the tip
  • no other symptom anywhere on the plant
How to confirm it: Oldest leaves only, while the plant is still producing new ones. A plant funding new growth from its oldest tissue is working normally.

What to do

  1. Remove the spent leaf at its base with a clean blade, purely for looks.
  2. Nothing else is needed.

Common questions

Should I cut brown leaves off?

Once a leaf is more brown than green, take it off at the base. If only part of a leaf is brown, you can trim the dead section at an angle and leave the rest, since a partly green leaf still does useful work.

Will the brown parts recover?

No. Brown tissue is dead and stays dead. Success is measured by whether the NEW leaves come in clean, which takes a few weeks after the cause is fixed.

Crispy brown or soft brown, does it matter?

It matters a great deal. Crispy and dry points at too little water, dry air or sun. Soft, dark and damp points at too much water or at a rot, and those need opposite responses.

Before you act on any of this

This is general plant care guidance for a plant, not advice about people or animals. We never tell you whether a plant is safe to eat or touch, and we never tell you a plant is safe for a child or a pet. If a child or animal may have eaten any part of a plant, contact Poison Control (US 1-800-222-1222) or a vet immediately rather than reading further.

Treatment advice here is deliberately category level. We do not give product names, mixing ratios or application intervals. Whatever the label on the product in your hand says is the instruction that counts, and following it is your responsibility.

Where this comes from

The general horticultural facts behind this differential come from published university extension and Royal Horticultural Society guidance. What is specific to this plant, and the order the causes are ranked in, is ours, and the methodology page says where that reasoning stops being reliable.

Other begonia problems

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