Recently, some of my cacti have turned yellow. This never happened to me before and I’ve had good luck with most of my cacti. So I quickly did some investigating and found out why they turned yellow and what I could do about it.  

 

Why do cacti turn yellow? 

Firstly, there could be more than one reason why the plant is turning yellow. If the cactus is turning yellow from the top, the most common and likely reason would be sunburn. It may sound ironic because we think of cacti as sun-loving, desert plants. But not all cacti thrive in full sun and some require light or partial shade. Cacti bought from the store or nursery may also suffer from sunburn if they are not accustomed to bright, outdoor lighting. 

If this is the case, simply provide some partial shade during the hottest days of the year and the plant should recover. It would also help to learn about the cactus’ lighting requirements. Some take to full sun really well while other plants do better in light shade. 

However, if the cactus is turning yellow from the bottom instead of the top, it usually is more serious. The most common reason for this is being too wet and worse, root rot.  This is when you see yellowing from the bottom of the plant that soon spreads to the top. You will notice the plant becoming soft and mushy when touched. These are signs of root rot and when this happens, it is harder to remedy and save the plant. 

The plant may have stayed wet for too long either from too much water, or the soil not drying fast enough, or both. It is also important to check the type of soil you are using for your cactus. Sometimes over watering may not be the only culprit to constantly wet soil. The soil itself may not be drying fast enough and keeping the roots of the plant constantly wet. Make sure you are using a fast draining soil. 

Commercial cactus potting mix combined with perlite or other porous material to add drainage would be good enough. A solution of 2:1 potting mix and perlite would be good to start with. Others like to add coarse sand to improve drainage. Here’s where you can find some of my soil and soil amendment recommendations online.

One of the most damaging things you can do to a cactus is exposing it to extremely cold temperatures in the winter and also keeping it wet, which is what happened with my plants. We had a very cold and wet winter season that just passed and some of my cacti did not fare very well. 

Since I live in Northern California, I keep all of my cacti outdoors all year and let them weather the rain and cold during the winter. Most of the time they are fine but this year the rain was above average and my plants just became waterlogged. 

Cacti usually like to stay dry during the colder months when they go through a dormant period. And some cacti are not very cold hardy to begin with. Exposing them to wet and cold can be disastrous for the plant. 

Another less common reason for yellowing is pest infestation. Inspect the cactus closely and see if you notice any creepy crawlies around the plant. If you notice little red bugs that look like tiny red spiders, those are spider mites. Spider mite infestation can be deadly to the plant if it is severe. Treat right away by spraying with rubbing alcohol. Separate the pest infested plant or it can quickly spread. Make sure to keep the plant away from direct sunlight after spaying with alcohol to prevent sun damage. 

Other common pests could be aphids and mealybugs. Check to see if you find any white fuzz around your plant because these are telltale signs that you have mealybug infestations. These pests suck on the tender parts of the plant, causing damage. To get rid of them, wipe the plant with rubbing alcohol. You can also spray the plant with soapy water to kill the bugs. You may also need to repot the plant and remove from the soil to make sure there are no eggs hiding and waiting to hatch. For more on this topic, visit my post on “Common Pests On Succulents and Easy Treatments for Them”.

Yellowing can also happen to newly bought plants that are repotted into a new pot with fresh soil. The plant can turn yellow from shock and changes in watering techniques. When repotting, make sure the pot you are transferring the plant to is not much bigger than the current nursery pot it’s in. too much soil can shock the plant, especially a small plant.

Why is my cactus turning brown?

Instead of yellow, a cactus can also turn brown. The most common reason for this is age and is called corking. Corking happens naturally when a cactus matures. It occurs from the base of the plant where it touches the soil and can move up slowly or can stay in one spot. Corking gives the plant a woody appearance. The plant is otherwise healthy and firm to touch. 

When the plant turns brown and is mushy or soft to touch, then you have a different issue going on. This is usually a sign of rotting or disease, or both. When a cactus has been constantly wet, rot can settle in from the roots and spread upward to the plant. Diseases such as fungal disease or from pest infestation can also turn a cactus brown. Often the browning happens from different parts of the plant and it will not be firm to touch but feels soft and mushy. 

cactus yellowing from the bottom

Why is my cactus drooping and shriveling?

When a cactus shrivels and droops, the most common reason is underwatering. The plant will appear wrinkled and will be soft to touch. A healthy cactus should be firm to touch and not droopy and soft. 

While the most common reason is underwatering the plant can also droop and shrivel when it is overwatered. This is usually accompanied by yellowing from the bottom of the plant, which helps us to identify the reason for the drooping. 

Why does the cactus feel soft?

When the cactus feels soft, it’s not always due to overwatering and rot. Sometimes it can be a sign that the plant is severely dehydrated. Cacti and succulents have water storage capacities and can withstand droughts for long periods of time. However, this does not mean they do not need water at all. 

Cactus plants like a good drink of water, especially on hot summer days. Left without water for too long and they begin to deplete their water storage. This is when you see them becoming soft. The plant can also turn yellow from lack of water and being too dry. Usually the plant will also appear shriveled or wrinkled. When this happens to your plant, give it a thorough watering and it should perk up within a day or so. 

When there is yellowing from the bottom and the plant feels soft and mushy, the damage to the plant is more severe. The plant is rotting from the roots. The most common cause for this is overwatering, or the plant has been exposed to extreme cold, or extreme heat, or all of the above. 

Can you save an overwatered cactus?

Yes, but it depends on the extent of the damage to the plant. The less severe the damage is, the better chance the cactus has of recovering. The first thing you need to do with an overwatered cactus is to stop watering the plant. If you have set a schedule to let’s say water the plant once a week, stop doing so and allow the plant to dry out and recover. 

Steps on how to save an overwatered cactus:

  • Remove the cactus from the wet soil and clean the roots.
  • Let the plant dry out completely for at least three days to a week. 
  • Place the plant somewhere bright and dry, but away from direct sunlight to avoid burning the plant and drying out the roots completely.
  • Once dry, replant in a suitable well draining potting mix and do not water immediately. Wait about 2-3 days before watering. Water thoroughly and do not water again until the soil is dry. Refrain from overwatering again.
cactus turning yellow from the bottom up

Can you still save a dying, rotting cactus?

Again it depends on the extent of the damage to the plant. Obviously, the more damage and rot the plant has, the harder it is to save. It is a good idea to try to save the plant as soon as your notice rot setting in. Once rot is severe, there is very little else you can do. It also depends on how mature and established the plant is. Bigger, more established plants will have a better chance at surviving than smaller, baby cacti. 

Once rot sets in, you need to act fast if you want to save your plant. 

Steps on how to save a rotting cactus:

  • Inspect the cactus for severity of the rot. Find parts of the plant that you can salvage such as firm, green parts. 
  • Cut off parts that are mushy and rotting, including the roots. Save any green, firm or viable parts of the plant. You will know if it’s viable or not when you cut the plant. If the inside shows green parts, not brown or black, these may stand a chance and can be propagated to start a new plant.
  • Place the saved parts somewhere dry and out of direct sunlight. Allow to dry for a few days to a few weeks until all the cuts have calloused and sealed. (Optional: dust some sulfur powder on the wounds of the cactus. Sulfur powder can help prevent infection and is commonly used as a fungicide. Here’s where you can find sulfur powder.) 
  • Prepare a well draining potting mix. I usually use cactus mix combined with perlite. You can also add coarse sand to the mixture to add more drainage. Here are some of my soil and soil amendments recommendations.
  • Once the wounds have healed and dried, stick them in soil.
  • Water the soil when it feels dry.  Keep away from direct sunlight until fully rooted to avoid burning the plant.

How to prevent this from happening again?

Learn the basics of cactus care. Provide a well draining soil (see above for recommendations). Water only when the soil feels dry. The top inch of the soil should feel dry before you water again. Give plenty of light but take care not to burn the plant. 

Sometimes the plant may be too far gone and there is nothing you can do to save the plant. Once the entire plant tissue becomes mushy, there isn’t much you can do to save the plant. Don’t beat yourself up over it. You can always try again and see if you have better luck next time. Sometimes it’s not even your fault. The plant may have been on its way out before you had your hands on it.  

cactus turning yellow from the bottom

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cactus yellowing from the bottom
cactus turning yellow from the bottom