How Do Cactus Store Water

The cactus plant is notorious for its ability to go weeks without water. The drought-hardy plant is often featured in works of fiction to depict sun-beaten, barren landscapes. Experts speculate that some species can survive for up to two years without water. So why is the cactus so resilient?

The answer boils down to the thick stems of cactus plants that allow them to store a lot of water. These thick, enormous stems serve as a protective layer that prevents water loss. It is worth noting that indoor cacti are not as resilient when you compare them to the typical desert variety.

Indoor varieties will struggle if they miss two or more watering sessions (usually once every 14 days). The exact watering frequency of cactus plants depends on their species.

The table below gives a rough summary of how cacti collect and store water.

How Cacti Collect and Store WaterFunction
StomataAbsorbs moisture from the air
SpinesCollects water condensation
RootsCollect water from the ground and under the surface
Parenchyma cellsStore the collected water by expanding

How Cacti Deal with Water

Cactus plants have extensive root systems, conical spines, and unique stems that help them collect water. They have a fascinating ability to absorb and conserve as much water as possible. Studies show that many desert areas receive next to no rain. But when it does rain, it tends to be a heavy downpour.

Cacti in these conditions can gather and save water when it finally rains. Cacti in California contain water-storage cells called parenchyma within their enlarged roots. The parenchyma has flexible walls that can expand and contract to accommodate the varying water levels in the cactus.

Specialized Root Systems

Cactus species have developed specialized roots that can spread several feet away from the base of the plant. Although these roots go just a few feet deep underground, they are spread over a large area. This gives the roots easy access to water as soon as it reaches the ground.

So why are the roots shallow if it helps to extend further into the ground? This is because rain rarely penetrates the soil in arid environments. This is why it’s better to stay close to the surface to take up rainwater as soon as it reaches the surface. For the cacti species, shallow roots are an advantageous characteristic that helps with their absorption rate.

Another water-absorbing mechanism that allows cacti to survive is the ability to grow deep taproots. These taproots allow the cacti in California to retrieve water from underground. Finally, their roots can shoot tiny trichomes that collect moisture from the soil when it gets wet.

Some species of cactuses, such as the ball cacti, have shorter roots that can also absorb water falling off the cactus.

The Stomata

Cacti have developed small pores on their surfaces called stomata that open up at night. When the pores open, the cactus absorbs moisture from the air along with the available carbon dioxide. This is a useful feature in the desert because its arid climate becomes more humid at night.

The stomata can efficiently gather as much water vapor from the air as possible. Although the stomata are not as efficient as the roots, it does help the plant boost its water reserves.

Conical Spines

The sharp and spiky conical spines on many cactuses serve as their defense mechanism against the hot, arid environment of the desert. Besides discouraging would-be predators from feeding on the cactus, the spines also create shade to protect them from direct sunlight.

And here’s the best part: the conic spines also help with water collection in several ways. One, the spines allow water condensation to build up on them, which is then collected by the plant.

Secondly, the spines also keep the cactus from losing its water reservoir. This is done by restricting the airflow around the cactus. The spines break up airflow, which reduces evaporation.

Introducing The Parenchyma Cell

Cactuses have a unique cell known as the parenchyma. These cells serve as a collapsible water storage facility of the plant and allow them to expand and contract. The flexible cell walls can develop when there is enough water intake and collapse when the water is released to other cells.

The presence of water softens the inner layer of the stem, often leading people to believe that cactuses are hollow. During rainfall, the plant’s roots collect water and transport them to the stem, filling the outer layers first before reaching the innermost tissue.

Cactuses will fill up every single parenchyma cell with water. This water reservoir is then stored in the event of a drought. During a dry spell, the cell releases all the water to the dried areas of the plant, including the chlorenchyma cells, to ensure that photosynthesis continues.

Cactus species from the driest parts of the world have massive stems to help them store as much water as possible. Examples include Ariocarpus, peyote cactus, and Echinocereus.

Water Storage Capability of Cactuses

You would be surprised to learn that certain cactus species, like the Saguaro, can store up to 1000 gallons of water. The saguaro has a unique pleated surface that allows it to expand to contain as much water as it needs.            

However, regular cacti, especially the ones that are grown indoors, can store anywhere from 10 to 100 gallons of water. The plant’s water-storing potential depends on its overall size. In this case, bigger is always better. A larger cactus in California can store a much higher volume of water.

How Long Can Cactuses Safely Store Water?

As mentioned earlier, some cactus species can store water for up to two years because they have a massive reservoir to drink from. However, the average indoor plant may not survive more than four to eight weeks without water.

In general, the amount of time that a cactus can store water depends on its species, the environment, and its size. The plants use less water when the temperature is cooler. Smaller plants can use up all the stored water at a much faster pace.

Cactus species have been observed to go dormant during the winter months when they don’t use any water. This is why it is recommended to reduce the watering frequency in the winter months to prevent overwatering.

Can You Drink Water from a Cactus

In most cases, the water from a cactus plant is not safe for drinking, especially on an empty stomach. In truth, cactus plants create a deadly cocktail of fluid that is composed of water, acids, and alkaloids.

The only way to safely drink this fluid is to refine and filter it. Chances are, if you’re desperately searching for water in the desert, you probably don’t have the means to filter out the fluid to obtain clean water.

It is simply not recommended to drink water from the cactus, especially when you are already dehydrated and weak as it is. Ingesting the water will force the kidneys to work harder to break down the fluid.

Moreover, drinking the fluid can lead to severe symptoms, including diarrhea, vomiting, and even paralysis (the last thing you want if you’re stranded in the middle of nowhere). But there are some species of cactuses that could come in handy. For example, the fishhook barrel cactus may provide you with a source of water with minimal side effects.

In any case, you should avoid drinking cactus fluid and find an alternative source of hydration.

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Wrapping Up – How to Do Cactus Store Water

So, there you have it, a detailed look at how the majestic cactus in California collects and stores water. Its unique root system, stomata, and spines allow the cactus to collect water. Meanwhile, the powerful parenchyma cells can expand and contract to accommodate varying volumes of water.

All these mechanisms ensure that the average cactus plant can survive several weeks (and even months) of dry spells in the desert. But just because your cactus can go without water doesn’t mean you should deprive it of hydration. Underwatering is the fastest way to kill your cactus in California.