How to Tell How Old a Cactus Is?

Cactus is one of the most diverse families of plants, with over 2,000 species and 139 genera.

These uniquely gifted plants have evolved for nearly 40 million years and are amongst some of the longest-living families of plants on earth.

What remains confusing for some botanists is how a cactus shows its age, making this arena a popular field of study.

However, through research, scientists have been able to create a list of characteristics that can determine or help predict the age of a cactus.

Why Is Telling a Cactus’s Age Difficult?

Unlike other plants, a cactus doesn’t have growth rings that usually help determine a plant’s growth.

Though cacti have vascular bundles made up of xylem and phloem tissues, their secondary growth rings may be absent due to the dry weather conditions they survive in.

Another incredible fact about cacti is that they can become dormant. Most cacti stop growing as soon as the temperature stops dropping during fall as they are adapted to their natural habitat, where they mostly observe only warm weather.

This change could also challenge a cactus’s age projection and growth patterns.

How to Tell the Age of a Cactus

Despite the challenges that arise when calculating or predicting a cactus’s age, here are four things that can determine the age of a cactus.

Each of these signs may show differently in different species of cacti, but scientists rely on these aspects to estimate a cactus’s age.

Height of a Cactus

It has been found that a cactus grows about an inch every ten years. As shocking as this might be, a cactus’s height can help estimate its age.

For doing so, grab a measuring tape and measure the tallest part of the cactus.

Do not mistake measuring the arms of a cactus, as they vary in size and can throw off your calculation.

Once you have the measurement of the cactus’s height, divide it by 10. You’d have an approximate age of the cactus.

Since the growth pattern of every cactus is different, scientists usually observe the height of a cactus before diving into the calculations.

Saguaro cacti are the tallest growing cactus species worldwide, found primarily in the deserts of Arizona.

The tallest Saguaro cactus recorded to date is a 158-year-old (estimated) plant that’s 78 feet high in the air.

Research on other species of cactus is barely conducted as the famous Saguaro species has been the center of attention for the past few decades owing to their abundance in the arid and semi-arid deserts of Arizona.

Amount of Rainfall

Another factor that scientists believe can help determine the growth patterns of cacti is the amount of precipitation these plants receive.

It’s generally observed that the dry, less rainfall desert regions have slow-growing plants.

In comparison, the deserts are situated in areas where the amount of rainfall is suitable for the cactus’s growth; the height of the cactus grows faster.

An example of slow-growing cacti is the famous elephant cactus, also known as the Mexican giant cactus, which grows in the drier regions of northwestern Mexico.

The plant only gets 3 inches of rainfall each year.

A well-known prickly pear cactus found abundantly all around South America receives tremendous rainfall and tends to outgrow its space rapidly.

The Number of Areoles

Areoles are one of the distinctive features of a cactus that help distinguish cacti from other succulents.

These are the bumps on a cactus from which a cluster of thorns or spikes grows.

Areoles tend to grow thorns vertically, column-by-column.

Apart from that, the youngest cluster of thorns would be situated at the top, whereas the cluster underneath is likely to be older.

Young thorns are also reddish in color, helping in identifying the age of a cactus.

The Number of Arms

This characteristic is the most disputed as some species may have different growth habits and patterns that make this characteristic useless for some cacti.

However, it is considered that the number of arms on a cactus determines its age.

These arms are a distinctive feature of columnar cacti and branch out of the stem of a cactus.

For instance, a Saguaro cactus’s one fully developed arm indicates a 100-year life. More fully developed arms show that the plant may be over 100 years old.

Signs of Aging in a Cactus

While the age of a cactus may be challenging to determine or calculate, you can certainly tell when your cactus starts showing signs of aging. You can look for eight signs in a cactus to determine its old age.


As discussed above, numerous species of cacti grow in height and tend to grow arms as they mature. Their younger versions may not have large arm structures branching out.

However, as they get older, their arms branch out and clump together in some species. Species that have pads grow a large number of pads instead of arms as they mature.


As your cactus plant matures, it’d undergoes the natural process of corking, where the stem of the plant goes brown and hardens.

This is a sign of maturation that all plants go through as it balances the plant as it starts getting heavier on the top.

This browning can look quite similar to fungal attacks and sunburns, so make sure you’re paying close attention and not confusing the two. Otherwise, your plant’s health can be in jeopardy.

Crown Formation

Though not common in all species, crown formation is another sign of maturation in a cactus.

These crowns either produce tiny spines and fuzzy hair or for species like Golden Barrel Cactus, they tend to grow flowers.

Rib Formation

Ribs are an important adaptation for numerous cacti species. Ribs tend to shrink during drought, containing and protecting the water inside the plant.

As a cactus matures, it continues to grow and form more ribs due to the increase in the need for water. Apart from that, the ribs also grow in size to take in more water.

For instance, a 40-50 years old Golden Barrel Cactus is likely to have prominent and more pleated ribs as compared to a younger one.

Hair Shed

Due to the harsh climatic conditions, desert cacti face an intense amount of sunlight daily.

To protect themselves from the UV rays, some species of cacti produce wool or hair on their body.

However, as the cacti mature, they shed this wool or hair, mainly at the base of the plant.

The top portion of the cacti becomes quite fuzzy and continues to provide protection to the plant.

Mature Spines

As discussed above, young spines are reddish in color and not too hard in texture.

However, a mature cactus would have solid spines that are prominent due to their darker shade. You can find these spines growing at the bottom part of the cactus.

Spines also age as the plant ages and become longer and more tightly packed. The dense population of spines on a cactus’s body helps protect the moisture in the cactus.

This adaptation is one of the essential growth habits in the cacti situated in dry desert regions.

Production of Flowers

A cactus needs suitable conditions to produce flowers.

However, despite the optimum temperature and other weather conditions, some species of cacti fail to show any sign of flower production until 2-3 decades.

Hence, a mature cactus would produce flowers every season if the conditions are right.

This sign may be confusing for the species that start reproducing flowers at a younger age.

Shrunken Base

As the cactus matures, the top part of the plant becomes heavier, which is balanced by the corking of the plant.

However, the heavy top often results in a shrunken base. This base isn’t soft but relatively rigid. The process occurs due to the increasing weight and can be taken as a sign of aging.


Cacti are uniquely adapted species of plants that learn survival in the deserts but continue to mesmerize biologists with their growth habits under normal weather conditions.

The age of a cactus is still a puzzle as the longer life span of these plants makes it challenging for scientists to identify how long the plant has been around.

Apart from that, the gap in the research on cacti is also a significant issue.

While some cacti species are being researched due to their abundance in the States, many species are being neglected.

However, the unique growth patterns of each species could be a hub of opportunities for genetic engineering in the years to come.

Despite that, the signs of aging and characteristics to determine the age discussed above can help you figure out the age of your cactus plant.

It may be challenging but observing the signs can help immensely in deciding which weather conditions work perfectly, the schedule of watering, and other care rituals and habits.

You can also quickly identify which changes are regular and which require your attention.

Cacti are resilient plants. But like any other plants, they need care. Knowledge is power, and some in-depth knowledge of your cacti would help you maintain your plants better.