Here's the plain-English tour, the same one we give customers walking through our own greenhouses in Fallbrook.
First, what makes a cactus a cactus?
All cacti are succulents, but not all succulents are cacti. The thing that makes a cactus a cactus is the areole, a small cushion-like bump the spines, flowers, and new branches all grow from. If a spiny plant has areoles, it's a cactus. If it just has spiky leaves or sap and no areoles, it's something else (more on those impostors below). Almost all cacti are native to the Americas, and almost all of them are built for the same job: storing water and surviving drought.
The eight types you'll actually meet
1. Barrel cacti (the round ones)
Squat, ribbed, and roughly ball- or barrel-shaped. This group includes the famous golden barrel and the red-spined Ferocactus. They're slow, sculptural, sun-loving, and about as low-drama as a plant gets, which makes them a great first cactus. Browse our barrel cacti to see the range.
2. Columnar cacti (the tall ones)
Upright pillars that grow toward the sky. This is where the showstoppers live: San Pedro, the giant cardon, the Argentine saguaro, and the powder-blue blue torch. Some stay knee-high, others tower over a house given enough decades. If you want a cactus that makes a room or a yard feel like the desert, start with our columnar cacti.
3. Pincushion and globe cacti (the little clustering ones)
Small, round, and often growing in tidy clusters, usually crowned with a neat ring of flowers. The huge Mammillaria group lives here, along with plants nicknamed old lady cactus, snowball cactus, and rainbow pincushion. They stay compact, flower young, and are perfect for windowsills and desks. See our Mammillaria collection.
4. Prickly pear and pad cacti (the flat ones)
The Opuntia group, instantly recognizable by its flat, paddle-shaped pads stacked one on top of another. Many are cold-hardy, many produce edible fruit and pads, and they range from ground-hugging spreaders to shrub-sized. Bold, easy, and unmistakable.
5. Cholla (the jointed ones)
Close cousins of the prickly pears, but built from cylindrical, jointed segments instead of flat pads. Chollas have an almost architectural, branching look and spines that catch the light. Sculptural and tough, and a favorite for desert landscaping.
6. Old man and hairy cacti (the fuzzy ones)
Columns and clusters wrapped in soft-looking white hair, which is actually modified spines that shade the plant from harsh sun. Old Man of the Andes, the Peruvian old man cactus, and the monkey tail all belong here.
7. Star and living-rock cacti (the oddballs)
Spineless or nearly spineless, low, and geometric. Astrophytum, the star cactus, looks like a segmented green starfish pressed flat to the soil. These are collector favorites for their strange, almost man-made shapes, and they stay small their whole lives.
8. Forest and trailing cacti (the rule-breakers)
The one group that breaks the desert stereotype. Christmas cactus, rhipsalis, and their relatives come from humid forests, not deserts, where they grow on tree branches. They trail rather than stand, they like a bit more water and a bit less blazing sun than the others, and they bloom in a big seasonal show. If a "cactus" is soft, leafy-looking, and hanging from a basket, it's almost certainly one of these.
Plants that look like cacti but aren't
No areoles, so no cactus
- Euphorbias (like the firestick or the African milk tree) mimic cactus shapes but ooze a milky, irritating sap when cut.
- Agaves and aloes are spiky succulents with fleshy leaves, not stems, and grow in rosettes.
- Snake plants and yuccas are stiff and sword-leaved, and not cacti at all.
It's not a problem to grow any of these, just know that their care can differ from a true desert cactus.
How to pick your first cactus
New to cacti, or tight on space
- Barrel cacti: slow, sculptural, forgiving.
- Pincushions: compact, flower young, happy on a windowsill.
Want more of a statement
- Columnar cacti: tall pillars for a corner or a yard.
- Forest cacti (like Christmas cactus): the pick for a shady indoor spot where desert types struggle.
Whatever you choose, the care rule is the same across almost all of them: bright light, gritty fast-draining soil, and water only when the soil is bone dry.
The quick version
- Cacti sort into about eight shapes: barrels, columns, pincushions, pads, cholla, hairy old-man types, star cacti, and trailing forest cacti.
- The areole (a little bump the spines grow from) is what makes a cactus a cactus.
- Euphorbias, agaves, and aloes look the part but aren't true cacti.
- Beginners: start with a barrel or a pincushion. They're the easiest to keep happy.
- Nearly all of them want bright light, gritty soil, and water only when fully dry.
Once you can name the shape, the rest of cactus care gets a lot less intimidating.