PlantRx

Anthurium brown spots on leaves

By Karim DiabatePublished Updated How these guides are built

Brown spots on an anthurium have several possible causes whose treatments contradict each other, so guessing is expensive. Where the spot sits on the leaf, and whether new leaves are affected too, narrows it faster than anything else.

A healthy Anthurium, photographed for reference
A healthy anthurium for comparison. This is a reference photo, not a picture of the problem. Photo by Taken by Fanghong (CC BY 2.5), via Wikimedia Commons.

What is specific to this plant

  • Anthuriums are epiphytes. Potted in ordinary dense potting soil they suffocate slowly, and the symptom that follows looks exactly like overwatering because it is.
  • The coloured part is a spathe, not a petal, and it browning with age is ordinary rather than a sign of illness.

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. Wedge-shaped marks spreading in from the leaf edge

What else you would see

  • V-shaped patches pointing inward from the margin toward the midrib
  • a yellow halo ahead of the advancing edge
  • the marks growing over days rather than staying fixed
  • a warm humid position with little air movement
How to confirm it: Look at the shape and whether it is advancing. An anthurium leaf drains toward its margins, so infections entering at the edge spread inward along the veins and produce a characteristic wedge with a yellow front. A wedge that is bigger this week than last is spreading and needs the leaf removed; a fixed mark with no halo is old damage.

What to do

  1. Remove affected leaves entirely and get air moving around the plant.
  2. Keep water off the foliage and water the mix only.
  3. Space it away from its neighbours while it settles.
common

2. Root rot showing up in the leaves

What else you would see

  • dark brown or nearly black spots starting at the base or the centre of the leaf and spreading outward
  • the lowest and oldest leaves affected first, working upward
  • mix wet for days, when this much should have dried: the top inch or two
How to confirm it: Slide the plant out of its pot and look at the roots. Healthy ones are thick, firm 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 or two.
  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 very airy, bark-heavy mix.
common

3. Dryness

What else you would see

  • tan or light brown crispy patches starting at the EDGES and tips
  • leaf edges curling inward
  • mix dry and shrunk away from the pot wall
How to confirm it: Crispy and light coloured, starting at the outside and working in. That is the opposite direction to root rot damage, and the direction is the single most useful distinction available here.

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 or two.
less common

4. Bacterial or fungal leaf spot

What else you would see

  • irregular spots with a yellow halo around them
  • NEW leaves affected as well as old ones
  • noticeable spread over days rather than weeks
How to confirm it: New growth affected as well as old, with yellow haloes and fast spread. A watering problem works from the oldest leaves upward and respects that order; an infection does not.

What to do

  1. Isolate the plant from your others immediately.
  2. Remove affected leaves with a sterilised blade and dispose of them rather than composting them.
  3. Increase airflow, stop misting, and keep water off the foliage.
  4. If you choose to use a treatment product, follow its label exactly. The label is the legal instruction and overrides anything here.
less common

5. Sunburn

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. Anthurium wants bright indirect light.
  2. Bleached tissue does not turn green again. Judge recovery by whether NEW leaves come in a healthy colour.
uncommon

6. Physical damage or edema

What else you would see

  • small isolated marks that do not spread and have no halo
  • marks where a leaf rubs a wall, a pot or another leaf
  • small raised blisters on the underside after a heavy watering
How to confirm it: The mark does not grow over a couple of weeks and no new leaves are affected. Nothing that spreads is physical damage.

What to do

  1. Nothing to treat. Give the plant room so its leaves are not rubbing against anything.
  2. For blistering, water more evenly rather than in large infrequent soaks.

Common questions

Do brown spots spread from leaf to leaf?

An infection does, and it will reach new growth as well as old. Root rot damage appears on several leaves too, but always working from the bottom of the plant upward. Sunburn and physical damage do not spread at all.

Should I remove the spotted leaves?

Remove badly affected leaves, and remove them promptly if you suspect an infection, using a sterilised blade. A leaf with one small stable mark can stay, since it still does useful work.

Will the spots go away?

The existing spots never do. Judge whether you have fixed it by whether the new leaves come in clean.

Is an anthurium poisonous to cats, dogs or children?

Anthurium contains calcium oxalate crystals and is widely listed as harmful to pets and children if chewed. We do not tell you that any plant is safe. If a pet or a child may have chewed any part of one, contact a vet, or Poison Control on 1-800-222-1222 in the US, immediately rather than waiting to see what happens.

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 anthurium problems

Not sure which one it is?

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