Root rot is a common problem for houseplants, and Calathea root rot is no different. If not caught and treated in time, it will kill your Calathea. While some cases of root rot can be reversed, prevention is the best way to manage root rot.
Read the rest of this guide to learn all about the symptoms of Calathea roo rot, and the actionable steps you can take to reverse it.
The Calathea plant is a favorite for houseplant enthusiasts that tends to be fast-growing when given the right care.
It’s a beautiful plant with patterned leaves. However, the most interesting feature of the Calathea is the movement of its leaves. It is a part of the Marantaceae, or prayer plant family.
Each night, the Calathea folds its leaves, resembling hands folded in prayer. It does this through nodes known as pulvini. The plant adjusts the water pressure in the nodes, allowing the leaves to close and open.
What is Root Rot?
Root rot is typically caused by a bacterial or fungal infection or overwatering. Both infection and too much moisture essentially suffocate the roots, preventing them from getting oxygen.
Bacteria and fungi thrive in wet soil, so overwatering increases the chances of your plant developing them. If the Calatheas roots are in wet soil, this also blocks their ability to bring in oxygen.
Plants don’t breathe the same way we do, but they do require oxygen to survive just as humans do. Oxygen is essential for the plant to perform photosynthesis, the process that allows it to convert water and sunlight into food.
The roots require oxygen to produce a molecule used in photosynthesis. Without oxygen, the roots begin to die. If the roots die, the rest of the plant will soon follow.
Causes of Root Rot
Many plant lovers equate root rot to overwatering the plant. This can be the sole cause, but it’s far from the only culprit. The causes of root rot include overwatering, poor drainage, and underwatering.
As mentioned previously, overwatering can be the sole cause of root rot, because it prevents the roots from taking in oxygen.
Bigger isn’t always better. It may seem like a pot that’s larger than needed is a good idea. It provides your plant with more than enough room to grow.
However, this is problematic. Because the roots aren’t accessing all areas of the soil, parts of the soil are likely to remain wet. These damp undisturbed areas can cause root rot, even if the soil around your Calathea isn’t moist.
Low temperatures can also indirectly cause root rot. The Calathea will become dormant if the temperature is less than 60 degrees. Similar to a hibernating animal, the plant needs less water and nutrients during dormancy.
If you give your plant the same amount of water as in the summer, you will overwater it.
Overfertilization can also lead to root rot. Strong fertilizers can damage the Calatheas roots. If the roots are damaged, the plant can’t absorb the needed amount of water and nutrients. This reduces the overall health of the plant.
Because the Calathea can’t absorb the correct amount of water, the soil will remain moist. This can breed fungi.
A 10-10-10 fertilizer during the Calatheas grow season is all that’s needed for optimal growth. Do not fertilize the Calathea if it’s in a dormant period.
Poor drainage is closely related to overwatering, but they are separate issues. If you have poor drainage, you may be giving your Calathea the proper amount of water.
The problem is that the water gets trapped in the soil, allowing bacteria to grow.
Underwatering is the most surprising cause of root rot. You forget to water your plant. You notice your plant is very dry, and realize you’ve forgotten to water it.
To make up for the lack of water, you water your Calathea heavily. This can also lead to root rot.
When the roots don’t have access to water, they become dry and shrivelled. They are now in a fragile state. When you water them generously, it can shock the roots, leading to damage and root rot.
Signs of Root Rot
The signs of root rot can be divided into three categories. The first signs are those of early root rot. If the condition continues, the Calathea moves into the advanced root rot stage. If it’s not treated, it will enter the fatal root rot stage.
Early Root Rot
The signs of early root rot are similar to those of overwatering. These include yellowing leaves and slow or stunted growth.
It’s normal for your Calathea to become dormant in the winter. However, if it appears dormant during the growing season, this signifies a problem, as Calatheas are relatively fast-growing.
When stunted growth occurs, the Calathea will begin producing smaller or thinner leaves. It may also stop growing new leaves completely. You can expect a healthy Calathea to grow at least a few new leaves each month during the growing season.
Yellow and Wilting Leaves
Overwatering and root rot can cause yellow leaves. The leaves will yellow rapidly and become wilted.
The Calathea may appear to be dehydrated and begin to droop when it’s overwatered. In this case, the damaged roots can’t bring in water properly, even though water is available.
Advanced Root Rot
If you don’t recognize the signs of early root rot, it will continue. The signs of advanced root rot include a foul smell coming from the soil and black spots will begin to appear.
Foul Smelling Soil
The combination of standing water and rotting roots creates a sewage like smell. The fungi that cause root rot can also be the cause of the foul odor.
Generally, the worse the smell, the more damage to your Calathea’s roots.
Black Spots on Leaves
At this stage, the root’s inability to bring in nutrients will cause the cells to begin to die. The damage spreads from the roots into the leaves of the plant.
The leaves will develop black spots and droop. They may appear yellow around the black areas.
If you notice the signs of advanced root rot, you’ll need to check the roots of the Calathea. Healthy roots should be yellow and firm.
When root rot occurs, the roots become brown or black and mushy. Any rotted roots must be removed for the plant to survive.
Fatal Root Rot
If root rot isn’t treated, it will be fatal. The roots will continue to rot. Once there are no healthy roots to transport nutrients, the plant can no longer survive.
At this point, there is no way to save the Calathea. The one exception is the Calathea Marantas. This variety can be propagated via stem cuttings. All other varieties of Calathea must have healthy roots to propagate.
Treating Calathea Root Rot
To treat Calathea root rot, you’ll need to follow the steps listed below. This involves removing the Calathea from the pot, rinsing the roots, and removing any damaged roots.
Removing Your Calathea From the Pot
If you begin to notice signs of root rot in your Calathea, the best thing to do is inspect the plant. This requires removing it from the pot.
Removing a plant from its pot can be a bit traumatic for it, but it’s a much better alternative to allowing root rot to continue.
When removing the plant from the pot, don’t attempt to pull it by the stem. This will damage your Calathea. Instead, turn the plant upside down, placing one hand on the soil.
Shake it gently, and it should come loose from the pot.
Signs of Root Rot
Once your Calathea is free from the pot, you can inspect the roots for signs of root rot.
The most common and obvious sign of root rot is black or brown roots – no different to root rot in other plants such as the Majesty Palm. They will also be slimy and mushy. These roots will break easily. The stem may also be mushy.
The soil may be wet or waterlogged. The roots and the soil will have a foul smell, particularly in advanced or fatal root rot stages.
If some of the roots are still healthy, the Calathea can be saved. If all of the roots are black and mushy, the plant is unfortunately beyond saving.
Removing the Soil
If you discover root rot, the first step in treatment is to remove as much contaminated soil as possible with your fingers. Be as gentle as possible to avoid further root damage. However, you must remove all of the contaminated soil to prevent the bacteria from remaining.
Once you’ve removed the soil with your fingers, you’ll rinse the roots in water. Remove any remaining soil while rinsing. The rotted roots should come away easily during this process.
Once this process is complete, you’ll have a better idea of how far the root rot has progressed.
Removing Damaged Roots
The next step is to remove any remaining damaged roots. Using sterile scissors, cut away any black, brown, or mushy roots. If only part of a root is damaged, cut away an extra half an inch.
This ensures that you remove all of the infected roots. If all of the infected roots isn’t removed, the bacteria will continue to spread once the plant is repotted.
This is the same process as amputation. The goal is to remove any infected area, to stop the spread of the infection.
Disinfect Remaining Roots
Just as you would clean an injury to remove any harmful bacteria, you’ll need to disinfect the remaining roots. This prevents the bacteria from remaining on the roots and continuing root rot after your Calathea is repotted.
The best way to do this is with hydrogen peroxide. You’ll need to use 3% hydrogen peroxide, which can be found in the first aid aisle of many stores. Mix 1 part peroxide with 2 parts water.
If you don’t have peroxide, you can also use bleach. Use 4 to 6 drops of bleach with 1 quart of water. Concentrated bleach can cause further damage to the roots, so be careful not to overdo the bleach.
Dip the roots into the sterile solution. Then allow them to air dry.
Now you are ready to repot your Calathea. It’s preferable to use a new pot. If you must use the old pot, sterilize it well with bleach and allow it to dry.
You may need to downsize the pot, particularly if the Calathea had significant root loss. If the initial pot was too large, it’s essential to downsize.
Do not use the same soil or substrate, because it will contain the rot causing bacteria.
Be sure that the pot and soil are well-draining to prevent overwatering or waterlogging in the future.
Your plant has just been through a stressful situation and deprived of its proper nutrition. It’s tempting to fertilize your Calathea given these circumstances.
However, it’s better to avoid fertilizing immediately after repotting. When the soil doesn’t have a high nutrient level, the Calathea will divert its energy to root production.
This is a natural adaptation. In the wild, a plant will strengthen and stretch its roots when it needs more nutrients. This allows it to reach new soil, which provides the needed nutrients.
Your potted Calathea will have the same behavior naturally. Instead of devoting its energy to leaf production, as it would if the soil was nutrient-rich, it will strengthen its root system. This helps the plant recover from root rot.
After 6 to 8 weeks, the roots should be strong enough. At this point, you can add fertilizer, and allow your Calathea to produce new leaves.
It seems counterproductive, but you may need to remove some of the healthy leaves from your Calathea. When the roots are damaged, the plant won’t be able to get enough nutrients to sustain all its growth.
Removing some of the leaves will allow your plant to use its resources to support the remaining growth.
How many leaves you remove should correspond to how many roots was lost. If your Calathea lost 1/3 of its roots, you’ll need to remove 1/3 of the leaves as well.
This downsizing will give your Calathea a much better chance of surviving and becoming healthy.
Preventing Root Rot
Many cases of root rot can be cured, but it’s much better to prevent root rot from occurring in the first place.
You can do this by maintaining proper drainage, watering adequately, and using natural fungicides.
Proper drainage is essential for your Calatheas health. Be sure that the pot has drainage holes. If the pot doesn’t provide drainage holes, you can drill one or two holes into the bottom of the pot.
In addition to drainage holes, you’ll need to add a substance to aerate the soil. You can add perlite, pumice, or gravel to the soil. This will allow it to get air exposure and drain properly.
Remember, root rot bacteria thrive in an anaerobic environment. Proper airflow helps prevent root rot.
Using a natural fungicide can reduce the risk of root rot because it kills the bacteria that typically cause root rot. All you need to accomplish this is cinnamon.
Mix cinnamon into the soil when repotting. This will deter pests, act as a fungicide, and encourage root growth.
Adding a little peroxide to your watering can have a few benefits. It acts as an antibacterial and antifungal, which helps prevent root rot. Peroxide also increases oxygen.
When peroxide bubbles, it is actually oxygenating. This extra oxygen helps to prevent rot by increasing the oxygen within the soil.
You’ll need to water your Calathea properly to prevent overwatering. It generally requires watering once a week. You can also use the dryness test.
If the top 2 inches of the soil are dry, your Calathea needs to be watered.
Fertilizing your Calathea can help it grow to its full potential. However, over-fertilizing can cause root burn. Root burn will cause damage to the roots and prevent them from taking in water properly. This can lead to waterlogged soil because the roots can’t draw enough water from the soil.
You’ll need to fertilize the Calathea in the spring and summer months when it’s in its growth phase. Don’t fertilize it in the winter if it is in dormancy.
Saving Your Calathea From Root Rot
If your Calathea’s growth is stunted with yellow leaves, root rot is likely the culprit. When you remove it from its pot, a foul smell and black mushy roots are indications root rot has occurred.
To save your Calathea from root rot, you’ll need to remove any contaminated soil and damaged roots. However, the easiest way to save your Calathea is to prevent root rot in the first place.
You can do this by not overwatering and ensuring your Calathea has proper drainage. It’s also important to watch for the early signs of root rot.
The faster you catch and treat root rot, the better chance your plant will recover completely.