Every gardener has at least once experienced their monstera turning black to some degree. It can have black dots on the leaves, entire leaves colored in black, or even the entire plant turning black. These are all signs of physiological plant stress.
Monstera turning black due to Environmental and physical factors like Improper watering, Dry soil, Environmental issues, Lack of exposure to sunlight and Humidity problems. In addition monstera Diseases, Pest infestation or physical damage can cause this issue.
I will address some of the most common causes for these phenomena and give approximate solutions for them. Keep reading to help your monstera heal right back up.
Contents
Causes of Monstera Turning Black
Improper Watering
Water issues are the most common causes of black spots on monstera leaves. It’s important to check your water quality and dosage. Only then can you routinely water your glorious plant. Most people take watering their plants, monstera included, for granted and only do it when they deem it fit.
But just like in many things, moderation is key for success. There’s no answer to ‘How long should I water my monstera?’ because every plant has different needs.
Water Quality
Most gardeners use tap water for watering, so it’s important to make sure it’s drinkable for the plants. If you suspect your water contains contaminants, like chlorides and fluorides, I recommend contacting your water community to give you a quality report.
Inadequate liquids can cause black spots on the leaves. It’s like drinking poison for them. Salts in the water can clog the plant’s water transporting system.
Solution
Try using a faucet water filter if you want to improve water quality. I normally use room-temperature water. Melted snow water and rainwater can be used too! A quick tip: leave it to sit overnight so chemicals, like chlorine, and other salt-forming components, have enough time to evaporate.
Overwatering
Overwatering and monstera – name a more iconic duo. Because of its enormous size, you may feel obligated to pour massive amounts of water into the plant’s soil. Overwatering sometimes leads to root rot.
As a result, your plant gets big dark patches on its leaves. Take preventive actions as early as possible because these patches tend to spread quickly!
Solution
Keep track of your watering schedule! Put your finger or a wooden stick about 2 to 3 inches (5-7.5 cm) deep into the soil. If it’s dry, it might be time to water your plant.
If it’s damp, wait a couple of days for the plant to absorb the moisture. Monstera needs water every 7 to 10 days. When watering, make sure to soak the soil completely, and please don’t water the leaves, just the soil!
Dehydration
On the other side of watering extremes, you have dehydration. Unlike overwatering, underwatering is a slow killer. This process takes a lot longer to show up compared to overwatering because monstera has thick leaves. The dehydrated plant doesn’t have enough water to supply every part of it.
This is why blackness and crispiness first show on the most far-out leaves. Lack of water causes plant stress which leads to shutting down palisade cells. Juvenile leaves are closer to the stem, so they get the water first. A common sign of dehydration is dark brown-to-black crispy edges around leaves, followed by wilting.
Solution
If your monstera looks sad and droopy, covered with black spots, buy her a drink! I recommend soaking the bottom part of the pot in water and wait for the soil to absorb it. If this doesn’t work, it may seem your soil has become hydrophobic. It’s just a fancy expression for “it hates water”.
This happens on some occasions, especially if you keep your plant in strong indirect sunlight. You should re-pot the plant as soon as possible, preferably in a bigger pot with fresh new soil, and move it to a different place.
Dry Soil
Exposing the soil to a strong indirect light source can quickly turn it extremely dry. Now, dry soil isn’t a direct cause of black marks on stems and leaves, but it favors the development of various other symptoms. Unsuitable soil may have a low retention capacity, which leads to bad absorption, dehydration, and many nutritional inconveniences.
Dry soil is usually a result of bad sunlight management. Before potting (or repotting) your monstera, you can’t leave the soil exposed to direct or strong indirect sunlight. It becomes parched and hydrophobic.
Another cause of dry soil can be bad drainage. If you use compact soil, that’s heavy on the clay, the water won’t flow through it and it will stay dry at the root level.
Solution
Make sure your soil is in indirect light and it gets just enough water. If the soil is too compact, try mixing it with gravel and pebbles. According to research, gravel and pebble mixture can improve soil drainage, and maintain soil temperature and humidity.
If you assess that the soil is beyond help, make sure to re-pot your monster in a pot with quality, humus-rich soil.
Another issue you might come across is having black stems and roots.
I definitely recommend repotting your plant in this case and switching soil mixture with good drainage properties.
I always recommend using orchid bark – it’s a bane for a terrible drain. You can use volcanic rocks, like perlite and organic vermiculite too! They’re all available on Amazon. Keep an eye on the repotted plant and observe if the spotting stopped or if it continued to spread.
Temperature Issues – Cold Temperatures and Sunburns
Each plant has its unique temperature minimum, maximum and optimum. These values tremendously impact plant growth, especially in juvenile stages.
Being a tropical plant, monstera likes pleasant and cozy places where it can bask in the warmth of indirect sun rays. Violation of these terms results in birthing large, unpleasant black dots all over the plant, from its roots to its leaves.
Cold Stress
When it comes to taking care of your plant, low temperatures are easily overlooked as a problem. Most people are afraid of sunburns and extreme heat, but cold weather is also a damaging factor. Because of their gargantuan size, monsteras can’t really tolerate the low temperature.
Such a big plant needs a lot of energy to warm up. The lowest they can withstand is around 50° F (10° C). Anything lower than that WILL damage your plant. Frost freezes the sap and water in the leaves. The plant can’t transfer nutrition to this part anymore and it turns black.
For the same reasons, low temperature can also damage new buds or cuttings for propagation which renders them dark and damaged. This kind of environment causes the plants to stop their growth, which results in black spots on the leaves. Low temperatures are also suitable for the development of many fungal and bacterial diseases.
Solution
Obviously, move your plant to a warmer place. I see people make one common mistake all the time, and that’s that they keep the plant area warm only during daylight. If you have a conservatorium (greenhouse) or windowed room for plants, you might sometimes forget to keep the place above 50° F (10° C) during the night, too.
Just because it’s warm during the day, doesn’t mean the night will also be comfortable. The bottom story is – keep the monstera’s bedroom warm at an optimal temperature of 64-75° F (18-24° C)!
Heat Stress – Sunburn
A more common temperature-related problem is sunburn. It’s a rookie mistake to get your plants burnt, but it’s something you learn quickly how to solve. By putting your monstera in direct sunlight, in front of a window, or even under a lamp, you’re exposing it to massive amounts of energy as heat.
You can quickly spot dark, rather crispy, and toasty patches on the leaves and stems of your plant. They are mostly oval-to-round in shape. Some people also like to leave their monsteras outside if it’s a nice day and place it on a heated patio which can significantly damage both leaves and roots.
Solution
Don’t place your monstera in front of a window, especially south-oriented ones. Ideally, you would place it near an east-looking window. This way, it can get a lot of indirect sunlight and warmth throughout the day. If you intend to carry your plant outside, make sure it’s in a shade and the ground you’re placing it onto isn’t too hot.
Not Enough Sunlight
Overwatering, low temperatures and insufficient sunlight are closely related. Water evaporation and photosynthesis depend on the amount of sunlight. Even if you use the right amount of water, it will stick to the surface because of the meager amount of indirect sunlight. This can cause yellow, sometimes dark discoloration on the leaves.
Insufficient sunlight can decrease the concentration of chlorophylls, small bodies responsible for turning natural light into energy. They’re present in all green parts of the plant. Without them, the plant becomes dark and gloomy.
Solution
Move your plant to a place with more natural light. Still, make sure it’s not in direct light or too close to windows because that might cause sunburns.
Humidity problems
Watering irregularities are often caused by humidity problems. Monstera can endure high humidity since it’s native to tropical rainforests, but low humidity is never a good thing. Low concentration of humidity and needless misting are the most common culprits for faulty humidity.
Low Humidity
If your plant suddenly starts asking for more water, a chance is that it doesn’t like the humidity of the room. By chugging more water, it’s trying to quench the thirst it would otherwise get from water particles in the air.
Just like its predecessors, your monstera wants to grow up in a tropical environment, so it’s imperative to keep a proper humidity level. As a result of low humidity, your plant will become droopy and covered in mold-like black smudges on some leaves.
Solution
If the soil quickly dries after watering, raise the humidity in the air. If you’re on a tightrope, you can always buy a small plant humidifier. However, try fixing things first by putting pebbles soaked in the water around the bottom of the pot. This way, the water will slowly evaporate into the soil and leaves. Monstera thrives in 50% to 60% humid areas.
Misting
For some reason, misting is becoming more and more popular among inexperienced gardeners. I don’t know why they resort to this technique as a way of raising humidity levels, but I’m strongly against it. Misting is a strategy where you take a spray bottle, fill it with water, and spray the plant with it.
The problem is, the thing that comes out of that bottle is not mist. Sorry, but that’s straight-up rain – and plants don’t like that. It can cause water to amass on the surface of the leaves, which is ideal if you want fungi and insects on your plant, and eventually leads to darkened spots on those leaves.
Solution
Don’t mist your monstera by spraying water on it. Simple as that! Only resort to this strategy if you live in a dry area and can’t afford a plant humidifier. In that case, mist, or should I rather say spray, the plant gently multiple times a day in smaller doses. Try sticking to a misting schedule, usually only every 3-4 days.
Inadequate Fertilization
Proper fertilization seems a big mystery for beginner gardeners. Not providing your monstera with enough nitrogen can lead to degenerative growth and indications of black and yellow spots. Insufficient nutrition leaves your plant hungry and prone to disease attacks.
Solution
Start by using a granulated fertilizer in juvenile growth. I recommend ones that are heavy on the nitrogen side. When the plant promotes leaf growth, try adding liquid urea, which is an organic, nitrogen-based fertilizer. During the mature stages, use a 20-20-20 (nitrogen-to-phosphorus-to-potassium ratio) liquid fertilizer.
Diseases
This is where things can get spooky! Every disease has unique symptoms, and it’s important to recognize them as soon as possible. Just because they aren’t exposed that much to pathogens, doesn’t mean that houseplants are safe from them.
Monstera is, unfortunately, susceptible to root and stem rots. Another disease I want to discuss is caused by fungus and it’s called anthracnose.
Root and Stem Rot
There are two causes for these diseases – one is overwatering and the second one is a fungus. I’ve already described overwatering, so here’s a quick summary: too much water is bad. Basically, water clogs absorbent (root) hairs and leaves the plant deprived of nutrition, oxygen and prevents osmosis.
The result is dark, mushy roots that dissipate when touched. This blackness quickly spreads to monstera stems too. Fungi, such as Rhizoctoma solani, have a similar effect. They penetrate the plant’s body with mycelium, blocking the xylem pathways, and robbing the plant of water and nutrition.
The symptoms are very much the same as rot caused by overwatering, except you can really feel the smell.
Solutions
Get that nasty habit of overwatering out of your head already! Don’t let your monstera swim in the pot.
Take the plant out of the pot, wash its roots, and use small-scale gardening shears to trim the diseased parts.
Always disinfect all the tools you use. Repot the plant in a pot with new soil. I always recommend creating and sticking to a watering schedule!
Anthracnose
This deadly disease is caused by the fungus Colletotrichum sp. It leaves oval, necrotic pieces of leaf tissue, mainly near the main vein.
If your plant has been severely exposed to the fungus, the leaves might curl up and fall off on their own. Anthracnose can first appear as yellow and brown spots.
This means that the fungus has entered the leaf tissue and is taking all the nutrients and water for itself.
The leaf is starved and darkens when there is no more water left in it. This fungus spreads only when it’s black because it’s seeking to expand.
Another thing that might cause dark spots is the plant’s immune system. The plant stops the flow of food to the infected part of the leaf, sacrificing it to prevent anthracnose from spreading.
Solution
Cut the entire leaf off if most of its surface has already been damaged. Use garden shears to perform clean cuts.
Make sure to always get rid of all dried leaves because these fungi overwinter on them.
Another tip is to keep your infected monstera away from other healthy plants, to prevent the disease from spreading further.
Pests
Monstera is very resistant to pests, but now and then, it just can’t defend itself against an army of six-legged, leaf-snacking insects.
I have some experience with spider mites and thrips, so I will describe my fight against them.
These pests bite your plant’s leaves and leave little, nasty, black dots behind.
At first, you may think that’s no big deal, but they will soon and quickly spread all over the plant and attack all other monsteras and evergreens you have.
Spider Mites
suck the sap out of the plant’s leaves. Over time, that sucked spot becomes dark yellow, brown, and eventually black. You can easily check for mites – just look under the leaf. If black dots are moving on the underside, chances are those are the pests you’re looking for.
Thrips
are small, leaf-sucking flies that sip all the moisture out of your monstera. Similar to mites, they too cause discoloration, which leads to black spots on the leaf’s surface.
Solutions
You can wash away the mites pretty easily with a water jet. Just make sure not to damage your plant. A shower in lukewarm water can also do the trick if there aren’t many spider soldiers. For thrips, I like to use neem oil.
It’s an organic oil made from compressed neem tree seeds. You can apply it in spray every couple of days, and the pests should be gone in less than a week.
Physical Damage
I like to fiddle around my plants to check if they have pests, diseases, or any anomalies in general. Sometimes, during these examinations, my clumsiness takes its toll and I end up ripping or twisting a piece of leaf. Another thing is, don’t put plants very close to each other.
That’s a big no-no in my experience. What happens is, when plants touch something else (be it another plant, a wall, a shelf…), they immediately think – this place is occupied. And unlike animals, they don’t think about turning back.
Being drama queens that they usually are, they just stop growing their leaves in that direction, acting as if this is the end of their world. Then, it’s the same as touching or twisting them.
They shut down their digestive system, called xylem, in those parts of the leaf which leave obnoxious black spots. Sometimes, the entire leaf can turn black for these reasons.
Solutions
Luckily, the solutions are really quick and easy. Stop touching your plants, especially young shoots and leaves. Only touch them when watering them, but try to avoid this too.
Get yourself a watering can for houseplants. And always make sure that they have enough space for growth. If you’re not sure how big of an area your plant might take up, do some beforehand research!
Should I Remove Leaves with Black Spots on Them?
This is not a simple question to answer. It mostly depends on the cause of these black spots. If the problem is caused by the environment, e.g. watering, temperature or humidity, you don’t have to trim the leaves unless they’re severely damaged.
When it comes to pests and especially diseases, cutting off diseased leaves usually does the trick to stop the spots from spreading further.
Final Words
There are many causes for your monstera turning black, and it’s important to get familiar with them. The more you learn about these problems, the easier it will be to face them when your plant gets sick. The most important piece of advice is to invest enough time in your monstera because it surely deserves every bit of it.
Sources: (University Blvd, Ames, IA, USA, Beijing Normal University)