Grow star cactus in full sun, in a mix that drains, and water when the mix is dry. These plants are Astrophytum, ribbed globes and columns from Texas and Mexico. A tag that says star cactus succulent is often a leafy Haworthia, not this cactus.
Give it full sun, a mix that drains, and water when the mix is dry
| Factor | Recommended | Avoid |
|---|---|---|
| Light | Full sun; light shade in the hottest afternoon | Do not keep it in a dim room if you want a tight body and flowers |
| Water | In growth, soak when the mix is dry, then let the pot drain | Do not keep the mix wet between waterings, especially in winter |
| Soil | Gritty cactus mix with extra pumice or coarse sand | Do not use packed potting soil that stays wet |
| Warmth | Keep it frost-free; a cool, dry rest in winter | Do not leave it wet in a cold room or outdoors in frost |
Star cactus wants a bright sill or a patio table in full sun, and a mineral mix that sheds water. [1] While it is growing, water when that mix is dry, then empty the saucer. The body pulls flatter and the ribs stand out when it is thirsty; a firm, full body does not need water. Keep the pot almost dry in winter. [2] Soft, collapsing tissue is usually rot from a wet mix, not a missed watering. Sow seed on How to Propagate Star Cactus.
How do I care for star cactus?
Give it full sun, a gritty mix with a drainage hole, and water only when the mix is dry. Keep it frost-free, and do not leave the mix wet in winter.
How often should I water star cactus?
In summer growth, soak the mix when it is dry, then let the pot drain. In winter, keep it almost dry and water only if the body wrinkles hard.
When does star cactus bloom?
It opens yellow funnel flowers from the crown in warm months, after a cool, dry winter. A wet, warm rest is the usual reason it skips bloom.
Keep it cool and almost dry in winter
This cactus wants a rest, not a freeze. Bring the pot indoors before nights turn to frost. Keep it bright, and stop watering while the room stays cool. A cool, wet mix in winter is the usual collapse. A windowsill rest that stays dry is safer than a wet porch.
Can star cactus stay outdoors in winter?
Only where nights stay frost-free and the mix stays dry. In a cold garden, bring the pot in before frost, keep it bright, and water less until spring.
Grow it in a snug, deep pot that drains
The usual home is a pot, a bright sill, or a patio table, not a wet garden bed. Roots run deeper than the small body suggests, so choose a pot about as wide as the cactus and deep enough for the taproot. A snug pot with a hole dries faster than a wide tub. Unglazed clay dries faster than plastic. Empty the saucer. Wait to size up until the roots fill the pot, often every two years.
- Choose a snug, deep pot with a drainage hole. Empty the saucer after you water.
- Fill it with cactus mix cut with pumice, coarse sand, or grit. Do not use packed houseplant soil.
- Set the plant no deeper than it grew in the nursery pot. Firm the mix around the body without burying the crown in wet mix.
- Wait a week before the first watering so any nicks on the roots can dry.
- Wait to move it into a larger pot until the roots fill this one. A jump into a deep, wet tub is the usual rot.
Can I grow star cactus in a pot?
Yes. Use a snug, deep pot with a hole, a gritty mix, and full sun. Empty the saucer. It is not a dim indoor foliage plant.
Not peyote, not a starfish cactus, and not bishop's cap on a woodland plant
Star cactus here is Astrophytum: a hard, ribbed globe or column, often dotted with white flecks. [3] sand dollar cactus is a tiny spineless disk, usually with eight ribs and a line of woolly areoles. It can be mistaken for peyote, which is bluish-green, softer, and lacks those white specks. Peyote also opens small pink flowers; this disk opens yellow flowers with a red-orange throat. [4] Do not collect wild plants.
bishop's cap is the spineless cactus sold as bishop's cap. Woodland bishop's cap is miterwort, a moist-shade plant — see How to Grow Miterwort. A tag that says star cactus succulent is often Haworthia, a leafy rosette, not a ribbed cactus. Sea urchin cactus on many shop pages is Echinopsis, a spined globe, not the spineless disk. Starfish cactus is Stapelia, a carrion flower with four-angled stems. monk's hood is the spined, taller kind in this group. Chin cactus and grafted moon cactus live on How to Grow Chin Cactus and How to Grow Moon Cactus. Pincushion care lives on How to Grow Pincushion Cactus. Barrel cactus is a much larger globe — see How to Grow Barrel Cactus. Goat's horn, Medusa's head, and other collector names belong to lists we do not carry, not extra kinds we grow.
Is this the same as peyote?
No. Peyote is a softer bluish-green globe without white specks, and it opens small pink flowers. This cactus is hard and flecked, and it opens yellow flowers.
If the body goes soft, move the pot into brighter light, let the mix dry, and water only when the mix is dry. Bring it in before frost.
FAQ
Do I prune it?
You do not shape it like a shrub. Cut off a dried flower, or cut out a soft, rotting piece so the rest stays dry. New growth comes from the remaining body.
Do you list goat's horn and Medusa's head?
No. This shop list is sand dollar, bishop's cap, the smooth bishop, and monk's hood. Other species names belong to collector lists, not extra cards we list.
Is it safe around pets?
It is not known to be toxic if eaten, but spines on monk's hood still hurt. Keep pets from chewing or rolling on it.
Is Echinocactus asterias a different plant?
No. Echinocactus asterias is an older name for sand dollar cactus, not a second genus to grow.
Related guides
Recommended plants
References
- [1] North Carolina Extension Gardener Plant Toolbox -
https://plants.ces.ncsu.edu/plants/astrophytum/ - [2] Gardener's Path -
https://gardenerspath.com/plants/succulents/grow-astrophytum-cacti/ - [3] Wikipedia -
https://en.wikipedia.org/wiki/Astrophytum - [4] Texas Parks and Wildlife Department -
https://tpwd.texas.gov/huntwild/wild/wildlife_diversity/nongame/listed-species/plants/star_cactus.phtml
This note is part of Astrophytum Guides.
More first-season notes by plant are gathered in How to Grow Guides.
Updated: Reviewed by Bosquelle Editors