Why Is My Cactus Shrinking? 5 Reasons You Have A Shrinking Cactus

Some of the resources below may be affiliate links, meaning I get paid a commission (at no extra cost to you) if you use that link to make a purchase.

If you have landed on this page then chances are you’re sitting at home wondering ‘why is my cactus shrinking?’. In this article, I will be guiding you through the top five most common reasons you have a shrinking cactus.

Cacti are a popular houseplant across the globe due to their low maintenance and durability. They are part of the succulent family and native to hot, desert countries. For this reason, cactus can store water in their stems and can go long periods of time without water. 

So, why is my cactus shrinking? A shrinking cactus can be down to five main reasons: too much light, not enough light, overwatering, underwatering and rotting. Once you have figured out the cause of your cactus shrinking, then you can work on the fix! 

Need more advice on cactus care? Try reading one of the following articles: Why is my cactus turning black? Why is my cactus turning white? Why is my cactus floppy? Why is my cactus squishy? 

Help! Why is my cactus shrinking? 

cactus shrinking

A shrinking cactus doesn’t have to be a cause for concern. Once you get to the root of the problem you can work on fixing it and you will soon be back to having a healthy, happy houseplant. 

Let’s get onto the first reason you could be thinking ‘why is my cactus shrinking?’.

Cactus shrinking due to too much light

A shrinking cactus could be due to too much light. Although cactus love a bright, sunny spot, there is such a thing as too much light. 

In their natural habitat, a cactus is exposed to a lot of natural sunlight. However, these popular houseplants are adaptable to a range of weather. If you live in an area where you get a cold winter and daylight only lasts a few hours, then your plant will adapt to this. 

Going from a cold winter with little light, to a very warm summer with bright sunlight can actually cause your cactus to shrink. A sudden temperature change will also cause sunburn on your cactus plant.

Once winter is over, you should slowly reintroduce your cactus to the brighter weather. Place it in a south-facing window in a brightly lit spot but cover with a semi-transparent cloth for the first few weeks. 

Alternatively, you can place the cactus in a bright spot for a few hours in the morning, whilst the air is cooler, and then move it into the shade in the afternoon. 

Cactus shrinking due to not enough light

Vice versa, you could be thinking ‘why is my cactus shrinking?’ due to a lack of light. If your cactus has been deprived of sunlight for a long period of time, signs you will notice will be shrinking, thinning, discoloration, and elongating. 

This is called etiolation and is common in many different succulent and cacti plants. 

Light is vital in allowing your cactus to photosynthesize. Without this process, your cactus will have stunted growth and you might even notice your cactus shrinking. This will be because your plant is not getting enough nutrients and energy it needs to function properly. 

A lack of light will also cause your cactus to turn pale or discolored due to a lack of Chlorophyll, the chemical found in plants that make them a vibrant green!

You should always be placing your cactus in a south-facing window so that it gets as much natural sunlight as possible. If you are unable to do this, then I would advise purchasing a grow light with a fluorescent LED bulb that mimics daylight. 

I have this grow light from Amazon that I use on my cactus and it works a treat. It has multiple settings along with a timer function. It provides the perfect light needed for a cactus plant to thrive. This is ideal if you have only a small number of plants or mini cacti in your home. If you have a large quantity that you require lighting for, then I would invest in something a bit bigger! 

cactus getting smaller

Cactus shrinking due to overwatering

One of the most common problems you will encounter as a plant lover will be overwatering and can leave you wondering ‘why is my cactus shrinking?’. 

Typical signs of an overwatered cactus will be extremely wet and soggy soil, the stems turning soft and mushy and discoloration such as turning black.

Because of their native habitat, cactus plants are susceptible to overwatering. As a rule of thumb, you should only water your cactus once the soil is bone dry. Then you should give it a thorough soaking until water pours out of the drainage holes. Throw away any excess water and do not leave your cacti sitting in a saucer of water because this will cause problems such as root rot. 

To avoid a shrinking cactus and overwatering you need to ensure that you are using the correct soil. Cacti and succulents enjoy a well-draining soil that is made with a blend of organic and inorganic material.

The main ingredient you should look out for is perlite or peat moss. My go-to soil for cactus The Next Gardener Organic Succulent and Cactus Soil Mix. It is made with a blend of 75% substrate, 25% perlite, and low fertilizer which creates a well-draining and light soil.

However, if you prefer to avoid online purchasing, you can pop to your local garden center where you will find a ready-made cactus and succulent potting mix.

If you use soil that is too dense and heavy, then it will retain too much water and will cause overwatering.

Cactus shrinking due to underwatering

Again, vice versa, underwatering can also leave you wondering ‘why is my cactus shrinking?’. 

As mentioned above cactus store water in their stems and leaves, which gives them that plump, thick appearance. If you haven’t watered in a very long time, then there will be no water to store. Naturally, this will cause a shrinking cactus and it will appear much smaller than once before. 

Check the soil by pushing your fingers in a few inches. If it feels bone dry throughout and you are aware that it has been a long time since you watered then it is probably time to give your thirsty plant a drink! 

Once you give your cactus a thorough soaking, it will absorb some of the water and you should see the plant return to its normal size.

Even in the winter, when the cactus is dormant, it will still occasionally need watering although definitely not as often.

Do not stick to a strict watering schedule because this can lead to problems such as underwatering and overwatering. So many things affect how often a cactus needs to be watered such as the environment and seasons. Because of this, you should always stick to watering once the soil is bone dry.

my cactus is shrinking

Cactus shrinking due to rotting

The final reason you might be screaming ‘my cactus is shrinking!’ will be down to root rot.

Root rot is a horrible disease and is unfortunately very hard to recover from. There are many things that can cause a rotting cactus but overwater is the main cause. 

If the soil is wet and soggy then you should investigate further to see if you do in fact have root rot.

Lift the cactus out of its container and check the roots. Healthy roots will be white and firm, whereas infected roots will be brown and slimy. 

If you have a rotting cactus on your hands then there are a few options to try and save it. 

The first is to cut away at the infected roots and repot in fresh soil. Make sure you cut right up to the healthy roots because any infected roots left will spread once you have repotted. You may also need to prune your cactus and get rid of some stems. This is because your plant will have fewer roots, meaning it won’t be able to support as much plant matter as before. You should be pruning a similar percentage to the roots cut. 

If the root rot has unfortunately taken hold of your plant and there aren’t any healthy roots left, then the only option will be to propagate. 

Luckily, propagating a cactus is fairly easy and can be done through cuttings. 

The process is straightforward, simply take a generous-sized cutting, leave it in a dry place for a few weeks or until a callus appears, and then repot into a container with fresh, well-draining soil. 

Gardeners World has a great article on cactus propagation if you need a bit of help along the way. 

Why is my cactus shrinking? The last word…

I hope you have enjoyed reading this article on a shrinking cactus and you are no longer sitting at home wondering ‘why is my cactus shrinking?’. 

There are five main reasons a cactus will shrink and these are: 

  • Too much sunlight
  • Not enough sunlight
  • Overwatering
  • Underwatering
  • Root rot

I hope that you are able to save your cactus plant and get it back to its normal healthy self! However, if you are unable to do this, then propagation is always an option. 

If you have any questions, then leave a comment and I’ll get back to you as soon as I can. 

Alternatively, you can read some more of my posts on cactus care such as: How to make cactus grow faster and How often do cactus bloom? 

Leave a Comment