Black spots on your Monstera plant can cause you a lot of alarm. However, don’t panic. There are many different causes for black spots on a Monstera, and most of them are treatable, especially if caught early.
Your Monstera may have black spots due to root rot from overwatering, low humidity, sunburns, infection, nutrient deficiency, or cold temperatures. Fixes for black spots include drying out the roots, putting them in the shade, treating the infection, adding fertilizer, and warming them up.
In this article, I’ll discuss the different things that create black spots on Monsteras and what causes them. Then I’ll provide you with some solutions on how to fix and prevent these issues.
Root Rot From Overwatering
Overwatering is the most common reason Monsteras develop black or brown spots on their leaves. Even though Monstera is a tropical plant that loves lots of moisture, it is definitely possible to give it too much water.
Overwatering can also be caused by a lack of drainage in your plant’s pot or the fact that there is too much clay or organic matter in the soil, which will prevent water from draining.
At its worst, too much water can lead to root rot, a disease that attacks your plant’s roots in wet soil, which can be deadly for your plant. If it’s root rot that is affecting your Monstera, there will most likely be other signs of overwatering and lack of nutrients. These include:
- Yellow, wilting leaves
- Stagnant growth
- Soggy, smelly soil and roots.
If the roots are all dead and the stems are mushy, dark, and slimy, your Monstera is probably beyond saving. However, if it’s only the beginning signs of root rot, your Monstera may not be lost yet.
First, get rid of all the infected soil. This means taking your Monstera out of the pot and brushing away all the soil from the plant’s roots. Roots that are completely dead and infected will be brushed away with the soil.
Then, rinse all the roots with fresh water to make sure all the infected soil is completely gone.
After cleaning the roots, cut away the rest of the dead and infected ones with a cutting utensil such as a pruner. Make sure not to spread the infection to the healthy roots and disinfect your pruners after each cut with rubbing alcohol or diluted bleach.
Let your Monstera’s roots air dry, then report them in clean, well-draining soil. Make sure the soil is entirely new and the pot is disinfected.
After repotting, cut away about a third to half of your Monstera’s leaves. Since much of your plant’s roots are now gone, it will not be able to support as many leaves. Trying to do so will hamper its recovery time.
Place your Monstera in bright, indirect sunlight and let it dry out. Then continue to water it responsibly. Here’s a handy guide on how to best water a Monstera.
Monsteras need a good amount of humidity to thrive. As this is a tropical plant, air that is too dry is bound to cause some issues, one of which is dark or black spots. These spots will most likely be on the outer edges of the leaves and will seem brittle and crispy.
The humidity in the air needs to be above 40% to keep Monsteras happy, though they do best in humidity levels between 60-80%.
However, there’s another factor you’ll need to consider – humidity levels of more than 50% may do damage to your home.
There are several ways to increase the humidity in the air around your Monstera to get them healthy again.
A very simple way to add moisture back into the atmosphere is to place a dish of water near your plant/plants and let it evaporate into the air, creating more humidity.
The best way, however, would be to use a humidifier. This LEVOIT Humidifier from Amazon.com is a perfect choice. It has both warm and cool mist options and can humidify your plants continuously for up to 60 hours due to its 6-liter tank.
You can also purchase an enclosure for your Monsteras, such as a sealed greenhouse or a terrarium, to keep the humidity levels high without affecting the rest of your house. This Best Choice Indoor Mini Greenhouse from Amazon.com is a great option. It’s extra-wide and designed to maintain a perfect constant humidity to keep your plants happy while inside.
To measure the humidity in the air, you can use a hygrometer. I recommend the ThermoPro TP49 Digital Hygrometer (available on Amazon.com). It’s affordable and will tell you both the humidity and temperature in the room at all times. Place it near your Monsteras to make sure the humidity doesn’t fall below 40%.
Even though Monsteras are tropical and love sunlight, they can get burnt and begin to discolor if they get too much direct sunlight. This discoloration can come in the form of black or dark spots.
The too-hot rays of the sun can cause severe tissue damage on the leaves. This can also lead to holes, paling, and whiteness. The discoloration will also be very crispy, dry, and papery to the touch.
Sunburnt Monsteras can be saved easily. However, leaves that are too sun-damaged will have to be cut away, as they cannot be restored.
First, remove any seriously burnt leaves. Don’t worry – they will grow back green and healthy once you’ve treated the sunburn. After removing the burnt leaves, take your Monstera out of direct sunlight and place it in a shady, cool place.
Leave it there to rest and restore itself for a few days out of the light and heat. It will also want to cool down, so be sure to provide it with some form of cool ventilation. You can use a cool-mist humidifier to do this job as well.
Next, make sure it’s well-watered and moisturized – your plant will probably be parched from the harsh sun, so it will need the water. You should also consider misting it, as doing so will also help cool it down too.
In the future, make sure to keep your Monstera out of direct sunlight. Monsteras don’t like direct sunlight and should only be kept in indirect sunlight.
You can use fabric or sheer curtains placed over the window to diffuse the light your Monstera is getting. If your plants are outside, you can keep them beneath canopies, screens, or awnings to ensure they are away from the direct sunlight.
Fungal or Bacterial Infection
Fungal and bacterial infections are also able to cause black spots on your Monstera.
These spots will be relatively equal in size and be surrounded by a yellow halo.
Such infections thrive in warm, wet conditions and are most commonly caused by overwatering. They can also be caused by too much water on the leaves themselves due to excessive misting.
Damp leaves are highly susceptible to infection. Once the pathogen is on the leaf, it will multiply, leading to brown or black spots. Often, the spots will have a moist appearance.
Trim off and remove all infected leaves from the plant altogether, as they cannot be treated. Check to see if any other plants nearby have become infected because these infections are often contagious.
After removing the infected leaves, you may want to treat the rest of the plant with a bactericide for bacterial infections or a copper fungicide for fungal infections. Here is a quick guide to help you determine what kind of infection your Monstera may have.
Make sure to keep your Monsteras leaves dry to prevent infection or rot in the future.
If your Monstera is not getting the nutrients it requires, it may begin to show its stress through black or brown spots on its leaves. Other signs of nutrient deficiency will be stagnant growth and yellowing leaves.
Soil comes with nutrients mixed in. However, these nutrients get depleted over time, and your soil requires continual fertilization.
Fertilize your Monstera to make sure it is getting the nutrients it needs. Monsteras should be fertilized once a month with a balanced houseplant fertilizer diluted to quarter strength.
You can also nourish your Monstera with compost teas and rainwater, which has many benefits for plants that tap water can’t deliver. For an excellent compost tea recipe that you can easily make at home, check out this one by Eartheasy.
Monsteras need warmth to thrive and can’t tolerate temperatures lower than 55°F (10°C). If the temperature drops below that, the stress will show up in the form of black or brown spots.
The cold will also lower your plant’s immune system, leading to slower growth and a higher risk of infections. Sudden temperature drops may also damage your Monstera.
Warm your Monstera up! Monsteras do best in a place with a temperature between 60-80°F (15-26°C), and you’ll also need to ensure they get the right amount of heat at night when they’re out of the sun.
The area your plant is in will often be warm during the day, then drop below comfortable temperatures at night. This is especially true if your plant is outside your home, and you will need to make sure the temperature is warm and stable both night and day. This is where a sealed greenhouse or terrarium can come in handy.
Black spots on Monsteras are a symptom that something is wrong. Once you identify the cause, you can deal with it accordingly and prevent it from happening in the future.
Prevention is always the best solution. To prevent black spots, make sure to water your Monstera responsibly, nourish it well, and keep it at optimum temperature and humidity levels while ensuring it is out of direct sunlight.
- Monstera Plant Resource: How to Water a Monstera: The Ultimate Guide
- Monstera Guide: What Humidity is Needed for your Monstera?
- Cool Ray: Indoor Comfort Issues: Too Much Or Too Little Humidity?
- Wisconsin Horticulture: Split-leaf philodendron, Monstera deliciosa
- MSU: Signs and symptoms of plant disease: Is it fungal, viral or bacterial?
- Bonasila: 9 Benefits of Using Rainwater in an Indoor Garden
- Eartheasy: The Best Compost Tea Recipe
- Bloomscape: Monstera 101: How to Care for Monsteras