There are many types of cacti, which are found in dry places and deserts. Cacti are succulent plants. Succulent plants are thick and fleshy for storing water. While all cacti are succulents, not all succulents are cacti. Cacti are unique because they have areoles – cushion-like bumps that cover the outside of a cactus. One or more sharp, pointy spines are attached to each areole. Spines are a type of modified leaf. Most cacti species have no true leaves. They do, however, produce flowers and fruit – which provide an important food source to desert animals.
Cacti are a diverse group. There are more than one thousand different species of cacti. Some look like a single rounded shape (like a barrel cactus). Others have complex, branching arms or pads (like a prickly pear). They can be as tiny as a grape or grow taller than a house.
Without further ado, let’s explore some of the types and groups of cacti in the United States:
The saguaro is the largest cactus in the U.S., with some of the older individuals reaching heights of 40-50 feet or more! While it is probably the best-known cactus in the United States, the mighty saguaro actually has a fairly small range and is native to the Sonoran Desert only. The saguaro is actually a keystone species of the Sonoran Desert. Cavities in the large trunks of these tree-sized, columnar cacti provide homes to animals. Their flower nectar and fruit are also food for many Sonoran desert animals. The saguaro cactus is a single species (Carnegiea gigantea).
Organ Pipe Cactus
A relative of the saguaro, the organ pipe cactus (Stenocereusthurberi) boasts an impressive size. This large columnar species can reach 10 feet or taller! You can identify an organ pipe cactus by its many stems branching out from a single point at its base. Organ pipe cacti are found in the Sonoran Desert, especially in Organ Pipe Cactus National Monument in Arizona. This cactus thrives in the heat and is quite sensitive to freezing temperatures.
Prickly pears are a group of cacti within the genus Opuntia. You can identify prickly pears by their branching, flattened pads. These pads are not leaves. But they do perform photosynthesis, like leaves. If identified and prepared properly, the pads can be a delicious food. The fruits of prickly pears are also eaten by both animals and humans. You will find prickly pears in many deserts. Some species of prickly pears grow outside of deserts too.
Chollas are a group of cacti within the genus Cylindropuntia . They are closely related to prickly pears and have a similar branching appearance, but their stems are cylindrical, not flattened. There are many species of chollas, such as the buckhorn cholla and the teddy-bear cholla (pictured). While some chollas look soft and cuddly from a distance, they are, in fact, covered in very sharp spines!
Hedgehog cacti belong in the genus Echinocereus. They grow in clusters and are quite small, usually under a foot tall. They have ribbed stems and a rounded shape with no branching. Hedgehog cacti are beloved for their beautiful and brightly colored flowers. You can see hedgehog cacti in deserts and dry regions across the southwest United States and Mexico.
Barrel cacti belong in two different cactus genera: Ferocactus and Echinocactus. They are named for their rounded, barrel-like shape. Species vary dramatically in size, with some barrels under a foot and others over 10 feet tall! They are found throughout the southwest United States and parts of Mexico.
Pincushion cacti belong in the genus mammillaria. Types of cacti in this genus are also sometimes called nipple cacti. Pincushion cacti are characterized by hooked spines and a very small size. Often, they are just a few inches tall. There are many species of pincushion cacti. You will find pincushions across Central America and Mexico. A handful of pincushion species have ranges extending into the southwest United States.
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References and Further Reading
- The American Southwest (n.d.). Cacti of West and Southwest USA. Available: https://www.americansouthwest.net/plants/cacti/index.html
- CactiGuide.com (n.d.). Notes for the Genus: Mammillaria. Available: https://cactiguide.com/cactus/?genus=Mammillaria
- DesertUSA (n.d.). Barrel Cactus. Available: https://www.desertusa.com/cactus/barrel-cactus.html
- Dimmitt, M. (n.d.). Cactaceae (cactus family). Arizona-Sonora Desert Museum. Available: https://www.desertmuseum.org/books/nhsd_cactus_.php
- Gauna, F. J. (n.d.). Prickly Pear (Opuntia basilaris P. Mill.). Plant of the Week. U.S. Forest Service. Available: https://www.fs.usda.gov/wildflowers/plant-of-the-week/opuntia_basilaris.shtml
- Gauna, F. J. (n.d.). Barrel Cactus (Ferocactus sp., Britt. & Rose). Plant of the Week. U.S. Forest Service. Available: https://www.fs.usda.gov/wildflowers/plant-of-the-week/ferocactus_sp.shtml
- National Park Service (2005). Ecology of the Saguaro: II. NPS Scientific Monograph No. 8. Chapter 5. Available: https://www.nps.gov/parkhistory/online_books/science/8/chap5.htm
- National Park Service (n.d.). The Organ Pipe Cactus (Stenocereus thurberi). Organ Pipe Cactus National Monument. Available: https://www.nps.gov/orpi/learn/nature/organ-pipe-cactus.htm
- North Carolina State University (n.d.). Echinocactus. Extension Gardener Plant Toolbox. Available: https://plants.ces.ncsu.edu/plants/echinocactus/
- Notes from the Road (2022). Types of Cactus in the Desert Southwest. Available: https://www.notesfromtheroad.com/desertsouthwest/cactus-species.html