Indoor cacti fall into two groups that need almost opposite care. Clemson HGIC separates the arid-climate (desert) cacti from the rain forest (jungle) cacti. Desert cacti want direct sun and a dry winter. Forest cacti such as the Christmas cactus grow on trees in the wild and burn in direct sun.

Before you buy, check which group a cactus belongs to. Then match it to your brightest window.

9 indoor cacti at a glance

Descriptions are from Clemson HGIC and NC State Extension. Sizes are given where the source gives them.

CactusFormSizeLightNotes
Mammillaria (pincushion)Desert; globe or short column, often clumping3–41 cm (1–16 in)Full sun or bright direct lightRings of small flowers; easy
Opuntia (prickly pear, bunny ears)Desert; flat padsBunny ears to 61 cm (2 ft)Full sunBarbed glochids; wear gloves
Echinocactus grusonii (golden barrel)Desert; barrel with gold-yellow spines—Direct sunClemson: good for beginners
Gymnocalycium (chin and moon cactus)Desert; small globeG. mihanovichii 5–8 cm (2–3 in)BrightFlowers young and often
Cereus uruguayanus (column cactus)Desert; upright blue-green column0.9–1.8 m (3–6 ft) indoorsDirect sunWhite flowers that open at night
Schlumbergera (Christmas, Thanksgiving)Forest; flat, jointed, spineless stems15–30 cm (6–12 in) tallBright, indirectNeeds long nights to flower
Rhipsalidopsis gaertneri (Easter cactus)Forest; flat stems with rounded scallops15–30 cm (6–12 in) tallBright, indirectSpring flowers; fussier
Rhipsalis baccifera (mistletoe cactus)Forest; thin, trailing, leafless stemsTo 1.8 m (6 ft) long indoorsBright, indirectWants steadier moisture
Epiphyllum (orchid cactus)Forest; flat, toothed, trailing stemsE. oxypetalum 2.4–3 m (8–10 ft)Bright, shaded from afternoon sunLarge, often night-blooming flowers

Desert cacti

Pincushion cactus (Mammillaria)

NC State describes Mammillaria as a genus of 147 species, many grown as houseplants. Plants are globes or short columns, single or clumping, and their funnel-shaped flowers often form a ring around the top. Clemson calls them a large group of small, free-flowering cacti that are easy to care for. It names the powder puff (M. bocasana) and the old lady cactus (M. hahniana), among others.

NC State recommends full sun or bright direct light, with some afternoon shade in hot weather. A cool winter dormancy at 7–13 °C (45–55 °F) encourages spring flowers. Let the mix dry completely between waterings, and stop watering during dormancy.

Prickly pear and bunny ears (Opuntia)

Opuntia grows flat, paddle-like stem pads. NC State warns that besides spines up to 7.5 cm (3 in), the areoles carry tiny barbed bristles (glochids) that irritate skin. Clemson notes they can hurt more than the large spines and are hard to see. Handle them with rubber or leather gloves.

Clemson calls low, mat-forming prickly pears very easy to grow. Bunny ears (O. microdasys) reaches 61 cm (2 ft) tall and wide, with velvety green pads and yellow flowers. NC State says indoor plants need plenty of sun and cooler winter temperatures to flower. For soft or shrivelled pads, see prickly pear overwatering vs underwatering.

Golden barrel cactus (Echinocactus grusonii)

Clemson describes an upright, barrel-shaped green body covered in heavy gold-yellow spines, with gold flowers. It calls this cactus good for beginners. Iowa State Extension features it among popular succulents for growing indoors.

Chin and moon cactus (Gymnocalycium)

Clemson describes chin cacti as small, compact plants suited to windowsills, flowering young and often. NC State gives G. mihanovichii as 5–8 cm (2–3 in) tall and wide.

The red, yellow or orange “moon cactus” is a mutant G. mihanovichii with no chlorophyll. NC State explains that it survives only because it is grafted onto a green host, usually Hylocereus undatus. It prefers bright, indirect light and 20–30 °C (68–86 °F). See moon cactus rootstock if the base starts to fail.

Column cactus (Cereus uruguayanus)

Clemson describes an upright, smooth blue-green cactus with brown spines, growing 0.9–1.8 m (3–6 ft) tall indoors. Its white flowers open at night. Give it the same sun and winter rest as other desert cacti.

Forest cacti

Christmas and Thanksgiving cactus (Schlumbergera)

NC State says these are epiphytes from the humid rainforests of southeast Brazil, quite unlike the cacti of desert regions. They need bright, indirect light and do not tolerate direct sun. Water every 1–2 weeks, or when the mix is nearly dry.

Clemson tells them apart by the stems. The Christmas cactus has smaller, smooth-edged segments, and the Thanksgiving cactus has toothed or jagged ones. NC State notes most plants sold today are the hybrid S. × buckleyi.

Flowering depends on darkness and cool nights. NC State recommends nights of 13–18 °C (55–65 °F) and at least 13 hours of uninterrupted darkness from mid-September to mid-November. Our Christmas cactus not blooming, bud drop and limp leaves guides cover the common problems. The Christmas cactus hub collects the rest.

Easter cactus (Rhipsalidopsis gaertneri)

NC State describes the Easter cactus as an epiphyte from southern Brazil, with star-shaped red, pink or white flowers between late March and May. Its flat stems have rounded scallops, unlike the Christmas cactus.

Keep it at 16–24 °C (60–75 °F), with cooler nights near 10 °C (50 °F) in late winter to promote blooms. Clemson recommends a cool, dry rest from December to late March, until buds form. NC State calls it more finicky than its cousins: it drops stem segments if over- or underwatered. See Easter cactus common problems.

Mistletoe cactus (Rhipsalis baccifera)

NC State describes a leafless, spineless cactus with thin, trailing stems like green spaghetti. Indoors it reaches 1.8 m (6 ft) long in a hanging pot. It wants bright, indirect light, high humidity and 16–27 °C (60–80 °F). It needs more consistent moisture than other cacti. Its stems pucker and go soft when it is thirsty.

Orchid cactus (Epiphyllum)

Clemson describes flat, fleshy, often deeply toothed stems with a trailing habit. The flowers are 15 cm (6 in) long or more, often sweet-scented and night-flowering, on plants 2–3 years old. Clemson gives a range of 7–21 °C (45–70 °F).

NC State’s queen of the night (E. oxypetalum) has white flowers 30 cm (12 in) long that wither by morning. It needs bright, indirect light, protection from afternoon sun, and a regular soak in spring and summer.

Care by group

From Clemson HGIC:

Desert cactiForest cacti
LightSouth or west window, several hours of direct sunBright but filtered light; direct sun can burn
Growing season18–29 °C (65–85 °F); water when the mix has dried slightlyWater more; never let it dry out completely in spring and summer
WinterRest at 7–13 °C (45–55 °F); water only enough to stop shrivellingHoliday cacti: less water from late September, nights 10–13 °C (50–55 °F) to set buds
MixEqual parts peat-based potting soil and coarse sand or grit2 parts peat moss, 1 part garden soil, 1 part sand
FeedingLow-nitrogen fertilizer (such as 5-10-5) monthly, June to SeptemberBalanced liquid fertilizer monthly in the growing season

Clemson names too much water, insects and mites as the main problems. Root and stem rot follow a mix that drains slowly or watering too often. Aphids, spider mites and mealybugs are the main pests. Never leave a cactus standing in water. If a cactus has gone soft, read why your cactus is soft or wrinkled before you water it.

Pets

The ASPCA lists Christmas cactus (Schlumbergera, with Easter cactus as an alternative name), mistletoe cactus (Rhipsalis), tree cactus (Opuntia species) and thimble cactus (Mammillaria fragilis) as non-toxic to dogs, cats and horses. NC State still warns that Mammillaria spines are sharp and that prickly pear glochids irritate skin.

Not every plant called a cactus is one. The ASPCA lists pencil cactus (Euphorbia tirucalli) as toxic to dogs, cats and horses because of its irritant sap.

References