Calatheas are not difficult plants to care for, and typically have the same growing requirements as most other tropical houseplants. That doesn’t mean, however, that they won’t experience any problems.
For example, when your Calathea has brown spots, it is usually a sign that something is seriously wrong with the plant and needs your assistance ASAP.
Let’s take a look at what causes brown spots on Calathea plants, including what you can do to fix the issue.
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What causes brown spots on Calathea?
The most common causes of brown spots on Calathea are overwatering, bad water quality, excessive sun, diseases and pest problems. Thankfully, once you have determined the actual cause, you can take the necessary steps to correct the issue.
1. Overwatering
Overwatering is one of the leading culprits when the Calathea has brown spots. The issue of overwatering isn’t something to fool around with, since it makes the roots soggy, which leads to root rot.
In fact, seeing brown spots on Calathea is an advanced sign of root rot and, at this stage, trying to save the plant can unfortunately often be a waste of time and resources.
2. The soil is too compact
Along with simply giving the plant too much water, overwatering can also occur if the soil you are growing the Calathea in is too compact. Calatheas need soil that is light and airy, allowing the water to drain through it.
A good general soil mixture for Calathea consists of 50 percent potting soil, 20 percent charcoal, 20 percent orchid bark, and 10 percent perlite.
If you don’t want to create your own mixture, you can purchase a commercially available potting mix designed for Calathea.
3. Excessive amount of sunlight
When the Calathea has brown spots, it may be because the plant is getting too much sun. Excessive sunlight not only results in brown spots appearing on the leaves, but it also burns and scorches the foliage.
If the excessive sun continues, the overall growth rate of the Calathea will suffer.
4. Conditions are too dry
Calatheas are tropical houseplants that prefer a humidity level a bit higher, about 50 %, than your home’s average humidity. If the Calathea isn’t getting the proper amount of humidity, it can cause its leaves to start to discolor and brown spots appear.
If the humidity issue isn’t fixed, the leaves will begin to dry out and become crispy, the plant’s growth will slow, and it can become stressed. A stressed Calathea is more susceptible to pest and disease problems.
5. Overfertilizing
Overfeeding is another potential reason as to why your Calathea has brown spots. Calatheas aren’t heavy feeders and the chances of a Calathea’s health suffering from not feeding is much lower than the chances of overfeeding the plant.
If you do decide to feed the Calathea, make sure to use a balanced liquid fertilizer, and apply it at 1/2 its strength no more than once a month during the spring and summer.
6. Poor air circulation
When water drops come in contact with the leaves, they usually air dry in a matter of hours, if not less.
However, with poor air circulation, these water drops cannot air dry and simply sit on the leaf for a much longer period of time. This will result in brown spots forming on the leaf where the water drop sat.
Additionally, proper air circulation is vital if you mist your Calathea. So keep that in mind before you dampen the plant’s leaves.
7. Leaf spot disease
There are a few different diseases responsible for a Calathea having brown spots, but leaf spot disease is one of the most common ones. Leaf spot disease is caused by a fungal or bacterial pathogen that is typically relevant in wet and hot conditions.
This disease can be hard to treat and hard to get rid of, so preventive measures are the best option for protecting the Calathea from these diseases.
8. Pests
Even though Calatheas are not overly susceptible to pest infestations, they are not immune to them and can sometimes come under attack.
In most cases, however, the problem is usually more of an annoyance than a serious issue. Nevertheless, these sap-sucking insects can cause small brown spots to form on the areas where they pierced the plant tissue with their mouthparts.
Related: 9 Proven Steps to Treat a Calathea With Spider Mites
9. Cold temperatures
When a Calathea has brown spots, it could be because the temperature is too cold for this tropical plant. Calatheas need temperatures that fall between 68 and 85 degrees.
If the temps are too cold, especially if they are under 60 degrees, brown spots can start to form on the plant’s foliage.
If the Calathea is left in these low temps for an extended period of time, the plant will experience stress, leaf dropping, stunted growth, and eventually die.
10. Subpar water quality
The type of water you use to hydrate the Calathea can have a direct effect on its health, and can even cause brown spots to form.
In most cases, you can point the finger at tap water, since it typically contains chlorine, fluoride, and other additives that cities add.
11. Not enough light
Low light conditions could potentially be the cause when the Calathea has brown spots. However, this isn’t nearly as common of a reason as too much sun.
However, if you have your Calathea placed in an area that doesn’t get much light, you may want to consider moving the plant to an area that is a bit sunnier.
Related: Calathea Light Requirements: The Ultimate Guide
12. Underwatering
Not giving the Calathea enough water can also cause the leaves to develop brown spots. Calatheas do like their soil to stay moist, but not soggy, and not giving them enough water can cause their leaves to start drying out.
As the underwatering continues, the leaves will start to feel dry and crispy, brown spots can form, and the plant’s health and growth will suffer.
How do you treat brown spots on Calathea?
Treating brown spots on Calathea can be difficult, especially if you’re not sure what is causing the problem. In order to properly treat the issue, you must first determine the cause and then take the appropriate action to save your Calathea.
1. Immediately stop overwatering the Calathea
If the brown spots are caused by watering the Calathea too much, you will need to immediately stop watering the plant and allow the soil to dry out before watering again.
The easiest way to determine whether or not overwatering is the problem is to look at the soil in the pot. If the soil is soggy, you know the plant is overwatered.
If, however, the soil is dry and pulling away from the sides of the plant, your problem is not enough water.
2. Increase the humidity level
Low humidity levels are another reason as to why the Calathea has brown spots.
Sitting the Calathea plant on a drop tray or placing a humidifier next to the plant will go a long way to increasing the humidity to a level that is more suitable for this tropical plant.
3. Treat the Calathea with fungicides
Fungicides are useful tools that help treat a wide array of problems caused by fungal pathogens. Unfortunately, many of the pathogens that cause leaf spots are not effectively controlled with fungicides alone.
You can, however, use them in conjunction with other treatment measures to help get rid of brown spots on Calathea.
When using fungicides, always read and follow the instructions printed on the back of the bottle. Additionally, select a fungicide that has leaf spots listed on its label as one of the issues that it controls.
Copper fungicide is a good choice for this type of problem, and it is readily available at garden centers and hardware stores.
4. Keep leaf litter to a minimum
Leaf litter may not seem like a problem, but it is essentially an open invitation to pests and diseases.
Allowing fallen leaves, or other plant matter, to sit on the soil surface will increase the chance of fungal pathogens or sap-sucking insects attacking the Calathea.
Simply picking up any fallen plant matter from around the Calathea will go a long way to keeping the plant healthy, while also preventing potential problems.
5. Prune off infected leaves
If there are only a few leaves that have brown spots, you may be able to control the problem by pruning them off the plant.
Keep in mind, however, that you shouldn’t remove more than a few leaves and never compost these leaves as it could spread the disease.
Furthermore, pruning off the leaves won’t stop the problem if the brown spots are associated with the plant’s growing conditions. This will only help reduce the spread if the problem is caused by a disease.
6. Water at the base of the plant
Leaf spot disease is another potential cause when the Calathea has brown spots, and it is caused by a pathogen that can lurk in your plant’s soil. Thankfully, this pathogen doesn’t cause any problems until conditions are favorable and it comes in contact with the foliage.
In most cases, contact occurs when you water the plant from above, since this causes soil to splash up on the leaves. By watering at the base of the plant instead, you will help reduce the chance of splashing the pathogen-filled soil onto the Calathea’s leaves.
You may also be interested in: How Often to Water Calathea Plants (So They Thrive)
7. Repot the Calathea
Repotting Calatheas is not usually recommended unless the plant has outgrown its current container. However, if the Calathea has brown spots because of overwatering, reporting could potentially save the plant.
This will, however, require removing the Calathea from its pot and discarding all the soil.
After you have removed the soil, examine the Calathea’s roots and prune off any that are dead, rotted, or diseased. Then repot the Calathea in a clean, sterilized container with fresh soil.
You will need to water the Calathea once it has been repotted, but then refrain from watering again until the soil begins to dry out.
8. Treat the Calathea with horticultural oil
If your Calathea has brown spots because of a pest infestation, you will need to liberally apply a pesticide to the underside and topside of the leaves.
Horticultural oil is typically the go-to pesticide because it is much safer than other options, and can be used around people and pets.
In most cases, you will need to apply the horticultural oil once every 10 to 14 days to control the pests. However, this can vary depending on the brand used. For the best results, follow the instructions listed on the bottle.
9. Flush the soil to remove excess minerals.
When the Calathea has brown spots caused by overfertilization, you will need to flush out the excess minerals that have built up in the soil.
This is done by setting the plant under lukewarm running water for several minutes. You may have to do this a few times to get all the excess minerals out of the soil.
It also goes without saying that you should immediately stop fertilizing the Calathea, and then don’t fertilize the plant again for a while. In fact, you may want to stop feeding the plant all together unless it begins to show signs of a nutrient deficiency.
If you’re not sure whether or not this is the cause of the brown spots on Calathea, take a look at the top of the soil. Do you see a whitish or grayish substance on the top of the soil? This substance is a buildup of salt that occurs when you overfeed plants.
How to prevent a Calathea having brown spots
It is always best to prevent your Calathea from getting brown spots in the first place. Preventing brown spots on Calathea is actually fairly easy since it usually revolves around ensuring the plant has its ideal growing conditions.
1. Don’t overwater the Calathea
Since overwatering the Calathea is the leading cause of brown spots on the plant’s leaves, it’s safe to assume that you can prevent this problem by simply not overwatering it.
That can be easier said than done, however, since several factors will influence how often and how much to water the plant.
A good general rule of thumb is to water the Calathea once a week during its active growing season and then reduce it to about once every 10 days during the winter season.
2. Avoid growing the Calathea in compact soil
Overwatering isn’t just caused by hydrating it too much – it can also occur if you grow the Calathea in soil that doesn’t promote drainage.
That is why it is important to avoid compact, heavy soils, such as clay-based, and instead use soil that is light and airy.
Related: Best Calathea Soil: Tips to Pick the Right Potting Mix
3. Provide bright yet indirect sunlight
Calatheas don’t do well in direct sunlight, but they do need at least 6 to 8 hours of indirect sun every single day. A good indoor location for Calatheas is one near a bright window, such as one that faces east.
Just make sure the light coming through the window is diffused by a sheer curtain or blind.
Keeping the Calathea out of direct sunlight at all times is the safest route to avoid potential problems. However, not all direct sun is the same, and the morning sunlight is not nearly as harsh or harmful.
That means you can place the Calathea in an area where it receives direct morning sun, as long as it is kept out of direct sunlight for the remainder of the day.
4. Don’t overfeed the Calathea
As stated above, you are more likely to overfeed the Calathea than the plant is to experience problems associated with not fertilizing. This is because Calatheas are not heavy feeders.
If you must feed the plant, consider using a more organic option, such as worm castings or compost.
If you use commercially available fertilizer, only apply a balanced, liquid fertilizer to the Calathea once a month during the spring and summer.
You can also help reduce the chance of overfeeding the Calathea by reducing the amount of fertilizer you give the plant by 1/2 of its strength.
Related: Best Calathea Fertilizer for Prayer Plants (+ When to Do It)
5. Increase the amount of humidity in the room
Because Calatheas are tropical plants, they need humidity levels that are a little higher than what your home’s average humidity typically is. Thankfully, you can easily increase this level by utilizing a humidifier or drip tray to put moisture into the air.
When conditions are extremely dry, consider misting the Calathea to help keep the leaves moist, while also increasing the humidity level.
6. Make sure the Calathea is growing in the correct temperature.
Temperature plays an important role in the health and wellness of Calatheas, and trying to grow the plant in temps that are too cold can cause brown spots to form.
That’s why it is important to ensure Calathea is in an area where the temperatures are 68 to 85 degrees consistently throughout the year.
Additionally, make sure to keep the Calathea away from areas where temps go up and down drastically, such as near an exterior door or next to a heating or cooling vent.
7. Use distilled water to hydrate your plant
Calatheas are sensitive to the additives, such as chlorine, often found in tap water. Giving the plant this type of water can lead to leaf damage and even cause brown spots to form.
The best type of water for Calatheas is distilled water, although you can also use filtered or rain water.
If you must use tap water, let the water sit out for about 24 hours before watering the Calathea. This will give any chlorine in the water enough time to dissipate.
10. Don’t forget to water the Calathea
Calatheas are a houseplant that likes its soil to stay moist but not soggy. However, trying to find the right balance to avoid over or under watering the plant can be difficult.
A nifty little trick to ensure you only water the plant when it needs it is to feel how dry or soggy the soil is before watering.
If the first 2 inches of soil still feel moist, then you can wait a day or two before testing it again. You should only water the Calathea once the soil starts to feel dry.
11. Implement proper care on an ongoing basis
Probably the best way to keep brown spots on Calathea at bay is to ensure the plant is getting the proper care.
This means growing the plant in the right soil, lighting, humidity level, and temperature, while also providing it with the proper amount of watering and feeding.
Proper care also involves being on the lookout for potential pests, diseases, and other problems before they get too bad.
Why does my Calathea have brown edges?
Brown edges on your Calathea leaves are generally a sign that the plant isn’t getting enough water. It could also signal that the air is too dry. No matter what, you will need to increase the amount of watering you give the plant, while also upping the humidity level.
If you want to confirm that underwatering is the cause of the brown edges, simply take a look at Calathea’s soil. Is it dry and pulling away from the pot? If so, then that is your confirmation that the plant is too dry.
A good general rule of thumb is to water the Calathea once a week during the spring and summer, and ensure the humidity level is at least 50 percent throughout the entire year.
Will brown spots on Calathea go away?
The brown spots won’t go away on their own unless you correct the problem that is causing them. In most cases, the problem is associated with poor growing conditions or neglect. Thankfully, these issues can typically be corrected rather easily.
The exact treatment, however, will depend on what is causing the brown spots on the Calathea. Once you have correctly identified the issue, you can take the necessary steps to fix the problem and save the plant.
Can a Calathea recover from brown spots?
Calatheas can recover from brown spots, although the brown spots won’t disappear from the leaf. Once a leaf has developed brown spots, the spots are there to stay. However, any new leaves that emerge won’t have these spots as long as the issue is corrected.
Once you have the issue causing the brown spots on Calathea identified and corrected, the plant should make a full recovery. This can, however, take several months.
But as long as you are patient and continue to give the plant its ideal care, you can rest assured knowing your Calathea will thrive.
Should I cut off Calathea leaves with brown spots?
You can cut off the Calathea leaves with brown spots, but remember that over pruning can cause more harm than good. If the brown spots are only on a few leaves though, then snipping them off probably won’t cause any issues.
If, however, there is an abundance of infected leaves, removing them all can cause the plant’s growth and health to suffer.
You should never prune more than 1/4 of the plant’s leaves as the Calathea does need its leaves to absorb nutrients from the sun.
Additionally, you should only prune the Calathea during the spring or summer when it is actively growing and make sure to water the plant thoroughly beforehand.
All these preventive measures are done to help reduce stress that can occur when pruning any plant. Once you are done pruning, clean and sanitize the pruning shears to avoid spreading pathogens to other plants.