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First of all BREATH. We’re going to get to the bottom of what causing black or brown spots to appear on your Monstera. This is going to be fine.
There are 8 reasons why your monstera is developing black or brown spot on its leaves:
- Root rot
- Physical damage
- It’s too cold
- Not enough humidity
- You’ve been misting
- It’s not getting enough light
- It’s diseased.
Before you panic, I’ve listed these causes in order – i.e. the brown spots are way more likely to be caused by root rot. Disease is probably unlikely.
And root rot isn’t necessarily the end. It’s not great, but they can recover.
Brown or black marks on Monstera leaves don’t always mean there’s an issue with the plant – it may just be one leaf that’s having trouble with something.
The main obstacle when it comes to spots on Monstera leaves is diagnosis. It’s NOT easy. Sunburn can look like root rot. Root rot can look like fungus. Over time you can become better at identifying issues, but it’s not an exact science.
Black spots on Monstera can be caused by root rot
Root rot is extremely common in plants, usually because we love to over water them. Other signs of root rot are yellowing leaves.
Plants don’t need watering nearly as much as we think (there’s an article here that’ll teach you how to do it properly), and they can get root rot extremely easily.
The good news here is that Monstera deliciosa are, in my experience, pretty hard to push past the point of no return. I mean if you want to be rid of one, overwatering is absolutely the way to go, but also, they can be brought back from it.
Once the leaves have blackened, browned, or turned yellow, it’s irreversible. The leaf might not drop, but it won’t return to its original green.
I have an article here that will go through exactly how to rehab your plant. In short, you’re going to need to cut off any sad-looking leaves (provided you have at least one left), and roots, take the plant carefully out of its pot, gently wash the soil off the roots, and put it in a jar of fresh, room temperature water.
Make sure only the leaves are in the water. Change the water every couple of days and wait for new roots to grow.
Root rot is caused by bacteria attacking the roots. The roots will go mushy and smell, er, gross, and will no longer work efficiently. But as I mentioned before, roots can regrow, and pretty quickly in Monstera.
There’s often a little bit of confusion around putting an overwatered plant in water, but let me explain.
Plants that are growing in water grow water roots, plants that are growing in soil grow soil roots.
They both do the same thing – extract oxygen from their surroundings – but in slightly different ways.
A more extreme way to think of it is like how humans can get oxygen by breathing in the air (but will drown in water) and fish are the opposite way around.
Plants can develop a root system that best suits their surroundings.
Black spots on Monstera can be caused by dehydration
Or, as professional people call it ‘incongruent watering’.
Monstera like a lot of water, but only when they’re dry.
Watering once a week is often far too much, especially in colder climates, or if your Monstera is in a low light situation.
If you’re unsure, pick up a moisture metre (they’re pretty cheap) and only water when the needle points to 2.
If you keep watering your plant and the soil is drying out really quickly then try bottom watering your plant.
Leave it to soak in a couple of inches of water until the top of the soil is damp.
If you have a big monstera, you can do this in the bath.
Soil can become hydrophobic, and not absorb any water.
Instead, the water runs in the gap between the soil and the plant, and through any cracks in the soil. Giving it a soak rehydrates the soil thoroughly, and helps it hold water again.
If the soil is still drying out in a couple of days, check that the plant isn’t rootbound.
The roots will displace the soil so the there’s not enough soil to hold an adequate amount of water.
If the roots are almost entirely encircling the rootball, it’s time to re-pot.
Don’t be tempted to dramatically increase the size of the pot, because you’ll end up with the opposite problem, and the plant could be at risk from root rot.
A pot a couple of inches bigger is fine.
Black spots on Monstera can be caused by sun burn
Wild Monstera (as it were) live in rainforests, below the canopy. They don’t get a lot of bright, direct light, so if they are exposed to it, then they can get burned.
This is especially true if you have a variegated Monstera – they burn incredibly easily.
Now the conflict we have here is that in order for your Monstera to grow those big, beautiful fenestrated leaves, it needs A LOT of light.
If you’re lucky, you have a room filled with bright, indirect light. If you have a south-facing room with great windows, put the Monstera next to window, but hang a sheer curtain.
This should stop the plant from burning.
Alternatively, you can gradually increase your plant’s tolerance to the light – this is time-consuming and always carries a risk of burning.
If you have a warm enough climate your Monstera could grow into a BEAST if you acclimatise it to living outdoors. Put it somewhere where it gets nice light but is shielded from the strongest rays – under a porch or shady tree would be good.
I have an article here about acclimatising your plants so they can live outside in the summer.
Personally, I keep my Monstera in an east-facing window. Sure, he may never grow enormous (or he’ll take a while to) but he won’t burn. My Thai Constellation is in a bright, south-facing room but five feet away from the window so she doesn’t get any direct sun.
You can try grow lights if your Monstera lives in a low light situation and you don’t want to move it.
I have these ones and they get the job done without burning the plant.
Variegated plants are WAY more susceptible to sunburn than green plants because the chlorophyll is a layer of protection.
I don’t think this plant is actually burnt because it’s a way away from the window, but I would still consider this sun damage. See how crispy it looks?
Black spots on Monstera can be caused by physical damage
Especially on new growth. Plants don’t like being touched, and you can easily cause damage by touching new growth, however lightly.
I’m as guilty as anyone for trying to sneak a peak at a newly unfurling monstera leaf (there could be holes!) but try not to.
As well as new growth, plants can get damaged in transit. If the black spots on your leaves look quite straight, it’s probably old damage. If a plant was packed in tightly with others and had a leaf bent back, that can leave a scar.
If the leaf is young, not only is it more delicate, but it may still be growing.
Something happened to my baby Monstera and now it has a gnarly leaf tip. I still love him the same.
A small scar you didn’t notice might look huge by the time the leaf has finished growing.
The scar may also change and get a brown edging as the plant tries to heal itself.
Black spots on Monstera can be caused cold temperatures
Tropical plants hate the cold. The biggest culprit of black spots caused by the cold is unheated sunrooms or conservatories.
They remain warm during the day until quite late in the year (especially if they’re south or west-facing) but get really cold at night.
Fun fact: my mum killed a Sansevieria (yes – she’s got that much of a black thumb) by leaving it in the conservatory over winter.
I’m not 100% if the plant starts self-destructing as a way of conserving energy – like a form going dormant – or if the cold weather and immuno-compromised plant attract fungal diseases.
I think it’s probably the latter. The problem with glass rooms is that they give the plant a lot of light, so the plant tries to continue growing when it really doesn’t have the resources. Either keep the room warm or move your plant to a warmer spot.
Plants that are kept in a cold spot for a few hours can look FAR worse than mine below. I actually think this spot was caused by watering it with too-cold water when the leaf was still new. It’s just a theory though.
Black spots can be caused by low humidity
Monstera aren’t THAT fussy about humidity. They grow better with high-ish humidity, but it’s not the end of the world if you live somewhere pretty dry. But you may end up with brown, crispy edges to your leaves.
If you have low humidity (ie. less than 40%) consider getting a humidifier. It’s the only way to provide constant humidity to your plants. If you have medium humidity try these tricks to increase your humidity without a humidifier.
To be honest, Monstera will happily live in 40% humidity. But if you want optimal growth and massive leaves, try to increase your humidity to around 65%.
Black spots on Monstera can be caused by too much misting
Plants don’t like getting their leaves wet – it cause the leaves to rot (which will lead to black spots) or it’ll lead to fungal and bacterial diseases (again which will lead to root rot).
I have a whole article on why I think misting is a waste of time, but there are people that swear by misting, so it’s up to you to decide which side of the fence you want to sit on.
Whilst misting can cause brown spots, remember that Monstera come from tropical rainforests, where it, er, rains, so they won’t die if they get wet leaves.
Monstera in the wild often look quite gnarly, since they’re sometimes exposed to brighter light (especially if they’re growing somewhere more exposed – there’s some massive wild ones in Florida) that they’re evolved to deal with.
I guess that’s the price you pay for being an invasive species!
(I joke. I think it’s mad that plants get accused of being invasive when it’s humans that moved them. When it comes to staying still, plants are great at that. You can’t tell me a Monstera climbed from Brazil to Hawaii with no help).
Black spots on Monstera can be caused by not enough light
I personally don’t think this is very likely, unless your plant isn’t getting any light at all, but it can happen.
Monstera are pretty tolerant of low light situations, but they do best in bright, indirect light. Whether this is the cause of your brown spots or not, giving your Monstera more light will definitely help it grow.
Just, you know, don’t put it directly in a south-facing window.
Again, grow lights are an option.
Black spots on Monstera can be caused by disease
If you’ve exhausted all the other possibilities, your plant could have a disease. Cut off the affected leaves, and read this post on how to give your Monstera great conditions and help it grow.
Be sure to check any nearby plants for signs of disease too.
Your Monstera may have pests
The most common pest that afflicts Monstera is, in my experience. Thrips.
Thrips are a pain. A nightmare.
But they probably won’t kill your plant unless you let them run wild. They’ll just make it look TERRIBLE. Here’s my sad looking specimen with a touch of thrips damage.
Thrips and other pests don’t normally cause the black spots BUT they are attracted to comprised plants and can make the problem worse.
If you look closely, you can actually see the thrips here. They’re the little green/yellow blobs that look like teeny grains of rice.
The big brown spot at the top isn’t anything to worry about. It’s just a result of…winter. The humidity is lower, as is light, and plants are just less resistant to any hardship that comes their way.
But the little spot just above? That’s thrips. Those little sods.
Should I remove the leaf if there’s a brown spot?
It depends. Unless the leaf is diseased or rotten, the brown leaf won’t harm the plant. It won’t turn green again though.
I tend to snip off badly affected leaves and trim the smaller brown spots out of leaves if I can. It’s really a judgement call. Leaves will only a small amount of browning will still help photosynthesis, so it’s in the interest of the plant to leave it be.
Final thoughts on spots on Monstera
- If the spot is mushy it’s probably root rot – re pot and rehab if it’s really bad
- If the spot is crispy it’s probably sunburn or dehydration – move it and water it
- If the spot is super dark and there are a few and they look kind of uniform it’s probably a disease. Snip snip, clean the leaves with a dry microfibre cloth and monitor it.
Don’t overpay for your Monstera!