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Calathea Root Rot (Signs, Causes, and Treatment)

I must confess that I am a calathea fan. I’ve had these dramatic beauties for years, and nothing threatens them more than root rot. Let me show you how to identify the source of the problem and save your calathea from root rot.

Root rot commonly occurs when you’ve overwatered your calathea. Rapid yellowing of leaves that droop or wilt is a surefire sign. Uproot your calathea for further inspection, then trim off decayed brown roots. Be sure to treat healthy roots with fungicide, then repot it afresh.

You’d be happy to know that it’s even easier to prevent root rot from affecting your calathea in the first place. You’ll find out more about this ahead.

Calathea Root Rot Symptoms

Calathea is a showy houseplant when it is in bloom. It will delight with dramatic leaves marbled with charming patterns. The stems appear to be robust and perky as well.

If root rot takes hold, things will quickly deteriorate. The rot disease ravages the roots quickly, so it’s best to act quickly. Don’t ignore  any of the following symptoms:

[1] Black and Mushy Roots

If you suspect your calathea has root rot, remove it from its pot. Aside from the soggy soil, you’ll find limp, spongy, or mushy roots. They appear darker brown or black.

The growing medium around the roots will also emit a sulfurous odor. With loose soil, decomposed roots may simply fall off. Healthy roots, however, are firm and white with a yellow tint.

Unfortunately, these root rot symptoms can be found beneath the soil line. As a result, your best bet is to watch for signs of overwatering. They frequently appear above the soil surface and early in the root rot progression.

 Calathea Black and Mushy Roots
Calathea Black and Mushy Roots

[2] Rapid Yellowing of Leaves

Fast-yellowing leaves are one of the first signs of root rot. Lower leaves near the soil are usually the first to turn yellow. The same is true for older foliage.

Yellowing indicates a lack of nutrients or water. As a result, calathea leaves may turn yellow if not exposed to enough light. It can also identify nutrient deficiencies, underwatering, cold drafts, pest infestations, and infections.

How can you tell if root rot is the cause? The yellowed leaves soon droop, wilt, or develop brown spots. Of course, the growing medium will be mushy or soggy.

Yellowing of Leaves Because of Root Rot
Yellowing of Leaves Because of Root Rot

[3] Swollen and Mushy Stem

Rot disease frequently begins at the root level before spreading to other areas. The stems closest to the soil are usually the first to be chopped. They will engorge excess water before rotting due to tissue damage and infection.

It is important to note that the presence of healthy stems does not imply that your calathea is free of root rot. However, mushy stems that appear droopy are a sign of advanced root rot.

If you don’t start saving your calathea immediately, the stems will collapse and your plant will die.

Keep in mind that stem rot is a symptom of root rot. Fungi usually cause this fungal disease from the Pythium, Fusarium, and Rhizoctonia genera. Look for classic signs such as squishy, soft, and enlarged stems.

Other symptoms include stem dieback, wilting, and weakening. On the lower part of the stems, black, brown, or reddish-gray spots may appear.

Swollen and Mushy Calathea Stem Due To Root Rot
Swollen and Mushy Calathea Stem Due To Root Rot

[4] Black Spots on Leaves

Black spots on the leaves are never a good sign. It indicates that the rot disease has spread to the leaves. They start out as small brown watery lesions.

These spots will continue to grow and darken as they spread. They will eventually merge to form large black blotches that will cause stunting.

This is because black spots and patches disrupt photosynthesis and weaken your calathea.

Balck Spots on Calathea Leaves
Balck Spots on Calathea Leaves

[5] Calathea Brown Leaves

Remember the yellowed leaves? As root rot damage progresses, they will begin to brown. Browning often starts at the leaf tips and edges.

Sometimes, you’ll notice brown spots or blotches on the foliage. Meanwhile, the entire leaf may turn brown before turning black and falling off.

Leaf browning can also be caused by dehydration, sunburn, cold injury, or fertilizer burn. When root rot is the cause, the browning leaves are almost always water-soaked and mushy to the touch.

Calathea Leaves Browning Due to Root Rot
Calathea Leaves Browning Due to Root Rot

[6] Calathea Plant Wilting

Calathea Plant Wilting
Calathea Plant Wilting

When my calathea begins to wilt, I usually inspect the soil. Because both underwatering and overwatering cause leaf wilting, this is a brilliant strategy. If your calathea’s leaves turn yellow and then wilt, there’s a good chance that it has root rot.

Calathea leaves that are wilting are usually limp or drooping. They will most likely feel soft or even mushy when you touch them. When it is thirsty, on the other hand, it becomes dry and crispy.

Wilting is frequently associated with other symptoms such as leaf yellowing, drooping, and curling.

[6] Stunted Growth

Another common root rot symptom is stunted growth. Almost unexpectedly, your calathea will stop growing. The amusing part is that stunted leaves rarely yellow.

Stunted leaves are smaller, curled up, and unhealthy-looking. The ability of your Calathea to absorb nutrients and water is hampered by root rot. As a result, it is malnourished and unable to produce new growth.

What Causes Calathea Root Rot?

[1] Overwatering

Root rot occurs when your calathea is left on “wet feet” for an extended period of time. The most obvious culprit is overwatering your calathea. It’s most likely to happen during the dormant winter season.

If too much water is in the growing medium, air will be sucked out. The roots will die and decay due to the lack of oxygen.

The moist soil also promotes fungus growth, which infects roots and causes them to rot and die.

Other potential symptoms of an overwatered calathea include:

  • Sudden yellowing of leaves
  • Stunted or slowed growth
  • Drooping leaves
  • Wilting foliage
  • Limp, swollen, or mushy stem

How to Fix

It would be best to fix root rot first. 

  1. Remove your calathea out of the pot for rot inspection
  2. Prune away affected roots, then treat the remaining ones with fungicide
  3. Repot using fresh peaty growing medium into a new sterilized pot
  4. Making sure the new pot has enough drainage holes is crucial.

It is crucial to keep the growing medium evenly moist but not soggy. That entails allowing the top two inches of soil to dry out entirely before re-irrigating.

Irrigation water should only be soft. That’s filtered, distilled, or rainwater, to name a few options.

[2] Poor Drainage

Calathea root rot is most likely caused by overwatering, but drainage problems can also contribute. Root rot can be seen from two different perspectives when it is caused by poor drainage in the soil.

For starters, it is possible that the growing medium is not well-drained and thus retains excessive water. This is more likely to occur if the soil contains a significant amount of organic matter or clay.

A poorly drained container, on the other hand, is a possibility. A plastic or clay pot will cause this to happen. A small number of bottom drain holes may be present or none at all.

This means that the growing medium will not drain properly in either situation. Aside from that, they don’t like to sit on wet, waterlogged, or otherwise squishy ground.

Excessive water drowns roots, causing them to wither and rot. 

How to Fix

First, you must identify what’s causing poor drainage. Is it the potting mix, pot, or both?

If it’s the growing mixture, repot using a lightweight peaty potting mix. I prefer using any potting mix (Amazon link) designed for African violets.

If it’s the container, switch to a good terracotta pot with at least two drainage holes.

[3] Fungal Infections

Root rot can also occur due to a fungal infection most commonly caused by soil-borne fungi. They are frequently spread through contaminated tools, potting mixes, or old containers.

Because of the overwatering, the fungus spores will germinate and infect the roots of your calathea. Not only does it cause the roots to rot, but it can also infect the stem and leaves of the plant.

Three different types of fungi cause calathea root rot.

Fungus NameSigns and Symptoms
Fusarium solaniFusarium solani is the rampant culprit for root rot in calathea. It’s often seen on plants propagated from cuttings. You’ll notice rapid yellowing and wilting of lower foliage. Other symptoms include stem dieback and browning of the vascular system.
PythiumPythium rot occurs in warm temps of roughly 70 °F (20°C. The fungus often infects weakened, diseased, or infested calatheas. Symptoms include bleached rotting roots, leaf drooping, wilting, and yellowing.
PhytophthoraPhytophthora fungus affects overwatered calatheas in cold environments. Phytophthora comes up to the base of the stem. Other signs include leaf wilting, curling, drooping, and loss of variegation.
(Source: University of Florida)

How to Fix

Controlling and managing fungal infections require a multi-approach strategy.

  • Remove and destroy infected leaves, stems, and other plant materials
  • Use an antifungal soil spray or drench treatment. For best results, I usually use sulfur or copper-based systemic fungicides. 
  • Repotting your calathea is crucial to eradicating the fungus

[4] Extra-Large/ Too Small Pot

Calathea roots require approximately one inch of soil. A plant in a pot that is too large for it will experience root rot because the growing medium will retain too much water.

Additionally, if the pot is too small for your calathea, the roots will be unable to get enough air circulation. In addition, the potting mix will dry out too quickly, causing damage to the roots.

Also possible is the accumulation of heat and fertilizer salts around the roots. Root rot will occur in both cases as a result of the damage.

How to Fix

Wrong size pot is a facilitator of root rot. So, pick out a container that isn’t too big or too small. The rule of thumb is to ensure an inch of the growing medium around the roots of your calathea.

[5] Low Temperatures and Cold Drafts

Occasionally, exposure to cold drafts or low temperatures can result in the development of calathea root. 

It’s important to remember that calatheas are not cold-tolerant plants. They will cause growth to be slowed and water to be accumulated in the soil. By continuing to water in the same manner, you only invite root rot to take hold.

How to Fix

You should trim off any foliage heavily damaged by cold injury

Your calathea won’t tolerate temperatures dipping below 61°F (16°C). Make sure your plant sits in a warmer setting in the 70-85 °F (20-29°C) range

Ensure your calathea isn’t exposed to cold drafts (open windows, doors, vents, etc.)

[6] Watering in Dormant Period

Calatheas flourish between March and October. When the winter arrives, the amount of sunlight drops, causing them to enter a dormancy period. It’ll experience slowed to no growth during this period.

Accordingly, you must withhold or reduce irrigation water. The excess moisture will build up in the soil and lead to root rot if you don’t.

How to Fix

Cut back on watering when your calathea enters dormancy during winter—only water your calathea when it appears wilted.

[7] Too Much Fertilizer

Excess fertilizer can also trigger root rot in calathea. This is especially true in winter when it has become dormant. The fertilizer will scorch the roots and encourage a fungal infection.

How to Fix

  • Treat your calathea to water-soluble houseplant fertilizer every month between March and October. Dilute the fertilizer to half the formulation recommended on the label.
  • Perk up the growing medium with some peat moss or compost fertilizer. This will add some organic richness.
  • During winter, you must stop fertilizing altogether.

How to Save Calathea from Root Rot 

You don’t need to be reminded that root rot can be fatal to your calathea. It cuts off the supply of nutrients and energy. With prompt action, you can rescue your calathea.

If you catch it early (before it destroys all roots), follow these steps to save your calathea:

1. Stop Watering

You must stop irrigating your calathea immediately. You’re only intensifying the problem.

2. Trim Off Infected Parts

Root rot spreads fast. It causes extensive damage to stems, leaves, and other parts. Take a closer look at your calathea from the bottom.

Snip away if you spot any diseased, dead, or infected parts. These include:

  • Heavily-browned leaves
  • Blackened leaves
  • Leaves speckled with brown or black spots
  • Completely yellowed foliage
  • Rotten or infected stems

You must remove and discard all infected plant materials. You aim to prune your calathea down to half its size. Don’t forget to sterilize the pruning shears after every trim using rubbing alcohol.

3. Unpot your Calathea

  • Take your calathea out of its pot for a thorough inspection of the root health.
  • Brush off some of the soil. 
  • If some growing medium remains, clean water rinses them off the roots.
  • Layer several magazines and use them to air out the root system. This will help them dry out quicker.

4. Trim Away Infected Roots

Trim all infected or dead roots at their edges. Use sterilized garden shears. Ensure to clean them up after every trim so you don’t transfer pathogens.

5. Repotting Your Calathea

Once you’ve cleaned up your calathea of the damage, it’s time to repot:

  • Use new terracotta or unglazed clay pot. Sanitize the pot by soaking it in a solution of water and bleach in the ratio of 10:1. Let it thoroughly dry.
  • Put a drainage layer on the pot’s bottom (I recommend using one)
  • Fill the pot halfway with the growing medium. Again, any potting mix meant for African violets will fit the bill. You can add some sphagnum peat moss.
  • Gently place your calathea
  • Fill the rest of the pot

6. Watering after Repotting 

Calathea potting mix should never be allowed to become completely dry out. Make sure the potting mix is evenly moistened.

Drizzle a small amount of water over your calathea to keep the growing medium slightly moist. It should never be allowed to become wet or sloppy.

Once you notice signs of new growth, make sure to thoroughly water the area.

7. Care After Repotting

Expect your calathea to experience some transplant shock after repotting. This should last a couple of days or longer, depending on the number of roots removed.

To help your calathea acclimatize faster:

  • Make sure potting mix is slightly moist
  • Give medium light
  • Ensure high humidity
  • Warmer temperatures above 65°F (18°C)

8. Propagating Calathea

If your calathea only has a few healthy roots left, propagating it may be your only option. For propagation, only healthy calathea plants should be used as sources of division. You have the option of propagating in either soil or water.

Organic and Chemical Treatment

Treating Root Rot With Chemical Fungicide

Treating calathea root rot with a chemical fungicide is not recommended as a first line of defense. Root rot can occur due to a fungus, to be sure. However, you will only know for certain after conducting a reliable fungus test.

If you must, copper-based fungicides can be used; mix two tablespoons of copper-based fungicide into a gallon of water for a drenching treatment.

Homemade Fungicide for Root Rot

I highly suggest using the following tried-and-true homemade antifungal remedies:

  • Charcoal
  • Cinnamon
  • Chamomile

All three are organic, and their antifungal properties last for many years.

How to Prevent and Control Calathea Root Rot

Avoid overwatering – To avoid waterlogging, water when one to two inches of growing medium feels slightly dry. It should never dry out completely. 

Using appropriate soil mix – Use peaty potting mix for calatheas. It should be airy, lightweight, and well-drained. Again, any African violet growing medium will do best.

Watering Schedule – Depending on location, you can water your calathea every five to fourteen days. Ensure the soil dries out a bit between watering. Reduce irrigation frequency drastically during winter.

Loosen soil – Work the soil to aerate the potting mix and help it dry out faster.

Ensuring care requirements – Give calathea filtered, indirect light, high humidity, and warmer temperatures of 70-85 °F (20-29°C).

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