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It’s fun to grow succulents like cactus in your garden and they need low maintenance. But if you find your cactus turning black, you need to figure out the problem fast.

Your cactus may be turning black because it’s infected by a bacterial or fungal disease. This can also happen if you’re overwatering or underwatering the plant. Another reason for the black spots could be a change in temperature has occurred.

I’ve written my research below on finding out exactly what is causing your cactus to turn black and how you can treat the problem.

You’re Overwatering Your Cactus

Overwatering is one of the most common reasons plants begin to rot and eventually die. Your cactus needs a certain degree of drought in order to survive.

The roots of your plant will rot if they are subjected to too much water, and they will eventually die if you’re not careful. Once the roots have become fully affected due to rot, you’ll start to see black spots build up on the surface.


It’s important to remember that your cactus is a very low maintenance plant, and therefore requires less care and even less water. Your best bet to avoiding black rot on your plant is to cease overwatering immediately.

Unfortunately, if your cactus has begun suffering from black rot and you can see black spots forming, it’s unlikely you can save your cacti at this point. It’s best to avoid overwatering in the future and be mindful of how and when you water your drought-tolerant plant.

Give your cacti time to dry out before you begin watering it again. This may contradict everything you know about caring for plants, but your low maintenance cactus will appreciate it in the long run.

You’re Underwatering Your Cactus

As we stated above, your cactus is a very low maintenance plant, but it’s important to note that your cactus still needs water to survive.

This is another common theme amongst problems that cactus owners face, which is their plant turning black due to underwatering.


As we discussed earlier, it’s important to allow your plant a time to dry out before watering. You don’t want your plant to become so dry that the roots begin falling and breaking apart.

Underwatering can have the same effect that over-watering can, and black spots can begin forming on different areas of your plant.

It’s important to be mindful of the watering practices you take part in while caring for your plant. The last thing you want to do is not give you cactus enough of what it needs to continue thriving and growing stronger.

Your Cactus Is Suffering From a Bacterial Infection

Under certain conditions like a moist environment, your cactus can be subjected to certain bacterial and fungal infections that are fatal. But with some bacterial infections, your cacti can be saved if you catch the problem early enough.

For example, dry rot is caused by several different fungi that develop on the pear pads of your cactus. Dry rot is likely to have formed when the prickly pads of your cactus have come into contact with splashing water.

The fungus from the soil or underground can make its way to the surface of your plant through splashing water. For instance, when it’s raining or when you’re watering your plants. You can easily avoid infections like dry rot from occurring when you keep the pads of your cactus dry.


Your best bet to avoiding dry rot is to check in on your cactus often. Ensure that your cactus’ pear pads do not stay moist or come into contact with water often.

If you’ve begun to see black spots forming on your cacti, you can easily resolve the issue by cutting off any infected areas of your plant.

Other key steps you can take, involve isolating your cactus from any other surrounding plants and removing and replacing the soil that your cactus is surrounded by.

As for isolating your plant, this is for the other plants’ safety, so your entire garden isn’t subjected to the same bacterial infection.

You’ll also want to remove and replace the soil for the same reason, as the soil has obviously been corrupted by bacteria and is hurting your plant. It’s best to dispose of it and replace it with fresh new soil that will allow your cactus to regain its health.

It’s important to remember that it’s easier to save a cactus that has begun to rot from top to bottom, as opposed to bottom to top. When the roots have been infected first by any kind of rot or infection, it’s much harder to save the plant.

Changes In Temperature Have Occurred

Your cactus is also capable of turning black when subjected to colder climates. Thankfully, black spots on your cacti due to the cold are easier to fix and ultimately heal in the long run, so they’re not too serious.

It’s important to know that your cactus does not do well in cold and harsh climates, so if you can, it’s best to avoid keeping your cactus in these kinds of environments at all costs.


If you feel as if your cactus has begun turning black due to the cold, the first thing you should do is remove it from that environment. Once you’ve changed your plant’s surroundings, it’s ideal to just be patient and allow your plant to restore its tissue, which will, in turn, remove the black spots from your cacti.

If your cactus grows indoors, remember to keep the windows shut during the colder months. It’s also ideal to leave the thermostat in your home at around 75-80°F (23.9-26.7°C) during the winter months in order to ensure your plant is comfortable.

When the colder seasons creep around, it’s important to be mindful of where your cactus is and what kind of conditions they’ll be subjected to on a regular basis.


So hopefully now you have a better understanding of why your cactus may be turning black.

While your cacti may come in many different sizes, shapes, and colors, certain colors such as black spots will let you know that something has gone wrong. We explored some of the issues your plant may be experiencing if black spots begin to show.

For starters, we explored how overwatering, as well as underwatering, can affect your plant’s roots, as well as their prickly pads. It’s also possible that your cactus is suffering from a bacterial infection, and it should be dealt with immediately.

Your cactus can also turn black as a result of harsh and cold climates. Now that you have a better understanding of what may be causing your cacti to turn black, you have all the necessary tools you need to keep your plants healthy and happy.


Here are some of my favorite container gardening tools

Thank you for reading this post. I hope it helps you with your gardening needs. I’ve listed some tools below that can help you with container gardening. These are affiliate links so I’ll earn a commission if you use them.

Gardening Gloves – I find the Pine Tree Tools Bamboo Gardening Gloves really good for both men and women. It’s made from bamboo so helps absorb perspiration. They are also comfortable and fit very well.

Containers – You know picking the right container is crucial for your container gardening. I’ve written a detailed post on the best containers you can choose from. If you’re happy with a plastic container, you can check out the Bloem Saturn Planter.

Watering Can – This is a must-have tool when you’re growing plants in pots or grow bags. It helps to water the potting soil without splashing on the foliage. The Kensington Watering Can is stylish, strong, and can provide precision when watering potted plants.

TrowelGarden Guru Trowel is my favorite because it’s durable and comfortable to use. My gardening friends really love having a trowel because they use it for digging soil, mixing fertilizer, moving seeds, leveling out the soil, mixing compost or mulch, and also dividing tubers

Bypass Pruner – I really like the Corona Bypass Pruner because it’s durable and gives a clean cut that helps plants recover faster. If you’re looking for something cheap, get the Fiskars Bypass Pruner that is really good as well.

To see an extensive list of the best container gardening tools gardeners recommend, check out this resource that I made for you.