Height or size of the cactus species
Every form of cacti has its own rate of growth, and there have been more than 300 genera and 3000 species identified.
To determine how much growth the species produces annually, we would need to study it for a number of years.
For instance, compared to barrel varieties, columnar types like the saguaro cactus grow taller. Older Golden Barrel cacti (Echinocactus platyacanthus) can reach heights of 8.2 feet (2.5 meters) and 5 feet (1.5 meters), respectively.
A Saguaro cactus (Carnegiea gigiantea) of a comparable age (about 100 years) can grow to a height of 15 to 16 feet (4.6 meters). The oldest Saguaro cactus ever measured, according to the National Park Service, rises more than 78 feet (24 meters) into the air.
The cactus can grow up to 8 inches (20 cm) per year, depending on its height and the growing environment (Drezner, 2003).
Regrettably, little research has been done on the age-size relationships of other cactus species. Since the Saguaro bloom is the state flower of Arizona and the cactus is protected, the Saguaro cactus is the subject of the majority of studies. The fact that the species is among the oldest and largest ever discovered on earth has also attracted a lot of attention.
Precipitation received
In addition to species, another element that affects cactus size is the amount of precipitation that cacti receive in their environment.
For instance, Pachycereus pringlei, which inhabits the western Sonoran coast and the Sonaran Desert’s driest regions like Baja California and receives little more than 3 inches of precipitation annually, develops exceedingly slowly.
In contrast, cacti from more humid habitats, such Opuntias or prickly pears from non-desert regions of South America, grow swiftly and have the potential to outgrow their surroundings.
Number of areoles
The quantity of areoles (plural: areola) also serves as a proxy for the age of the cactus.
A cluster of thorns (cactus-adapted leaves), blooms, and even a new branch or “arm” may sprout in an areola.
Less than a year old thorns are often reddish in color. The population increases column by column, with younger people at the top than the bottom.
Number of arms
The quantity of thorny “arms” sprouting off the main stem of columnar cacti can also serve as a proxy for the cactus’ age.
A Saguaro, for instance, must be at least 70 years old before it starts to sprout arms. It takes a saguaro at least 100 years to have one arm that is completely grown. It is most likely older than 150 years if there are multiple arms and blossoms.
However, other cactus species, like the Golden Barrel cacti, do not have branches.