Why Cacti Need So Much Less Water Than Other Plants

Cacti are known to be very resilient. They can survive in harsh environments like deserts or my cousin’s room without receiving any water for multiple years. But how are they able to live that long without the need of any or just very little water? In this article, I will explain exactly that and more.

Cacti are able to live with very little water because when they receive water then they store as much of it as possible in their stems for later use and they are utilizing a special kind of photosynthesis called CAM that allows them to open their stomata (plant pores) during the night which will result in very little water loss through evaporation.

Cacti have evolved to survive even in the harsh and hot deserts of this planet and in order to achieve this, they had to learn some tricks.

The most impressive feat is probably the CAM Photosynthesis which stands for Crassulacean Acid Metabolism. You can read more about that in my article about cacti and how they do photosynthesis differently than other plants.

But their ability to store a lot of water in their stems is also a very impressive feat that helps cacti to survive long periods of drought.

Cacti Do Photosynthesis Differently Than Regular Plants

I have another article that goes more into detail about how exactly and why cacti do photosynthesis differently than other plants so if you want to know more than consider reading that article. In this section, I only briefly go over the advantages of CAM photosynthesis and why it saves so much water.

Regular plants do photosynthesis during the day where they open their stomata (pores of the plant) in order to absorb CO2. Then they use water, the sunlight, and the absorbed CO2 to produce basically foot for the plant and, as a side product, oxygen. The oxygen is then being released by the plant, because it doesn´t need it, though the Stomata.

But during this process, the plant pores are open the whole day which will result in a lot of water evaporating from the plant. So during the Photosynthesis process, a lot of water is lost not through the process itself but also through evaporation.

If cacti were to do photosynthesis the same way as regular plants then they would dry out in a matter of days. So they had to adapt.

Cacti are only opening their Stomata at night when the sun is gone. During this time they release all the oxygen stored in the plant during the night and then they absorb as much CO2 as they possibly can.

Then they will close their stomata before the sun rises and during the day they are doing as much Photosynthesis as possible with all the saved resources that they have. Cacti are able to do this through a very complicated chemical process called Crassulacean Acid Metabolism or CAM for short.

And then at night, they will release the oxygen that they produced during the night and they will absorb as much CO2 for the next day as possible.

This way the stomata are only open during the night and this will reduce the amount of water that is evaporating to a minimum. So the cactus can save as much precious water as possible.

How Long Can A Cactus Survive Without Water

This is kind of hard to answer because it really depends on the variant of the cactus, how old it is, and how big it is.

Generally, a regular, medium-sized cactus can survive anywhere from one to two years without receiving any water. Cacti store water in their stems and they are able to preserve this water through a special kind of photosynthesis called CAM. Indoor cacti are not in their natural environment which means they are not able to survive nearly as long without water.

So cacti that are living in the desert will generally survive multiple years without any water mainly because they are able to preserve a lot of water in their stems and because they don´t use much water to do photosynthesis.

But if you are looking at cacti that are living indoors then the whole thing is looking much different.

Cacti indoors won´t be able to keep as much water in their stems as cacti in the desert would be able to store.

This is mostly because we don´t cool down our apartments or houses at night. Instead, we mostly have the same temperature at night and day during the whole year.

So when the cactus opens its pores at night it will lose more water indoors as it would in its natural environment.

Because Deserts are colder at night than our homes.

This is why cacti that live indoors will lose more water than outdoor cacti.

That usually doesn´t matter as much for the cactus as long as it gets enough water to compensate for that.

So water your indoor cacti regularly to ensure that they are healthy and don´t test how long they will survive without any water at all. Because once a cactus starts to dry out it will be quite difficult to revitalize it.


I enjoy all things outdoors and I love plants! I've never considered myself to be one with a green thumb, but it's my mission to learn, so I figured I would bring you along for the ride. :) Happy planting!

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