Why is My Cactus Turning Black?

If your Cactus is turning black, this is a sign that it is in immediate trouble, and you will need to act quickly to fix the problem.

A Cactus can turn black due to overwatering, root rot, crown rot, fungal infections, bacterial infections, injury, or even frost damage. 

A Cactus turning black can be challenging to save but not impossible in most cases. Once you discover why your Cactus is turning black, you will be one step closer to helping it on its way to recovery.

What Does it Mean if a Cactus is Turning Black?

If your Cactus is turning black, the foliage has started to die. This is true regardless of whether the reason is a fungal problem or an overwatering issue. If left untreated, the rest of the Cactus can eventually die. 

What to Do if a Cactus is Turning Black?

If your Cactus is turning black, the first thing you will need to do is figure out the reason why so you can do your best to correct the problem. If more than 30% of your Cactus has turned black, especially if the black portions are toward the base of the Cactus, your best solution may be to cut away the black parts and attempt to start over. 

Why is My Cactus Turning Black and Mushy?

If your Cactus is turning black and has also become mushy, then it is likely suffering from overwatering. Cacti are desert dwellers, so they are used to living in very arid and warm conditions and can withstand drought periods by storing water in their foliage.

If your Cactus is turning black and the black portions are mushy, this is likely due to living in soaking wet soil for too long, causing rot. 

Overwatering and Bacteria

Cacti will go long periods without water in the wild until a soaking rain event occurs. Many people are afraid of overwatering their Cactus by giving them too much water in one sitting, so they will provide a small drink more frequently, keeping the soil moist.

Unfortunately, this will often cause your Cactus to experience root rot, where the root system deteriorates and becomes mushy. As a result, they are unable to do their job of absorbing water from the soil and become more vulnerable to bacterial or fungal infections.  

Why is My Cactus Turning Black at the Bottom?

Root rot
If your Cactus is turning black at the bottom, it could mean rot has traveled from the roots to the bottom of the Cactus. This is also known as crown rot. Your Cactus might also turn black if the base has been exposed to water, causing crown rot. 

Crown Rot Cactus

If your Cactus soil does not drain effectively, water can sometimes pool at the top of the soil, causing crown rot. Some sellers will glue decorative rocks to the top of the soil, which doesn’t allow the water to drain through effectively, so the bottom of the Cactus will be soaking wet until the foliage rots.

Remove the rocks immediately if you purchase a Cactus with stones glued to the top of the soil. While the rocks may add a decorative element, they can prevent water from draining and will lock moisture in the soil, and prevent any evaporation. 

Can I Save A Rotting Cactus?

It can be challenging to bring back a Cactus that is rotting. In most cases, you may be better off pruning portions of the Cactus that are not rotting and starting over if possible. You can propagate several Cactus varieties by leaf, stem, or sectoral cuttings.

So before you pull out the pruning shears, research your particular Cactus variety to ensure that you are taking cuttings from the correct places. 

To prevent overwatering and rot, make sure that you pot your Cactus in a well-draining Cactus soil mix, a pot with plenty of drainage, and give it long periods of drought followed by a good thorough watering. At a minimum, ensure that your Cactus soil dries out between watering to prevent future rot. 

Fungal Infections

Fungal infections, if left untreated, can cause black spots and eventually spread to a good portion of the foliage, causing your entire Cactus to turn black.

There are many ways that fungi can infiltrate your Cactus, but some of the easiest ways this can happen are through an unsterilized open wound. This could be from pruning your Cactus with unsterilized instruments or parts of the Cactus breaking or falling over. It can also happen due to root rot or water sitting on top of your Cactus’ foliage for too long, causing rot. 

You can treat fungal Infections with a fungicide found over the counter at garden centers or big box stores, or you can experiment with homemade remedies. However, if the fungal infection has spread and your entire Cactus is turning black, your best solution would be to prune any foliage that isn’t infected and attempt to regrow a new Cactus plant through propagation. 

Research your particular Cactus variety for propagation methods to ensure that you are pruning it in the correct spot. For example, some varieties you can place directly in the soil, or you can place them in water to stimulate root growth. 

When dealing with fungal infections, make sure that you isolate your Cactus to ensure that the fungi spores do not spread to other plants in your collection. 

Frost Damage

Cacti grow naturally in warm, desert climates and are susceptible to cold temperatures, snow, and especially frost. Fortunately, we can replicate these conditions in our homes, but your Cactus may have encountered extreme cold temperatures causing it to turn black. Your Cactus may have come into contact with frost or frigid temperatures if:

  • Leaving a Cactus outdoors during an unexpected frost event. 
  • Your Cactus could be touching a cold window pane. 
  • Your Cactus lives near an open window in freezing temperatures.

Unfortunately, if your entire Cactus gets exposed to frost, it will eventually turn completely black and shrivel. However, if an arm or leaf has blackened due to temperature damage, you can trim away the black parts of the Cactus and move your Cactus to a warmer location. 

How Do You Save a Black Cactus?

cactus in pot
If your Cactus has gone completely black, it is unlikely that you can salvage it, but if it is slowly turning black, there is some hope. Here are a few things that you can do to save your Cactus: 

Trim Away Any Black Parts 

Trimming black portions of your Cactus will help prevent the problem (rot, fungus, or frost damage) from spreading to the rest of your Cactus. 

Give Your Cactus Plenty of Light and Warmth

If you want to encourage your Cactus to recover, give it ideal living conditions. This means giving it plenty of sunlight, warm temperatures, and dry conditions. 

Give Your Cactus Fresh Soil

You will want to change out your Cactus soil for fresh, ideally sterile, chunky, and airy soil. 

Use Warm, Distilled Water

Avoid shocking your Cactus while it is recovering by using distilled water at room temperature. 


Some reasons your Cactus is turning black could be overwatering, root rot, crown rot, fungal infections, bacterial infection, injury, or even frost damage. Cacti are used to living in desert like conditions, with dry, arid temperatures and occasional bursts of rain. If your Cactus is receiving too much water or its soil and pot aren’t well-draining, it could be susceptible to bacteria and root rot. 

To help your Cactus recover from damage, trim away any black parts, place it in a warm, sunny spot, provide a new cactus soil mix, and use room temperature distilled water.

In most cases, if your Cactus is turning completely black, the road to recovery will be long and uncertain, but not impossible. The faster you act to treat your Cactus, the higher the likelihood that it will make a recovery.