Why Is My Cactus Turning Black: Spotting Fungal Diseases To Save Your Plants

An image of a cactus spread out on a sheet of paper.


Like most other life forms, a sudden change in the color of a cactus is not a good sign. When your cactus is turning black, you should always ask why. The answer is sadder than you might expect. There are no naturally black cacti. Unless yours somehow ended up on fire, that black patch is a nasty bacterial infection. In short, your cactus is rotting and dying. Can you save it? Sometimes you can, or you may be able to take a healthy cutting and grow a new plant from it. Either way, your cactus has a long road to recovery. I will explain what causes this in detail and share ways to try and save the rotting cactus. Additionally, I will also share some other common cactus issues and what you can do about them to keep your spiky plants happy and healthy.

Why is my cactus turning black? Your cactus is turning black because it has a bacterial infection. Worse still, the rot that eats cacti, turning them black, can spread to other plants. You’ll need to move quickly and cut away the infected sections to prevent the spread of infection. Isolating the infected plant can also help. 


Why Is My Cactus Turning Black

The reason why tour cactus is turning black is a lot more serious than you might expect. Fire will burn a cactus black, but there’s only one non-burn-related problem that causes blackening. Your cactus probably has a contagious fungal disease.

You will need to move this cactus away from other plants for a while to prevent the spread. Moreover, there’s cactus surgery in your future. Unfortunately, you will have to cut away the infected sections.

I recommend cut and stab-proof gloves and a long sharp razor knife. The gloves will help save your hands, and the knife will help save the cactus. Razor knives are exactly as sharp as they sound so that they will do the least amount of damage to your plant. Having a clean-cut wound to heal is less work, and recovery is faster and more likely.

There are many different fungal diseases, but they all have the same solution. For example, your cactus may have phyllosticta pad spotting, bacterial necrosis, or crown rot. Ultimately, you still have to cut it off and treat it with a fungicide to save the plant.

When you’re done, ensure that you feed the cactus well and water it unless overwatering contributed to the issue. Doing this will give your cactus a better chance of healing.

Keep your sick cactus healthy by feeding it EarthPods Premium Cactus & Succulent Plant Food from Amazon. This outstanding blend offers desert plants the perfect mix of nutrients to help them flourish or heal. You’ll appreciate the no-smell, no-mess, no-measuring necessary proprietary formula. Best of all, these eco-friendly, sustainable EarthPods are made right here in the USA. Read the stellar reviews for yourself by clicking right here.

How You Treat Black Fungus On A Cactus

You cannot always save an infected cactus. That said, if you give it the right TLC and catch the condition early, you can cure fungal diseases. Start by doing everything you can to avoid fungal infections in new plants.

To begin with, always plant in sterile soil, ensure good ventilation, and use purified water. You can also treat plants regularly with a fungicide to prevent growth. Sadly, your plant may already have an infection, so I’ll go over curing it as well.

Begin by sprinkling your plant with copper fungicide, per the instructions on the package. Doing this will kill fungal spores. If you caught the infection early, this might be enough to stop it in its tracks and prevent worsening.

Next, cut away the infected sections. Keep your cactus in a sterile environment until it heals over the cuts, and watch out for possible reinfection.

Once you’ve handled that nasty black fungus, give your cacti some Schultz Cactus Plus Liquid Plant Food. Regular feeding with this fantastic 2-7-7 blend will help ensure your plants grow back stronger than before. All you have to do is follow the directions on the package to dilute the fertilizer and feed your desert plants. You’ll see the difference in as little as a week. Get Schultz for your cacti by clicking here


What Does An Overwatered Cactus Look Like

It is a myth that cactus do not like or need water; in fact, they love it so much they will save every drop even when it makes them sick. Too much water won’t necessarily make your cactus turn black, but it can cause a slew of other issues. How do you spot an overwatered cactus?

Luckily, it is easy to identify cacti watering issues. Because they save all the water for the many rainless days in the desert, a plump, round cactus is water-rich. Look out for the following problems to identify an overwatered cactus.

  1. Rotting- Signs of rot in cacti are frequently the result of too much water. These highly specialized plants can only take so much before it quite literally starts to kill them.
  2. Root Rot- Like body rotting, cacti that are overwatered are especially sensitive to root rot from overwatering. Make sure you leave them in well-aerated soil.
  3. Drooping and Sagging- Water is heavy, and it makes the absorbent inside of the cactus softer. These normally firm and upright plants will sometimes slump over when they have too much liquid inside.
  4. Mushy- When you touch a cactus between the spines, it should be firm like leather. If it squishes under your finger, then your cactus is waterlogged. The spines may become soft and floppy, but this is less noticeable, and I do not recommend touching cactus spines.
  5. Chlorosis- Yellowing of plants caused by lack of chlorophyll is another obvious sign of overwatering. Water stored inside the cactus blocks direct sunlight.
  6. Edema- Blisters may form on the cactus’s surface as it tries to find new storage places for the water it cannot stop drinking.
  7. Low Growth- Whether the pant is stunted over time, or it simply doesn’t flower as much as it should, overwatering leads to long-term noticeable side effects as well.

If your cactus is showing signs of overwatering, stop giving it water. These unique plants are evolved to go without a drink for long periods, and it will be fine as it dries back out.


Why Is My Cactus Turning Dark Green

Some species of cactus are naturally rich dark green. Pay close attention to make certain your cactus is not turning black instead, but most often, that green is nothing to worry about. Deep, colorful plants are usually just happy and well-fed.

In rare cases, an overwatered cactus that was originally a very pale green may look darker as it becomes waterlogged. However, this effect is uncommon. Most cacti turn pale instead of darkening when there is a problem.

Intriguingly, an underwater cactus may also look a little darker. As it shrinks in on itself, it may even begin to brown a little. Regardless, a shrunken, darkened cactus probably needs a little drink.


How Do You Save A Dying Cactus

When your cactus is turning black or otherwise dying, it can be extremely upsetting. Fortunately, there are plenty of ways to help a cactus survive. More importantly, these incredibly hardy plants are already survivors, and they will fight for life in the harshest conditions.

Firstly, take a look at how much light your cactus is getting. These are desert plants that want full sun daily. If yours is in a dark corner, it will not be happy. Move it as needed to get the right amount of light each day.

Check the temperature as well. Cacti are hardy, but even s, they can freeze or overheat. Especially if you have them near a vent where the temperature changes rapidly, this can contribute to health problems.

Water your cactus enough, but not too much. Cacti need well-aerated soil and pots that drain so their roots can dry out between waterings. Moreover, they like low nitrogen fertilizer. Also, make sure you are planting in cactus and succulent blend soil for happy cacti.

Make sure you cut off any rot or fungus and keep your cactus away from pests. Finally, it would help if you dusted a cactus now and then. Accumulated debris will block the light your plant needs to survive.

When your cactus needs extraordinary care, stick to a well-known and trusted name in plant feeding. Grab a bottle of Miracle-Gro Foaming Succulent Food from Amazon and nurture that sick cactus right. You can apply this simple spray-on every two weeks directly to the soil, so your healing cactus has all the nutrients it needs to heal. Have Miracle-Gro delivered to your door fast when you click here.


Final Thoughts

A black cactus isn’t some cool gothic name for a fancy drink; it’s a real problem for gardeners. In addition to the one plant rotting, these bacterial infections can spread to other plants in the area. If your cactus is in a pot, move it away from other plants asap.

Cutting rotten sections out of the cactus is a serious business. Ensure that you wear cut and piercing proof gloves whenever possible, or use longer tools and watch your fingers. Most bacterial plant infections cannot spread to humans, but there’s no sense in risking the spines anyway.

Through trimming and serious TLC, you can often save a sick cactus. However, you should also be prepared for the worst-case scenario if the rot is extensive, your plant may die.

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