What Are Brown Spots On Calathea Leaves From?

Calathea leaves are stunning in their designs and colors, making the leaves a stunning foliage plant.

With these gorgeous leaves, one issue that could seriously affect it’s beauty would be the presence of spots that are brown.

Brown spots on leaves of Calathea could be the result of illnesses such as algal leaf spot septoria leaf spot, anthracnose. Environmental conditions that are poor like excessive light, low humidity and frost may cause the same problem. In some cases it is a pest infestation that is responsible for the brown spots.

In this piece I will discuss this specific issue and offer some suggestions for how to handle the issue.

Causes of Brown Spots on Calathea Leaves

The following is a discussion of the various possible causes for brown spots. In the majority of cases the signs may be similar.

This is the reason you need to pay attention to your calathea plants in order to determine what is the root cause for the spots that are brown.

Algal Leaf Spot

This is a form of illness that is brought on by organism that causes it, the parasitic algae Cephaleuros virescens.

It is not just affecting the leaves, but also the twigs that make up your Calathea. The spots appear like patches of green, gray or greenish-brown in color.

Calathea leaves could even turn yellow and fall in the early stages. This happens when the leaves become severely infected. (Source: Clemson University)

Calthea plant close up

Fungal Diseases

One reason that could be behind the brown spots that appear on your calathea could be due to an infection caused by fungi. Here are the most common fungal diseases that could infect the calathea plant:

  • Alternaria Leaf Spot

The cause of this disease is the fungus called Alternaria alternata. Calatheas with the disease will display tiny spots that are water-soaked in appearance. They appear like brownish red spots on the leaf’s surface.

  • Helminthosporium Leaf Spot

It is caused by Drechslera setariae This type of spot on the leaf triggers the leaves to develop lesions that are soaked with water.

The spots initially appear yellow, but they later change to brown. As time passes, the tiny spots merge and form larger marks on the leaves.

  • Fusarium Wilt

Calathea plants that are infected by fusarium wilt may display yellowing and wilting of leaf tips.

The reason for this is that the base of the plant from which it was cut, dies and begins to begins to rot. Fusarium Oxsporumis the pathogen that causes this disease.

Anthracnose

If you notice that leaves of the calathea are becoming yellow before turning tan and finally brown, it could be anthracnose, a type of disease.

The browning of the leaf tips spreads to the entire leaf until it completely disappears. Colletrotrichum as well as Gloeosporiumare two of the bacteria that cause this condition.

Plants that are injured are more vulnerable to anthracnose-causing fungi. If you’ve previously infected device, the likelihood to transmit the agent that causes disease is high.

Septoria Leaf Spot

Septoria leaf spot is often affecting the older and lower leaves of your calathea plant.

In general, leaves will appear to be brown or yellow. The affected leaves eventually wilt and eventually die.

If you pay attention, calathea leaves have tiny brown spots with an clear center.

Powdery Mildew

One thing you’ll notice when you have calathea leaves that are infected by powdery mildew is the appearance of a white powdered texture.

Sometimes the leaves will appear brown and have a papery appearance. This is due to the pathogen called Oidium species.

The pathogen could be transferred through decaying substances in soil to plants. They also can travel via the air.

Bacterial Leaf Spot of Calathea

Bacterial leaf spot on the calathea could be caused by P. Cichorii, as well as Pseudomonas sp. The bacteria infect the leaves of certain species like C. roseo-picta, Vandenheckei’, and C. roseo-lineata.

The lesions appear to be water-soaked with a brown to tan color and can be as large of 1 inch in diameter.

The signs of Pseudomonas species. are usually observed in leaves that are younger. The P. Cichorii is a problem for the older leaves of the calathea. They are more likely to grow in the event of a prolonged wet season.

Nutrient Deficiency

In the absence of any vital nutrients causes leaves to show signs of chlorosis or necrosis.

The leaves of necrotic or chlorotic initially appear yellow, while other have brown edges.

The signs and symptoms will be based on the macronutrient or micronutrient that is insufficient.

  • Mobile nutrients like nitrogen (N) and the phosphorus (P) and potassium (K), as well as magnesium (Mg) manifest their symptoms on the older and lower leaves.
  • However, there are immobile minerals such as calcium (Ca) and Boron (B) and chlorine (Cl) and cobalt (Co) and copper (Cu) and iron (Fe), manganese (Mn), molybdenum (Mo) as well as silicon (Si) and sulfur (S) and zinc (Zn) are all symptomatic on younger leaves.

Edema

Edema is a physiological reaction that plants experience to environmental conditions.

It’s caused by inequal water relations within the plant. In the end, specific plant parts like stems, leaves, and petioles grow protrusions.

The affected parts will have the appearance of a blister on their surface. The blisters break and grow into brown lesions later on.

Excess Light or Leaf Scorching

Calathea requires moderate exposure to light. Low light levels could cause the leaves to become limp and pale.

However excessive light can cause the tip becoming necrotic and may even cause bleaching. The higher levels of light could cause tissue damage to your calathea.

Then, it leaves brown marks across the surfaces of the leaves due to the scorching. The color also fades as the leaves undergo bleaching.

Frost Damage

A temperature range from 65degF to the 80th degree (15degC up to 27 degrees Celsius) is perfect for indoor calatheas.

In general, they’re not fond of temperatures that are cold. Therefore, they are easily damaged by frost.

If the temperature is far too frigid for the calathea, tissues may be able to freeze and die.

After thawing, you’ll see brown spots appear on the leaves. The damage caused by frost on the leaves of calathea is irreparable.

Low Humidity

The calathea plant definitely loves the extra moisture within the atmosphere. It therefore requires an extremely humid environment for it to flourish.

It needs around 40% – 60 percent relative humidity in order to grow and produce beautiful leaves. If the air is dry, the Calathea leaves can easily get brown edges.

Insect Infestation

Pests such as caterpillars, mites, scales and mealy bugs typically affect ornamental plants such as the calathea.

They typically feed on leaves, puncturing tissues and sucking up the contents. The wounds are left to grow to form brown spots.

The presence of insects in small amounts isn’t an issue that is serious. However, if they increase in number and overtake your garden, it will certainly cause you to be stressed. Don’t be afraid of the pests that appear.

Watering Problems

Because calatheas only requires moderate watering, there is always the possibility of overwatering or submerge the plant.

Incorrect watering can cause the plant to become dehydrated or even drown. In both instances the plant suffers from stress caused by water and shows signs of the signs of browning or yellowing in leaves.

The overwatering of roots can cause rot. The roots can shrink when water is not drained because of the dehydration.

In the end that the roots will face difficulties transporting nutrients and water out of the soil the other parts of the plant.

Fertilizer Burn

One of the effects caused by fertilizers that are too much can be the burning the leaves’ tips or the burning of leaves.

It is common to see brown tips appearing around edge of your calathea leaf.

The soluble salts of fertilizers that are too numerous cause an arid condition on the soil, by taking water away from the soil’s roots.

Insufficient soil moisture causes the soil becoming wilted. Sometimes the contact with fertilizer can cause burning.

This could happen if the solution isn’t diluted to one-quarter or half of the initial recommendation.

How to Treat Brown Spots on Calathea Leaves?

When you’re certain of the root of those brown marks on the calathea, it’s time for you to act.

Here are some simple solutions we suggest to treat the brown spots that appear on your calathea:

For brown spots caused by diseases (Bacterial, Fungal, etc.)

  • Get rid of infected plants and parts. Remove them from the plant to prevent spreading of disease.
  • Place the calathea in an air-tight, dry and well-ventilated area.
  • Do not water the plants from above. Make sure the foliage is dry for as long as is possible. The damp conditions encourage the growth and spread of pathogens.
  • Use the appropriate chemical, such as the fungicides (link on Amazon) in accordance with the agent responsible for the illness.
  • Remove plants that are heavily infected. If the disease continues to persist even after implementing the above-mentioned treatment methods, it’s time to let go of your calathea plants.

For Brown Spots Caused by Nutrient Deficiency

  1. Determine which specific nutrients are not being utilized by exposing the soil to an analysis. It is possible to send samples to a lab. But, it can be quite expensive, especially when you’re only worried about a couple of pots of calathea plants.
  1. Talk to an expert in ornamental plants. If you have a horticulturist friend you should ask them to examine your plant. They are definitely better at recognizing nutritional deficiencies.
  1. Examine the pH of the soil and adjust it according to the soil’s pH. One reason that nutrients are inaccessible to plants is because the soil’s pH isn’t at its ideal level. In order to be able to grow calathea, the soil’s pH should be between 6 and 7. It is possible to test this with the pH tester. (link to Amazon)
  1. Repot with a healthy and fertile soil. Maybe the potting medium of your calathea has already exhausted. If that is the situation, you must move it to a different pot with a new set of soil.

For Brown Spots Caused by Edema and Watering Problems

  • Your calathea should be watered with moderate amounts of water. Keep in mind that your plant is not an over-weight or a weak water-user. It requires just enough water to flourish.
  • Make sure that the water excess go out of the pot to prevent root rot. Make sure that the pot has drainage holes that are large enough. Let the water drain before placing it back into the original place.
  • Alter the frequency of watering based on the season. If temperatures rise then increase the frequency of watering. Don’t do this if it becomes colder.
  • Do not water during the evening. The calathea’s calathea can hold water longer since transpiration slows in the evening. Instead, you should water in the early morning.
  • Make sure your plant receives sufficient light. The sun emits heat, and this can increase the rate of transpiration. Therefore, your plant is likely to shed water

For Brown Spots Caused by Low Humidity

  • Set your calathea in an area with high humidity. It is a good idea to include your kitchen as well as your bathroom.
  • Make sure to mist your calathea regularly whenever the air becomes too dry. Make use of a spray bottle to mist the foliage each morning. It is possible to do this at least once per day if the humidity is too low.
  • Make sure you have a humidifier you have one. In the event that you do not have the time to mist and swabbing, let the humidifier do the job for you. However, this could result in extra costs for you.
  • Combine the plants together. Plants that are together are more beneficial because the water they release is absorbed by the other.
  • Make use of a tray for water. This is especially useful if you’re planning to leave your home for a few days or even weeks. Let your calathea sit on a tray made of pebbles that’s filled to the half with water.
  • Make use of the bell-shaped dome to hold in moisture. There are many gardeners who use this method. It is similar to the atmosphere of the terrarium garden, where humidity is kept high through the glass container that surrounds it.
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For Brown Spots Caused by Frost Damage

  • Move your plant’s calathea to an area that is warmer during the night. The temperatures at night are typically lower, and this can cause frost to develop.
  • Make sure to cover your calathea with insulation when temperatures drop. In winter, be sure that you protect your calathea with an additional source of warmth around it. Cotton sheets are ideal to protect your calathea from the chill.
  • Reduce the amount of water you use when the temperature begins to fall. In excess moisture can cause the soil in the potting area to become frozen. Do not water the garden in the evening.
  • Make sure you have sufficient lighting sources. Check that your calathea is getting enough light, especially in cold weather. Include artificial light sources if required.

For Brown Spots Caused by Excess Light/Scorching

  • Limit the exposure of your calathea plant directly to sunlight for around 2-6 hours per day. If the light intensity is too intense limit exposure to the minimum.
  • Include additional shades like sheer curtains that protect you from the harsh light intensity. Do not let your calathea directly contact the glass of your window.
    • Move your calathea into an area where the light intensity isn’t as strong and destructive.

If you are using artificial light sources ensure that they are at a distance of at least 12 inches of your calathea.

For Brown Spots Caused by Fertilizer Burn

  • Remove excess fertilizer using water. Sprinkle water on the soil over and over till the crust of white has disappeared. Give between 1 and 2 hours between each watering to avoid damaging the roots.
  • Stop fertilizer applications until roots are able to recover. Give your calathea the time it requires.
  • Repot the Calathea. If the build-up of salt is already excessive, it is better to remove the soil in the potting pot to replace with a fresh one. Make sure to use a fertile potting medium to make sure that all the essential nutrients are in place.
  • Utilize fertilizers that slow release. The reason fertilizer burn occurs is because we tend to utilize fertilizers that are readily available. While they can have a quick impact, they could cause damage to the plant when not properly handled.
  • It is better to fertilize the soil and not the leaves. Contact with fertilizer solutions could easily cause burning of the leaves or any other plant. Do not do it unless your fertilizer is designed to be applied to the leaves.

For Brown Spots Caused by Insect Infestation

  • Remove the pests manually. It’s possible to get them before they’re gone when you’re diligent about monitoring them frequently.
  • Spray water on areas in which the colonies of pests have risen. A little pressure is enough to keep insects from the leaves and stems.
  • Take away the heavily infected leaves. In the event that damage to your plant is extensive it is better to trim that area. This will stop the insects from spreading.
  • Use homemade solutions out of diluted horticultural oils and dishwashing/insecticidal soap to kill the insects. Make this a habit whenever you notice insects swarming around your calathea.
  • In most cases there’s no need for chemicals. However, in the event of a need you need to, use natural and eco-friendly products.

The treatment of brown spots in the calathea isn’t a single-time task. It is important to remain patient when applying the remedies repeatedly until you get positive results.

There will be times where you’ll need to test with yourself to discover an effective method to control your calacthea.

How to Prevent Brown Spots on Calathea Leaves?

Naturally brown spots won’t show up on your calathea if conscious of providing the ideal conditions for growth from the start.

Here are a few suggestions to avoid the occurrence in brown marks on your favorite Calatheas.

  • Begin with a healthy and vigorous Calathea plant. Always select the most attractive plant wherever you go and purchase it from garden shops. Don’t ever purchase plants that are unhealthy or diseased.
  • Utilize potting mixes that have been sterilized. This will reduce the risk of developing soil-borne illnesses. Pathogens can remain alive in soil for a long period of time, so heating the soil will eliminate them.
  • Make sure to use that you use the correctr mixing of potting mix. (Link for Amazon) Plant the Calathea in a draining potter’s medium that is rich in organic matter. Utilize pine bark, peat or vermiculite as well as perlite to enrich soil.
  • Make sure that the pot you choose to use is appropriate in dimension and that has a good drainage. Small or over-sized pots could cause problems with watering. If there isn’t any drainage it is a good likelihood that root rot could occur.
  • Make sure the foliage is dry. Keep in mind that a damp and humid environment is extremely favorable for pathogens to thrive and expand.
  • Find the most suitable place. It must be one that gets sufficient light and has high humidity and is warm at night. Be sure to keep your calathea out of cold and drafty areas.
  • Control your watering. Don’t overdo it, but don’t too little. This is the rule for the calathea. Examine the condition of the soil prior to irrigation. Let the two inches of the soil to dry first.
  • Always dilute fertilizers. Calatheas have a low tolerance to salts. They are prone to developing fertilizer burns, so be cautious when applying fertilizer.
  • Be aware of temperature fluctuations. If it drops below 60 degreesF (15 oC) Be ready to shield your Calathea from frost. Install insulation prior to it’s time.
  • Don’t be afraid to get rid of any calatheas already in poor condition. Sometimes, getting rid of them is the most effective way to preserve the remaining plants. This is especially true when dealing with plants that are sick.
  • Check your calathea regularly. Treat them as if they were your children. This gives you the opportunity to identify any issue before it escalates into something serious.
  • Make sure to check your plant prior to taking it into your home. The outdoor movement of your calathea can be beneficial for the plant. However, ensure that you inspect them for the signs of pests prior to you bring them back inside.
  • Maintain the changing conditions in the best shape as you can. There are certain changes in the world which we cannot manage. As a plant-parent you are responsible to discover ways to keep your calathea as secure as possible.

Final Words

In general, caring for the calathea plant requires more effort than with others indoor plant species. It is thought of as an extremely maintenance-intensive houseplant. It is a good idea to not delay when it comes to caring for the Calathea.

However, what it needs for maintenance and care is compensated by its beautiful appearance. You can give the calathea everything it requires and it will never disappoint. The beautiful leaves will display is your most prized possession.

Stephanie

Stephanie

Went from a bad gardener to a half-decent one over 10+ years. Super happy to share my tips and tricks with you :)