How to Care for a Star Cactus (Astrophytum Asterias)

The Star Cactus or Astrophytum Asterias is a favorite of owners and cactus enthusiasts worldwide. It’s a spineless cactus with a very peculiar round, short and chubby look. It’s quite an easy plant to grow and care for and is well suited for beginners.

To grow and care for a Star Cactus, keep mind the following:

  • Use a simple ‘soak and dry’ watering cycle. Root rot is always a problem to avoid.
  • It prefers warm temperatures between 70º-80ºF.
  • Place it dry location, without too much humidity.
  • Well-draining soil will always be safest.  
  • Sunlight is well appreciated. Partial shade also helps when the sun is too extreme.

The appearance and coloring of this cactus is quite striking. It is generally green, covered with small white dots. Getting the plant from a nursery that grows the plants from the seed is always ideal. Read this guide to learn more tips and tricks to care for cactus gem properly.

Basic Caring Guidelines

Something to keep in mind before jumping into the caring details is that this plant is unfortunately endangered in its natural habitat. Thankfully, it’s a favorite of owners and has therefore survived as a house plant. There are several things to remember when learning how to grow and care for the star cactus; the basic guidelines can be divided into the following: 

  • Watering
  • Humidity and Temperature
  • Light
  • Soil


Like with other cacti, the ‘soak and dry’ method is the best. This method is quite simple. First of all, we want to wait for the soil to dry off completely. We want to check that the soil is dry. There are several ways to do this. Some owners like to use a chopstick or even a moisture meter to check for dry soil.  

Once the soil is dry, we may water at the cactus base until we drench the pot completely. There must be an appropriate drainage hole at the base of the pot. Once the pot is drenching and indeed leaking from beneath, the watering cycle is done. Now, it’s merely a matter of waiting until the soil dries off entirely and repeating the cycle.

Obviously, like with other cacti, watering is not really necessary during the dormant phase. The ‘soak and dry’ method, though, will be able to indicate when to water, if at all. As usual, checking to see if the soil is moist or dry will tell us if it’s time to give it another watering.


The astrophytum asterias is no different in this regard to other cacti: humidity is not ideal. Now then, it’s safe to say that this particular cactus is quite hardy. Average room humidity should not hurt it. Naturally, warmer and dry environments will serve it better.  


A well-draining soil mix is a good idea when potting the star cactus (astrophytum asterias). Like most cacti, root rot is something we want to avoid. In this regard, well-draining soil can make a significant difference.

When it comes to soil, it’s important to remember some pointers. The star cactus, like other similar cacti, benefits from sandy and porous soil. This is mainly because organic mixes may attract pests and increase the possibility of rotting of the roots. Moreover, such a porous mix will be fast-draining, and this is always a good idea when applying ‘soak and dry’ watering cycles, as we described above.


It’s important to remember that if the cactus is indoors, the plant will do well next to sunny windows. This cactus really enjoys sunlight and will achieve the best results with a steady provision of it. In other words, it’s important to provide the plant with at least a few direct sunlight hours. If this is not possible, some owners use LED lights to provide that extra amount of light needed. 

On the other hand, the star cactus does relatively well outdoors, as it loves bright and direct sunlight and it may therefore enjoy it. This plant well appreciates an ample provision of natural sunlight, about 8 to 10 hours per day. Access to partial shade is also beneficial if the sun is too extreme.  

Our cactus may be enduring too much sunlight if it starts becoming brown and yellow. Contrarily, if the cactus lacks sunlight, it’ll start lightening in color, from dark green to lighter shades of green. We must check for these signs and adjust appropriately, either by providing more partial shade or more direct light.


Ideally, we want to keep our cactus in a particular range of conditions. Temperatures of around 70ºF (21ºC) or above are ideal for this cactus. This is no surprise since these plants thrive under warm conditions, much like other cacti. 

During the dormant months, the temperature really shouldn’t drop below 45ºF-55F (7ºC-12ºC). If necessary, simply move the cactus inside during this time where it’s going to be better protected from extremes.

Also, it is worth mentioning that this cactus can stand pretty extreme conditions regardless. Some of these plants can withstand temperatures as low as 20ºF (-6.7ºC). This, is not ideal. If the cactus is outside and frosty/winter conditions are expected, it’s best to bring it inside.

Advanced Caring Guidelines


Fertilizing this cactus is best done from June to September. When it comes to fertilizing, diluted houseplant fertilizer during this growing season will do just fine. As usual, fertilizing during the dormant phase is not necessary.


At first glance, there is not much pruning to be done to a star cactus. Its shape is quite forbidding in this regard. When we talk about pruning, perhaps we should refer to, in this case, to pruning the roots when repotting. This may be necessary every few years.  


When it’s time to repot, there are some things to take into account. Usually, April is the best time to perform this task. This will give the cactus ample time to recover during the growing phase and warmer months. It’s important to note, however, that this cactus rarely needs repotting.

This cactus is actually quite a slow grower. Most owners find that they don’t have to worry about repotting before the two or three-year mark. Watch out for signs of weak growth, or perhaps take a look at the root system itself to see if the cactus would benefit from this procedure. It’ll seldom be necessary.


When it comes to propagating the star cactus, there are several things to remember. First of all, we need to take into account that in the case of this specific cactus, the only method of propagation is via seeds. A quick look at the cactus’ shape will show us that cuttings or plantlets are an impossibility in this case.

The simple seed method goes something like this: First of all, fill up a seed flat, keep the soil moist throughout as well. Once the plants are about half an inch tall, then we can think about transplanting them and creating new cacti.

Once we have these sprouts, it’s crucial that we move this to a place with adequate light provision and partial shade. When watering them, we must remember that these are very delicate plants. What we want to do is avoid overhead watering. Instead, it’s best to water them with some sort of misting.

Growing from Seed

When growing the star cactus, as pointed out above, we can grow it from seeds. We must simply place them on seed flats with soil mix. Most owners usually try to keep this particular soil moist until there is germination. Afterward, it’s ideal for moving them to a sunny place.

While caring for these little plantlets, it’s best to mist the soil, instead of regular overhead watering. This is because we want to protect the little growing plants.

Pest Prevention

As usual, like in other cacti and succulents, there are several things to watch out for. Amongst them are things such as the following:


In the case of mealybugs, for instance, there are several things we can do. Mealybugs are essentially small white and fuzzy, and take away the vitality of the cactus. Mealybugs can suck on the sap and even munch on the plant’s roots, really hurting our plants. 

To get rid of them, we must spray the cactus with water. This is sometimes a bit dangerous, though, and we may hurt the plant if we got at it too strenuously. A simple alternative is to rub some alcohol on the plant with a cotton swab and attack the pest this way.

It’s important that we check the roots of the plant as well. This is key to really give the plant a thorough cleansing from the mealybugs. If the roots indeed have mealybugs, it’s important to give these roots a good shower and repot the plant altogether in a new pot with new soil mix too.


When it comes to mites there are some things worth remembering. Brown patches are obviously a sign of their presence. It’s vital to give the patches a wash or even treat them with cotton swabs and rubbing alcohol to combat them.


Scale is another problem that must be dealt with decisively. Scale bugs usually have a rather tough exterior. Usually, washing them off with water is not going to be enough. It’s usually necessary to pick each one by itself. Rubbing alcohol, cotton swabs and water will do the trick.


The star cactus (astrophytum asterias) certainly produces flowers. They generally will appear from March to May every year. These flowers are about 3 inches (7cm) in size and yellow with an orange center.

Related Questions

Why is the star cactus endangered?

The star cactus (astrophytum asterias) is indeed endangered. It’s originally native to a sector of Texas and the Mexican states of Nuevo León and Tamaulipas. Its natural presence has diminished tremendously, however. Scientists have found that herbivory and different pathogens have significantly hurt the star cactus in its natural environment.

Today it’s mostly restricted to quite a small area in Texas and Tamaulipas. Its presence in the wild is very scarce. It has thankfully been a houseplant since the 1840’s and this has allowed it to survive.

Is the star cactus poisonous to humans or pets?

The star cactus (astrophytum asterias) is not generally considered toxic. Eating it, however, may be inadvisable, regardless.

What’s the difference between a Star Cactus and Starfish Flower Cactus?

The names of these cacti may actually be confusing. The star cactus (astrophytum asterias) is, as we’ve explained in this article, a small and plump cactus. The starfish flower cactus, on the other hand, is a succulent (not really a cactus, despite its name) which can produce flowers shaped like a star.

There are other characteristics of the starfish flower cactus which are worth mentioning. These are quite different to those which we have been examining in the star cactus (astrophytum asterias). The starfish flower cactus, for one, is actually quite stinky and attracts insects although it’s not a carnivorous plant.

How big does the star cactus (astrophytum asterias) get?  

The star cactus (astrophytum asterias) may grow to about 2 to 6 inches (5 to 15cm). It’s quite a chubby and small cactus actually. It’s important to remember that this cactus is not so much tall as it’s round. Indeed, it’s fairly common to find these cacti growing to only about 1 or 2 inches (2 to 5cm) tall but having a diameter from 2 to about 6 inches (5 to 15cm).  

Does the star cactus (astrophytum asterias) have other names?

The star cactus (astrophytum asterias) actually does have other names. It’s also called star peyote, sand dollar cactus or sea urchin cactus, amongst others.

Sebastian Moncada

I’m also a plant enthusiast and researcher. I’ve been privileged to have lived my whole life around the wilderness of Colombia and I’m happy to share everything I learn along the way. “Adopt the pace of nature. Her secret is patience” – Emerson.

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