Popular Cactus Types for Indoors and How to Identify Them

Key takeaways

1. True cacti grow spines, flowers and shoots from fuzzy cushions called areoles; euphorbias have none and bleed milky sap.
2. Desert cacti such as golden barrel and Mammillaria need your sunniest window and a dry winter.
3. Christmas, Thanksgiving and Easter cacti are forest cacti: more water, less direct sun, and non-toxic to pets.
4. Bunny ears looks spineless, but its bristles detach at a touch; handle it with gloves.
5. Pencil cactus (Euphorbia tirucalli) is not a cactus and is toxic to cats and dogs.

How do you identify a cactus type?

Most cactus types sold for indoors fall into a handful of groups you can recognise by shape: flat pads, round barrels, small clustering pincushions, ribbed stars, columns, and the spineless "holiday" cacti with flat, segmented stems. This list gives each popular cactus its common and Latin name, how to spot it, how big it gets and one thing that keeps it alive. It also covers the plants sold as "cactus" that are not cacti at all, because one of them is toxic to pets.

First, a quick check that the plant really is a cactus. True cacti have areoles: small fuzzy or woolly cushions on the stem from which spines, bristles, flowers and new shoots grow. Spines come in clusters out of these cushions. Many succulents that look like cacti, especially Euphorbia, have no areoles, carry spines singly or in pairs, and bleed white milky sap when cut.

Popular cactus types at a glance

Desert cacti: the sun lovers

Bunny ears (Opuntia microdasys)

The flat pads look soft and spineless, but each dot is a tuft of tiny barbed bristles called glochids that detach at the slightest touch. NC State Extension advises wearing gloves. It is slow-growing and can eventually reach 60–90 cm (2–3 ft) tall. Give it full sun, a fast-draining cactus mix, and a cool, dry winter at about 10–18 °C (50–65 °F) with very little water. Brightly dyed pads sold in shops are a novelty, not a separate type.

Golden barrel (Kroenleinia grusonii)

The classic round cactus with bright yellow spines. Botanists have moved it from Echinocactus to Kroenleinia, so you will see both names on labels. It grows slowly, so a small barrel stays pot-sized for years. It needs the brightest spot you have; in weak light it stretches and the spines lose colour. Handle it with folded newspaper or thick gloves.

Pincushions: old lady and ladyfinger (Mammillaria)

Mammillaria is one of the easiest groups for a sunny windowsill. NC State Extension lists it as non-toxic to people and pets, though the spines (straight or hooked) can still injure. The flowers often form a ring around the top. The key to flowering is a cool, dry winter rest at about 7–13 °C (45–55 °F) with no watering, which encourages blooms in spring. Ladyfinger clumps fill a pot quickly and are easy to propagate from a broken stem.

Bishop's cap and old man cactus

Bishop's cap is a good choice where spines are a worry: it has none, just a neat star outline speckled with white flecks. Old man cactus grows into a hairy column; the white "hair" is actually modified spines with sharp ones underneath. Its hair can hide mealybugs, so check it closely. Both rot quickly if the soil stays wet, especially in winter.

Grafted and forest cacti

Moon cactus (Gymnocalycium mihanovichii)

The bright top is a colour form with too little chlorophyll to feed itself, so it is grafted onto a green cactus that does the photosynthesis. Keep it bright but out of the harshest midday sun, and expect it to be short-lived compared with ungrafted cacti. If the green rootstock rots, the coloured top goes with it.

Christmas, Thanksgiving and Easter cactus (Schlumbergera)

These are forest cacti from Brazil that grow on trees, so they want more water and less sun than desert types. Tell them apart by the stem segments: Thanksgiving cactus has pointed, claw-like projections on the edges, while Christmas cactus has rounded edges (NC State). Easter cactus has shorter segments with bristly tips and flowers in spring. Thanksgiving cactus needs at least 13 hours of uninterrupted darkness a night to set buds, so keep it away from lamps in autumn. The ASPCA lists Christmas and Easter cactus as non-toxic to cats and dogs.

"Cacti" that are not cacti: watch your pets

Pencil cactus (Euphorbia tirucalli) is a succulent spurge, not a cactus. The ASPCA lists it as toxic to cats and dogs: the sap irritates the mouth and stomach and can cause vomiting. Many other columnar "cacti" sold in garden centres are euphorbias too. Check for the clues above: no areoles and white milky sap. Wear gloves when cutting them and keep the sap away from eyes. If a pet chews one, call your vet or ASPCA Animal Poison Control.

Care that works for most indoor cacti

• Light: desert cacti want the sunniest window you have; forest cacti prefer bright light without hot direct sun. Signs of too little light are covered in signs your plant needs more light.
• Water: soak the pot, then let the mix dry completely before watering again. In a cool winter, desert cacti need little or no water. See how to water houseplants.
• Soil and pots: use a gritty cactus mix and a pot with a drainage hole. A soft, collapsing base usually means rot; our root rot rescue plan explains what to do.
• Handling: gloves, tongs or a band of folded newspaper protect your hands when repotting.

Not sure which cactus you have? Flori can identify it from a photo and show its care profile, including light, watering and toxicity. For more forgiving options, see our beginner plants that forgive mistakes.

Flori editorial team

Written and fact-checked by the Flori team. Every guide cites horticultural sources such as the RHS, university extension services and the ASPCA, and is updated when the advice changes.

General plant care information. Plants vary; when a plant is valuable or a problem spreads quickly, consult a local nursery or plant specialist.