How Does the Old Man Cactus Adapt to the Desert?

What Animals Eat the Old Man Cactus?

The cactus is a succulent plant with many resources! Growing in dry climates, where several months can pass without a drop of rain falling, the cactus has nevertheless adapted very well to its environment. Some cacti are able to store up to 3000 liters of water.

This large quantity of water is stored within the plant’s body, which consists mainly of thickened, fleshy tissue to protect it from the sun and from drying out. The most superficial layer consists of several cells that open only at night to allow for the escape of excess water.

These cells are then closed during the day, so that they do not lose any water during periods of intense sunlight.

Also, when the cactus is threatened by drought, it produces a mucus-like substance that is used to seal any cracks on its surface.

Skin and Spines

Its flexible body may expand to hold more water when it rains, and its thorns allow water to seep down to its roots. All of these features assist the plant to retain moisture. Additionally, it can defend itself from hungry animals thanks to its thorns.

Active at Night

The cactus must deal with photosynthesis as well as other challenges in order to survive in the desert. Plants absorb CO2 during the day through holes called stomata, then use sunlight to convert it into carbohydrates.
The heat in the desert makes it such that when the pores open in the middle of the day, some of the water the cactus has stored will evaporate.
The cactus waits for the night and its colder temperatures to open its pores and absorb CO2 in order to solve this issue.
After that, the plant waits till dawn to convert it into carbs.

Cactus Roots Collect Water Quickly and Efficiently After Short Rains in the Desert.

Desert cacti are found in desert regions with scant amounts of precipitation. Short bursts of rain are the norm when it rains. Cacti must therefore evolve to swiftly and effectively capture water before the moisture evaporates into the dry air in order to survive. Desert cacti’s roots have two features that make them capable of doing this.

Shallow Root Systems

Most desert cacti have an extensive system of shallow roots that extend near the surface of the ground, and some larger cacti, such as the giant saguaro, also have deep root that strengthens the plant and stores water.

The shallow root system allows cacti to absorb as much water as possible when it rains, as well as allowing access to small amounts of moisture that may appear on the surface due to fog, mist, or morning dew.

Temporal Root Hairs

Another interesting way that cactus roots use precious water and prevent water loss is by sprouting temporary root hairs when it rains. These root hairs grow rapidly, rapidly increasing the area of ​​the root system that is in contact with the soil.

In other words, when a rainy season approaches and there is plenty of water in the soil, the roots sprout these temporary root hairs, which are nothing more than thin extensions of the primary root system.

In one day they can grow as much as in a month, rapidly increasing the surface area of ​​roots in contact with groundwater or surface water. They do this by lengthening and forming new branches on existing roots.

All this happens before the rain falls, so when it does, it feeds these hairs with extra moisture. This prevents water from evaporating into the air and also prevents the plant from having to invest energy into maintaining these structures once they’re no longer needed.

The process only lasts for several days after each rainfall, but it allows the plant to temporarily store more water—sometimes even twice as much—as they would have if they didn’t have this ability.

Why Don’t Cacti Have Leaves?

Does the Old Man Cactus Ever Bloom?

One of the most striking adaptations of the cactus is the lack of leaves. Although not all cacti are leafless, leafy species are limited to a small number of cacti belonging to three rather unusual cacti groups: genera Pereskia and Maihuenia and subspecies of Opuntioideae.

Precisely because of the process of photosynthesis and the need to have pores to absorb carbon dioxide and release oxygen, cacti have lost the need for leaves.

Plant pores are called a stoma, and multiple pores are called a stoma. They open to absorb carbon dioxide and give off oxygen during photosynthesis, and they close when there is not enough sunlight.

CAM Photosynthesis Minimizes Water Loss

Cacti and many other succulents have evolved a distinct type of photosynthetic process known as Crassulacean Acid Metabolism, or CAM photosynthesis, in addition to switching the principal site for photosynthesis from the leaves to the stem. And the reason for this change is, once again, the reduction of moisture loss through the stomata.

CAM photosynthesis allows the plant to open its stomata at night when temperatures are lower and water evaporation rates are lower.

The plant stores carbon dioxide that it takes in the form of malic acid so that during the day it can carry out photosynthesis with the stored carbon dioxide and the couplings can remain closed.

Cactus Stems Are the Best Experts in Storing Water and Reducing Its Loss.

They can live in some of the harshest environments on earth and have developed ingenious ways to cope with them. The stem is what supports the plant and can reach heights upwards of 30 ft tall. It also helps store water, which is a necessity in dry climates.

The stems have evolved a number of fairly clever adaptations to arid, hostile environments. They store and save water by making use of both their distinct exterior surface characteristics and inside cell architecture.


The cortical layer, or cortex, of the plant stem, is an area within the outer layer of cells known as the epidermis, and the cortical layer of the cactus is unique among plants in that it has an inner region that serves as a water reservoir. where the walls of the water-retaining cells are thin and flexible.

These large cells fill with stored water and are then released into the cells that need it in times of drought. Also, in many cacti species, these special cortical cell walls are wavy rather than smooth, so the cells can collapse in on themselves and release water more efficiently.

These water storage cells in the stems of cacti are filled with mucus, a sticky substance found in many succulent plants that are very good at holding water and keeping it from evaporating. In cacti, these mucous cells are often lined up in canals.

Increased Cortical Layer

Cacti also have thicker cortical layers than any other plant. And this cortical layer differs even more from the bark of other types of succulent plants in its ability to transfer water and plant sugars produced by photosynthesis due to the vascular tissue distributed throughout it.

This means that the plant does not have to rely on a slower process of diffusion of vital substances from one cell to another. This transmission efficiency is what allows cactus stems to have such a large diameter and therefore store larger amounts of water.

Larger Amounts of Stored Water Help Protect Cacti from Extreme Temperatures

Fascinatingly, huge cacti like saguaros, which become over 90% water when fully hydrated, benefit from all that water by becoming more stable and defensive.
The heat absorbed by the plant tissue during the day raises the internal temperature a little, but the thermal inertia of the water keeps it from increasing as high as the lethal outer temperatures that can occur in the desert.
The interior heat is then gradually radiated away as the air cools at night, keeping the cloth from freezing during the chilly winter nights.

The Cactus Shapes Increase the Internal Volume.

Plants that live in desert climates, for example, have adapted to conserve water, which is scarce in a hot, dry climate. Since they can’t afford to lose much of their water through evaporation, these plants have evolved to store as much water as possible in their bodies.

This isn’t practical for a plant that does most of its photosynthesizing from the top down because too much water would impede light from reaching the leaves.

So cacti and other succulents grow in ways that provide as much internal volume as possible without exposing too much surface area to the sun’s heat.

Their thick stems act as storage units for water and their round shapes minimize the area exposed to sunlight.

Slow Metabolism Allows Cacti to Save Energy

Desert cacti have less green tissue that performs photosynthesis since they lack leaves to function as plant-growing plants. They are thus slow breeders. For various reasons, slow metabolism is one of cacti’s most crucial survival strategies in the desert, where conditions are harsh and unpredictable:

conservation of energy.

Cacti can concentrate on preserving the structures and behaviors that help them survive rather than wasting energy on creating the leaves that other plants require to promote rapid development.
Fewer needs.
Cacti are sometimes easier to grow and may thrive on fewer resources because desert areas frequently have low-fertility soils and little rainfall.

Long life.
Cacti are in it for the long haul, with a typical lifespan of 10 to 200 years! Thanks to their slow metabolism, they are able to survive longer, which helps the plant reproduce at some point.

The Spines Play a Vital Role in Protecting the Cacti and Collecting Water.

There are many sizes and shapes of these spikes. They can be firm and sharp, fine and hair-like, bristly, woolly, needle-like, spiny, straight, or curved. They can also be long or short. And their colors are different.

Some may argue that it is not true to say that cacti do not have leaves because the spines are actually modified leaves. 

However, cacti’s spines are remarkably different from conventional leaves in both look and composition, as they are made of stiff fibers that are primarily formed of dead cells as opposed to the living cells in green leaves that enable plants to create food. through photosynthesis.

Protection Against Loss of Green Tissue

A fairly obvious function of cactus spines is to protect the plant from predators. This may seem excessive, but this level of protection is crucial for the survival of the cactus. Because they have less green tissue and are so slow growing, animals biting off parts can cause significant delays in their growth, which could eventually lead to plant failure.

However, protection from predators is not the only way cactus spines help a plant survive harsh growing conditions. In fact, there are different types of cactus spines, and some of them do not have any deterrent function.

Surprisingly, cactus spines actually play several very important roles in helping the plant conserve water and protect itself from the harsh effects of the sun, and even help collect moisture!

Air Flow Regulation

Spines are one of the first things we notice about cacti. They’re an iconic feature of desert plant life. But why do they exist? No living thing exists purely by accident. Spines serve as a protective layer for cacti, as well as a means to regulate airflow and temperature around the plants.

Spines help cacti survive in the desert environment is by regulating airflow around the plant. By interrupting the flow of air, the spines create a layer of air, or what might be called a microclimate, which serves as insulation against changes in temperature and accelerated evaporation caused by hot air or wind.

Moisture Collection

The ability of spines to absorb moisture for the plant may be the most unexpected method that cactus assist themselves survive in the desert. When it rains, fogs, mists, or dews, the environment’s moisture condenses on the spines and drips to the plant’s base, where the shallow roots of the cactus absorb it.

The Importance of the Areola for Survival in the Desert

Therefore, the spines are modified leaves and grow from organs called areoles which are modified branches. Areoles are a recognizable feature of the cactus plant, which means that if a plant has areoles, it must be a cactus, and if it doesn’t have areoles, it can’t be a cactus. Areoles are small raised cushions from which thorns, flowers, and branches grow.

Areoles are a key adaptation of cacti because they have created clusters of spines that are very important to the survival of the cactus and can cover the plant with spines much more effectively than plants that grow spines directly from their stems.

The clusters of spines they produce can have central and radial spines, as well as different types of spines, often including many small hairs or tiny, vicious, prickly spines known as glochids.


Where does the old man cactus grow?

While they can go outside in USDA zones 9 and 10, they will do best if you bring them inside when temperatures drop below freezing. They need plenty of sun, so make sure that there is plenty of space for them on your windowsill or wherever else you plan to put them. It helps if they are kept away from fans and vents, as these will dry out their sensitive skin.

How long does it take for Old man cactus to grow?

The Old Man Cactus is a slow-growing, spiny cactus. It has red or yellow flowers that bloom at night.

Although it can take 10 to 20 years for this cactus to bloom, they are relatively low-maintenance and very long-lasting plants. They make excellent houseplants. However, they do have a few requirements that must be met to ensure their proper growth.

Light: They need bright light but not direct sunlight. If they receive direct sunlight they will turn brown and may die. Typically they grow best in east or west facing windows in your home with morning sun exposure.

How big does an old man cactus grow?

It grows well outdoors in Mediterranean climates. Old man cactus usually attains 6 meters (about 20 feet) before flowering and can grow to twice that height.

Can you touch an old man cactus?

The old man cactus is a spiny, columnar plant whose distinctive look and name come from its white, hair-like spines, which turn grayish as the plant ages. These white hairs often fall off in later years, making the cactus look even more weathered and elderly.

One should note that these “hairs” often hide the cactus’ sharp spikes and may break the skin if they are touched. These sharp spikes can cause inflammation and infection in humans, so they should be handled with care or avoided altogether. Besides this danger, however, there are other ways people can interact with old man cacti without getting hurt: they can be used as beautiful decorations for homes or gardens.

Why is it called Old Man Cactus?

Like an old man, it has white hair and a rather slow-paced growth. This Mexican cactus is so thickly covered with soft-looking white hairs that its columnar stem is often entirely obscured. The white hairs are hard to see on some plants, especially those growing in sandy soil or wintering outdoors.

This plant’s common name comes from its interesting appearance: the spines are short and very wide, giving the plant a “bald” look which makes it appear to have a head. In fact, this cactus was dubbed ‘Beelzebub’ by its discoverer, who thought that the baldness looked like the devil’s head.

In addition to their common name, they’re also known as “old man of the mountain,” “old man cactus,” and “devil’s backbone.”

How do you water an Old Man Cactus?

Old Man Cactus plants are easy to maintain once they are established; however, they can be difficult to grow from seed.

The first step to caring for an Old Man Cactus is making sure that the soil where it will be planted drains well. Once your cactus has been planted, make sure that you water it thoroughly only once per month during the growing season (which lasts from April until September).

In the wintertime, it should be kept in a very bright area with low humidity and no watering at all.

It prefers temperatures ranging from 50° to 60° degrees Fahrenheit and very little watering.

How does the old man cactus reflect sun rays?

The spines also prevent sunlight from reaching much of the plant’s surface — except for its white “hair.” An old man cactus does not have green leaves; it uses its long hair to reflect the sun’s light for photosynthesis. It also traps heat, so it enjoys warm temperatures. In fact, it cannot tolerate temperatures below freezing or direct exposure to sunlight during winter months or intense summer heat.

What is the scientific name for the old man cactus?

Cephalocereus senilis

Are there different types of Old Man Cactus?

Old Man Cactus, Bunny Cactus, Old Man of Mexico, White Persian Cat Cactus, Cactus bradypus, Cactus senilis, Cephalophorus senilis, Cereus senilis, Echinocactus staplesiae, Pilocereus senilis.


Anwar Hossain

My name is Anwar Hossain. I am a cactus lover, researcher, and cactus blogger.

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