Why is My Cactus Dying? (How to Save it)

Why is my cactus dying

Is your cactus ailing, and are you unsure why? Cacti are commonly hailed as a foolproof houseplant for beginners, but I find they are usually the victims of too much kindness.

The reason for a rotting, dying cactus is because of overwatering, slow-draining soils, and cold temperatures, which cause the cactus to turn brown or yellow with a soft, mushy texture. Cactus are drought-resistant plants that need the potting soil to dry out between each bout of watering.

Keep reading to learn why your cactus is dying from the bottom (basal rot disease), dying from the top downwards (stem rot), dying in Winter or why your cactus is dying after repotting, and how to implement the solutions to save your dying cactus…

Cactus Dying From the Bottom-up (Basal Rot Disease)

Desert cacti turn brown and soft with a dying appearance at the bottom of the plant due to basal rot disease. The rot is caused primarily because of overwatering and slow-draining soils, however, cold temperatures are often a contributing factor.

To save our dying cacti, it is important that we understand how they grow in their native environment and then attempt to replicate these conditions in our homes…

Most houseplant cacti are native to hot and dry, arid climates with low average rainfall, growing in sandy or stony soils that are well-draining and do not retain much moisture.

Cacti develop basal rot disease at the bottom of the plant that spreads upwards with a brown mushy texture (sometimes causing the cactus to lean) if they are in conditions contrary to their dry native environment.

The most common mistake I see is because people of water too often, or their cactus has been planted in ordinary potting soil that retains too much moisture around the roots.

I must emphasize that cacti need to be in a gritty specialized potting mix that replicates the soil structure of its natural habitat and only watered when the potting soil has dried out completely to be healthy and avoid rotting at the base.

Cacti Dying at the Base in Winter

Whilst basal rot disease can occur at any time of year, this is a problem that is most often reported to me for a cactus dying in Winter.

This is because cacti are in a state of dormancy in Winter, where they do not grow due to the cold Winter temperatures and fewer hours of light.

Cacti should be watered less often in Winter, during dormancy in comparison with active growth in the Spring and Summer when there is a higher demand for water.

I made the mistake of watering the cactus at the same frequency in the Winter as in the Summer. The lack of demand for moisture in Winter means the cacti’s roots are uptaking water at a much slower rate, if at all. This meant my potting soil stayed damp for much longer, which promotes the conditions for both stem rot and basal rot disease.

The cold temperatures can also be contrary to some species of cacti preferred conditions, which promotes rot; however, cacti are a diverse family of plants, and some cacti are perfectly capable of tolerating cold temperatures as long it does not go below freezing.

Personally, all my cacti houseplants have been fine when grown indoors as they are very comfortable at room temperature.

The only exception I can think of is if your cactus is on a cold window sill and potentially in contact with the cold window pane. This is the sort of scenario that can give cacti cold stress.

Usually, the bottom of the cactus turns brown or yellow with a soft, mushy texture, which can spread upwards and cause the cactus to die back.

However, I have personally saved a cactus with basal stem rot…

Save a Cactus Dying at The Base

To save a cactus dying at the base it is important that you first address the environmental problems that caused the basal stem rot disease in the first place.

This means watering with the right frequency at different times of the year and possibly repotting your cactus into well-draining soil that mimics the soil of the cacti’s native range.

  • Only water a cactus when the soil has dried out completely. Cacti grow in an environment where they experience a deluge of rainfall followed by a period of drought. Therefore, it is important to replicate this cycle of watering indoors to prevent and treat the rotting base.

The best method I have to establish the optimal watering frequency of a cactus is to feel the soil at the bottom of the pot through the drainage hole in the base. If the soil feels damp, then delay your watering for a few days. If the soil feels dry, then this is the perfect time to water cacti.

I would also urge you to pick up the cactus’s pot after watering to assess the weight and then periodically afterward, as it should feel progressively lighter as the soil dries out. I do this regularly to gauge the correct time for watering.

  • It is important to acknowledge that cacti should be watered far less often in Winter while they are dormant. Typically, I only water my cactus every 4-6 weeks in Winter to avoid rot. Cacti can always cope much better with underwatering than overwatering, so if in doubt, delay watering for a week or so. It is worth checking to see whether the soil at the base of the pot is damp periodically.
  • If you have potted your cactus in ordinary potting soil, then it is likely that it is retaining too much moisture for the cactus to tolerate, and this is the reason your cactus is dying from the bottom. Repot the cactus in succulent and cacti soil (available online and in garden centers), which is composed of gritty soil that replicates the soil conditions in the cacti’s native environment.
A gritty succulent and cacti soil mix has a well draining soil structure to prevent cacti developing root rot.
A gritty succulent and cacti soil mix has a well-draining soil structure to prevent cacti from developing root rot.
  • Clean the cactus’s pot with disinfectant, as the pot can still harbor the fungal pathogens that cause basal stem rot. I use hot soapy water to kill all fungal pathogens.

Once you have corrected the environmental conditions, then it is possible that the cacti can recover, but I would strongly recommend that you take a cutting from your cactus for propagation as even if you create the optimal conditions for the cactus, it is possible that the basal stem rot spreads and kills the cactus.

Cacti with pads are very easy to propagate.
Cacti with pads are very easy to propagate.

Cacti are extraordinarily capable of growing from propagated sections, cuttings, and offsets from the remaining healthy growth. I have personally propagated my cactus many times. Who doesn’t love free plants? This is an easy and fun way to grow a cactus. Watch the helpful YouTube video for a great visual guide to propagating cacti…

Cactus Dying From The Top (Soft Brown and Mushy)

If a cactus is dying from the top downwards with a dried-out tip and a brown, soft, mushy, textured layer underneath, it is due to stem rot, which is caused by overwatering, slow-draining soils, and cold temperatures.

These three factors (overwatering, slow draining soils, and cold temperatures) are responsible for basal stem rot (rotting from the bottom upwards) and any rotting from the tip downwards or any other brown or yellow dying mushy section of cactus.

Therefore the treatment is more or less the same as I stated previously.

Correct any environmental problems by (as described in the section of the article above):

  1. Only water when the soil is dry,
  2. Reduce watering frequency in Winter.
  3. Plant cacti in ‘succulent and cacti soil’ to improve drainage.

I would also recommend that you plant cacti in terracotta or unglazed clay pots as they are porous which allows the soil to dry out more evenly after watering, whereas ceramic or plastic pots are impermeable and retain moisture which promotes the conditions for rot. Often, when people tell me their cacti are dying, they are in plastic pots.

Terracotta or unglazed clay pots are porous which dry out more evenly, creating the optimal conditions for cacti.
I prefer to play not cacti in Terracotta or unglazed clay pots are they are porous and dry out more evenly, creating the optimal conditions for cacti.

In terms of specifically treating a cactus that is rotting and dying from the top downwards, it is essential that you cut the brown rotting section off with a sharp pruning tool way back to healthy growth.

When this happened to my cactus, I cut it back to healthy green growth, as this reduces the chance of the rot spreading. The wound where the cactus is cut should callus over, and in my experience, the cacti can survive. However, the wound where the cacti are cut is still vulnerable to infection.

Therefore I recommend that you sterilize the wound with a natural fungicide called ‘neem oil’ which is a natural, non-toxic oil that has anti-fungal properties and should help to prevent the wound from being reinfected.

If there are any offsets growing from the cactus, then I would recommend cutting these off for propagation, just in case the problems of rotting from the top persist on the main plant.

Why is my Cactus Turning Soft, Brown, or Yellow and Mushy?

The most common reason I see for cacti is turning soft, brown, and mushy in sections is a type of stem rot also caused by overwatering, slow-draining soils, and cold temperatures. Desert cacti are drought-resistant plants and do not tolerate excess moisture around the roots which causes the brown, rotting, mushy areas of the cactus.

Therefore, it is, again, important to follow the same steps of only watering when the soil is dry, scaling back the watering in Winter, and planting the cactus in well-draining, gritty soils.

Cut out any brown, soft, rotting sections out of the cactus completely back to healthy, normal, non-mushy growth with a sharp pruning tool, or the rotting, mushy sections spread and cause the entire cactus to die back.

I would recommend sterilizing the wound with a fungicide such as neem oil to prevent any reinfection and spread of rot.

If you are repotting the cactus, it is worth looking at the roots to check whether they are healthy or rotting.

  • Cacti roots that are healthy should appear white (or light brown) with a firm texture, whereas roots that are rotting appear slimy and dark brown with an unpleasant smell.
The healthy, white roots of a cactus with a firm texture. Diseased roots are dark brown, mushy and have a foul smell.
The healthy, white roots of a cactus with a firm texture like the ones in this photo. Diseased roots are dark brown, mushy, and have a foul smell.

I would snip back any roots that are rotting back the base of the cactus. Repot the cactus in succulent and cacti soil and discard the old soil as it can harbor the disease that causes the roots to rot.

Wipe the blades with a cloth soaked in alcohol disinfectant between each cut to prevent spreading the fungal pathogens from diseased roots to healthy sections of root.

Clean the cacti’s pot with disinfectant and repot the cacti.

Whether or not the cacti are going to recover, I find, depends on how severe the root rot is, but the cacti are capable of growing new roots and surviving.

If possible, I would also consider propagating any offsetts, pads, or cuttings from the cactus in case the main plant dies back.

My Cactus Dying After Repotting…

The most common reason I come across for a cactus dying after repotting is usually because of root rot due to compacted soils, slow-draining soils, or because the new pot does not have drainage holes in the base, causing the cactus to turn brown soft, and mushy.

A common mistake I see when repotting a cactus is over-potting, which is when the cactus is planted in a pot that is significantly larger than its previous pot.

Larger pots have a greater capacity for soil and, therefore, a greater capacity to retain moisture. If there is too much moisture around the roots of the cactus for too long, then the roots start to rot, which results in a soft, brown, rotting cactus.

How to Save it…

To save your cactus, I recommend repotting it into a pot that is only an inch or two larger than the previous pot. If the pot is of a similar size, then the soil should dry out at a similar rate, thus mitigating the risk of root rot.

Repot the cactus in succulent and cacti potting soil as this imitates the soil type of the cacti’s natural environment, with excellent drainage.

Succulent and cacti soil replicates the soil conditions of the cacti's native environment,
Succulent and cacti soil replicates the soil conditions of the cacti’s native environment,

I would look at the roots to see if they are rotting (dark brown with a soft, rotting texture and foul smell), in which case cut the rotting roots back to healthy growth with a sterilized pair of pruners.

Wash the pot with disinfectant before repotting to remove any fungal pathogens and ensure that the pot has drainage holes in the base.

Always empty saucers and trays underneath the pot of excess water regularly to ensure good drainage and prevent root rot.

Cut any soft, brown, or yellow rotting sections of cacti back to healthy growth with a sharp pruning tool to prevent rot from spreading, and treat the wound with a fungicide such as neem oil.

Again, from my personal experience, if your cactus is rotting anyway, I personally recommend propagating the cactus from any remaining health growth as cacti propagate easily, and it could be the best way to save the plant.

Key Takeaways:

  • A cactus turns brown and soft and dies from the bottom because of basal rot disease, which is due to overwatering, slow-draining soils, and low temperatures. Cacti need the potting soil to dry out completely between each bout of watering, or they start to rot and die back.
  • A cactus turning brown and dying from the top indicates the soil is too damp from overwatering and poor drainage.
  • Usually, the reason for a cactus dying after repotting is because the cactus is overpotted, and the soil is not drying out fast enough, causing the roots to rot. Always re-pot cacti in pots that are only 2 inches wider than their previous pot to prevent overpotting, resulting in root rot.
  • Cacti die in Winter if the soil is too damp and the temperatures are too cold. Cacti are dormant during Winter and have a much lower demand for water. If you water the cacti as often as Summer then cacti are likely to die of root rot or basal stem rot disease.

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