Most cactuses are hardy plants and can tolerate some errors in care. However, cacti also need some specialized care. One of the problems that you might experience with cactuses is shrinking, that can be caused due to few reasons. So why is my cactus shirking? Let’s find out in this post.
Few of the main reasons why your cactus is shrinking are under watering, aging, rotting, too much light, overwatering during winter. You will need to look for multiple signs to determine the cause of shirking.
Shrinking of a cactus is not normal, and should not happen in a healthy cactus. Please note that aging cactus will normally demonstrate some corking (brownish in color).
However, shrinking, especially at the base, indicates mistakes in care (often long-term), which can be various. Please review your cactus care to find what could be causing shrinking.
Reason #1: Too much light
Most cactuses naturally love sunlight and being exposed to bright light (sometimes shaded light). In their natural habitat, most cacti get exposed to a lot of sunlight throughout the year.
However, if you live somewhere with cold winters, you won’t get much sunlight during that period. Or even, during the year. All plants have the ability to adapt to their new environment.
So, if your cactus was not getting much light during winter and then you suddenly expose it to lots of bright light, it can easily burn. If you experience colder winter (anything below 60-65 F/15.5-18 C), you need to allow your cactus to go dormant in winter.
Once winter is over, you need to slowly re-introduce your cactus to bright light. To do this, place your cacti in bright light, but shade them with gauze or other semi-transparent cloth. Over few weeks, leading to summer, remove parts of the cloth to allow more exposure.
Never allow sudden changes from light or even temperature (keep away from drafts/air conditioning) – it is very bad for cacti. Shrinking, burns (later turning into brown corked spots) and loss of spikes can happen due to sudden light/temperature shifts.
You can read more about cactus winter dormancy in this post (new tab).
Reason #2: Overwatering/rotting
Overwatering is another cause that can make your cactus shrink. That’s because overwatering can lead to root rot, which will then spread and cause shrinking/softening of the plant.
Signs of a rotting cactus are soft stem and loss of shape. You might also see yellowish coloration around the stem, especially at the base.
Read more about rotting and other ailments in cacti in this post (new tab).
Reason #3: Not enough light
Without enough sunlight, your cactus cannot thrive or survive. If your cactus has not been getting enough sunlight over a long period of time, it will start leaning, showing thinning and elongated growth.
Without light, it won’t be able to photosynthesize, and its metabolic processes will start shutting off over time. Most cacti require bright, mostly indirect light (if you don’t get much sun where you live, full sun might be necessary).
Even in winter dormancy, make sure your cactus is placed in a spot to get maximum of available sunlight. However, it should be kept in cool conditions (around 54-59 F/12-15 C), or it will start growing and thinning.
If you keep your cactus in warm and dark conditions, it will slowly start dying. After winter is over, allow your cactus to slowly get used to stronger sun again (shade them in the beginning).
If you notice shrinking and bad smell (plus possibly yellowing), your cactus might be dead even if its roots are looking normal. That can be due to lack of light, overwatering, keeping in dark & warm conditions in winter.
Reason #4: Under watering
Under watering can also lead to shrinking of a cactus. While cacti love fast draining soil and to dry out between waterings, under watering can cause issues long-term.
Make sure to check if soil is dry and water your cactus accordingly. You can even use a soil meter for checking moisture levels in soil, like this one.
During winter dormancy you will only water once in 4-6 weeks, and only lightly. Some cacti keepers stop all watering, but it’s better to water very slightly as transpiration is still happening.
During this time, your cactus might shrink, but it should go back to normal once you continue normal watering schedules.
Read all about watering your cacti in this post (new tab).
Summary on cactus shrinking:
Your cactus might be shrinking due to different reasons. This is especially true if it’s been going on for some time. Your cactus might be dying even if most roots look normal – even partial loss or roots can lead to your cactus shrinking and dying.
The main things to review if your cactus is shrinking are other signs. Take your cactus out of the pot when soil is dry and examine roots. Do you see anything unusual there (dots, swollen roots etc.)? Pests and parasites can suck out juices out of your cactus. Is there a smell or any spots/dots? It could be rotting.
If your cactus seems to be rotting, you will need to try and save the plant. You would need to cut the healthy part and repot it in a new container. For a guide on repotting, please see this post.