With some species, you can guesstimate its years by height or width. This will be easier and more accurate with a houseplant cactus than with ones in the desert.
Cacti are some of the oldest plants with something like 2,000 species. In certain varieties, such as the saguaro cactus, it might be fun to know how old one is when you go to visit places like the Sonoran desert.
But determining how old taller cacti, like a saguaro cactus, won’t be the same for smaller, bulbous ones like a prickly pear cactus.
How Do You Determine the Age of a Smaller Cactus?
Although the estimate of one inch per 10 years is useful, it doesn’t apply to smaller cacti. This is because it’s better to know the growth rate of a particular species per year when it’s something like a barrel cactus or a prickly pear.
You can measure the size of the cactus and then calculate the relationship to how big it gets with maturity. But, more often than not, these will be about the width rather than the height that determines how old it is.
The shorter and rounder versions of cacti, like barrel cactuses, will continue growing throughout their entire lifespan. However, some varieties don’t get larger than about 3 feet tall.
Prickly Pear Cactus
A prickly pear cactus will grow up to 5 feet tall in its entire 20-year lifespan. They grow wider than they do tall, reaching about 10 to 15 feet. Also, an older prickly pear will have more cactus pads than younger ones. But finding out its exact years is iffy.
What about Cactus Houseplants?
When caring for a cactus as a houseplant, or in the garden, that you know has been around for a while, calculating its age will be easier.
The same guidelines apply to the different types above. As an example, one that grows upward measuring four inches will be about 40 years old.
Is Deciphering Age Different for Taller Cactus Plants?
For most tall cacti, their age often accompanies height. Measure the main body from the tallest point to the base. Multiply those inches by 10 years. This will give an estimate of the age of a cactus is, give or take a few years.
So, while you may determine a cactus is 95 years old by measuring at 9½ inches, it could be 100 years old or even 89 years old. as you can see, it’s merely a gauge to see the roundabout age of a cactus.
The Saguaro Cactus
The largest cactus plant in the united states is the saguaro cactus. The tallest ever recorded was in the sonoran desert of the saguaro national park in arizona at 78 feet tall.
These can take 100 years to grow 15 feet high. At 200 years, a saguaro cactus could very well be as tall as it will get, towering between 40 to 45 feet tall.
Saguaros have several spiny arms extending from the trunk, but the age comes from the tip of the central stalk.
This is often the tallest part, but not always. If the arm of a saguaro is taller than the central stalk, measure the tip down to the base. But, arms on saguaros are not a factor when determining age.
What Do the Arms Say about the Age of a Saguaro?
Some people believe a cactus with many arms determines age, but this is nonsense. The arms on a saguaro cactus have nothing to do with telling how old they are.
They Relate to Height
Saguaro’s arms relate to their height and maturity. Their genetics determine when arms should grow and it’s often after they’ve been alive for a great many years.
These are where most flowers appear and help the plant propagate. For instance, if anything happens to the main stalk of a saguaro, you can repot the arms to grow a new cactus plant. It will develop its own roots and continue growing.
How Old Are Cactus with Arms?
The saguaro cactus can have their heights reached by 95-100 years old. By 200 years in age, the height reaches about 45 ft tall and might produce one or more arms.
Normally, the oldest arms are those that don’t bud from the main stalk. Instead, they grow out from another arm and roots sometimes form at the junction of these two branches.
It’s almost impossible to know how long a saguaro cactus has been living in the sonoran desert, but a cactus houseplant is easier. Most cacti that grow upward will show their age by inches of growth per 10 years.
A measuring tape helps here, but it is going to depend on the cactus itself. Not all of them follow this guideline, like prickly pears and barrel cacti. But the saguaro cactus does.