Monstera Black Spots

Monstera is a popular house plant grown in clusters of vines which give the plant a shrub-like appearance. The leaves are one of the plants’ main attractions, so it is worrying when they don’t look their best. One leaf problem you can come across is black spots, but the question is, why does your Monstera have black spots?

There are several reasons why your Monstera plant is developing black spots.  These reasons include over-watering, under-watering, sunburn, the cold, bacterial infections, fungal infections, and nutrient deficiencies. Luckily all of these problems have solutions.

As with all plants, Monstera can develop problems. Some of these present as black spots on the plant’s leaves. There are a few reasons why these black spots appear, so let’s look at these reasons and discuss how we can solve them.

What Causes Black Spots On Monstera?

There are seven main reasons as to why your Monstera has developed black spots:

  1. Over-watering
  2. Under-watering
  3. Bacterial Infections
  4. Fungal Infections
  5. Sunburn
  6. Low temperatures
  7. Nutrient Deficiencies

Black Spots On Your Monstera Due To Over-Watering

Monstera with black spots

One of the primary causes of black spots on your Monstera leaves is overwatering your plant. Many plant parents think they are doing their plants a favor by watering them often; unfortunately, this is not the case.

Many houseplants need to be watered once or twice a week if that. Overwatering your plant will lead to root rot. This can be fatal if left for too long and not appropriately treated.

Other signs of overwatering include:

  • Yellowing leaves
  • Wet, soggy soil
  • Soft, mushy stems
  • Drooping leaves

The Solution

So your Monstera has black spots on the leaves, and you want to see if overwatering is the cause. First, you need to check your soil. If it is very wet, hold off on watering your Monstera for a few days until the soil has dried out, then resume watering it only once a week.

You should also check to make sure your Monstera is not suffering from root rot. To diagnose root rot, you need to carefully remove your plant from its pot so that you can take a look at its roots.

Healthy roots have a whitish or light color, if on the other hand, your roots appear brown, black and sluggish, or slimy, you know that your plant is suffering from root rot due to overwatering.

If you discover root rot, you will need to carefully remove as many of the affected roots as possible with a pair of scissors. Clean the pot with soapy water and then refill it with fresh potting soil, adding a few handfuls of gravel or perlite to help with drainage. Your container needs to have adequate drainage holes to prevent waterlogging. Having good drainage is an essential factor in preventing root rot.

Remove the damaged leaves, replant your Monstera and place it in a room with bright, indirect sunlight and reduce your watering.

Read more: Monstera Care In Winter

Black Spots On Your Monstera Due To Under-Watering

If you notice that the black spots are accompanied by your Monstera’s leaves turning brown or getting crispy, this could signify that your Monstera might be suffering from under-watering.

The Solution

The primary solution here is to make sure that you water your Monstera often enough. Monsteras should be watered once every 1-2 weeks, making sure the top 2 – 3 inches of soil dries out between watering sessions. If your Monstera lives in a bright room, you will need to water it more often than while living in a room with lower light.

Black Spots On Your Monstera Due To Bacterial Infections

Bacterial leaf spot shows up as dark brown or black spots, surrounded by yellow halos on your Monstera’s leaves. These spots are often similar in size and, in many cases, exhibit sticky ooze.

These spots will often dry out and turn a brownish-red, with a sort of speckled appearance during dry conditions. In wet conditions, you might find that the spots grow larger and start to run together.

The Solution

If you have noticed that your Monstera is suffering from a bacterial infection, the following steps can help you to prevent the spread of the bacteria:

  • Remove the infected leaves slowly and over time, as removing too many leaves at once can place your plant under further stress
  • Try not to over-handle the diseased plant
  • Disinfect your scissors before and after each new cut
  • Avoid watering your plant from over the top of the plant as this can spread the disease
  • Ensure there is sufficient airflow around your plant
  • Avoid placing your plant in areas with low temperatures
  • Spray the infected areas on the plant with copper soap or,
  • Buy a chemical bacterial spray to treat your plant, and always follow the instructions on the packaging

Black Spots On Your Monstera Due To Fungal Infections

Many different kinds of fungi can cause black spots on your Monstera plants. These spots will present themselves as small brown spots with yellowish margins on the leaves, and they might develop as a concentric ring or a target pattern. Inside the brown spots, you will see black dots; these are the fruiting bodies of the fungus.

Sometimes these lesions or spots will run together, and the entire leaf will die. The fungus likes to feed on the dead and decaying plant matter that it finds in the soil.

The Solution

If you find that your Monstera plant is suffering from a fungal infection, prevent the spread of the fungus by following these steps:

  • Remove the infected leaves slowly and over time, as removing too many leaves at once can place your plant under further stress
  • Try not to over-handle the diseased plant and spread the infection
  • Disinfect your scissors before and after each new cut
  • Avoid watering your plant from over the top of the plant as this can spread the disease
  • Make sure you provide good airflow around the plant
  • Use a copper soap spray to treat infected areas and reduce future incidents, or
  • Apply chemical fungicides: the best would be chlorothalonil, tebuconazole, myclobutanil, or Bacillus amyloliquefaciens – make sure you follow the labeled instructions carefully and only apply after you have removed the infected leaves
Monstera plants

Black Spots On Your Monstera Due To Sun Burn

If you have placed your Monstera in an area where it receives direct sunlight and you notice that it has developed black spots on its leaves, these could be because of sunburn.

The Solution

Monstera prefers living in areas that receive good indirect light. The best practice is to keep your Monstera a few feet away from a window, providing it with good indirect sunlight without it being too harsh on the plant. If you notice that the leaves are still getting burnt, move the plant further away from the window.

If your Monstera is outside, it is best to place it under a porch or some form of shade cover to prevent leaf burn. Monstera can handle 3 – 6 hours of direct sunlight a day, but they would need to acclimatize to this sunlight over a few weeks.

Black Spots On Your Monstera Due To Cold

In some cases, your Monstera might develop black spots on the leaves during winter, or perhaps you have moved your plant to an area that is dark and doesn’t receive as much indirect sunlight. In these cases, the black spots developing on your leaves could be a result of the cold.

The Solution

In the winter, if temperatures in your area drop below 45 °F, it is best not to leave your Monstera outside as the cold air can cause the water in the pot to freeze, which will negatively affect the plant’s roots. Do not keep your plants out at night if temperatures drop below 45 °F.

If your plant is inside and in a dark corner and you notice black spots developing, it means that it needs to be in an area with better brighter indirect sunlight.

Users Also Read: Monstera Deliciosa Grow Light

Black Spots On Your Monstera Due To Nutrient Deficiencies

Black spots on your Monstera leaves can indicate that your plant is suffering from nutrient deficiency. Black spots or leaves turning black can indicate a manganese deficiency.

Other symptoms of nutrient deficiency include:

  • Yellowing leaves
  • Leaves not splitting

The Solution

You can give your plant a fertilizer boost about once a month during its growing season, spring to late summer. Do not use fertilizers with a high salt content as this can burn your Monstera.

Conclusion

There are several reasons why your Monstera could be developing black spots, and most of these problems have relatively easy solutions. When you notice that your leaves are developing black spots, the best thing to do is to check to see if you are over or under watering your plant. If this is not the problem, consider whether your plant has undergone changes or check for bacterial or fungal infections.

References

https://hgic.clemson.edu/factsheet/houseplant-diseases-disorders/

https://conservancy.umn.edu/bitstream/handle/11299/207208/MN2000_FSPP_030_revised1976.pdf?sequence=1

https://www.youtube.com/watch?v=hq2O1q_ciYs

http://www.ladybug.uconn.edu/FactSheets/monstera-deliciosa.php

https://gardening.stackexchange.com/questions/45521/monstera-swiss-cheese-plant-brown-patches-on-leaves

https://garden.org/thread/view/108474/Black-spots-on-my-monstera/

https://www.ehow.co.uk/facts_7884686_brown-spots-monstera-plant.html

https://www.reddit.com/r/plantclinic/comments/7qsone/monstera_deliciosa_with_blackbrown_spots/

https://www.thespruce.com/treating-brown-spots-on-leaves-5076039

https://www.houzz.com/discussions/5574535/monstera-black-spots-on-leaves