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Fairy Castle Cactus Care

Learn about fairy castle cactus care. Fairy castle cactus, aka Acanthocereus tetragonus or Cereus tetragonus, is a charming small cactus with straightforward care requirements. Learn how much light it needs, what the best soil is, how to propagate it, and more with my guide.

Meet the fairy castle cactus!

I’ve been on a bit of a cactus kick lately—maybe you’ve noticed? That’s because I have a sunroom now! I have more light than I could have ever imagined having. So I’m expanding some of my plant collection to include some different cacti and succulents.

I actually got my first fairy castle cactus many, many years ago. I think it was from the plant section at Ikea. A dangerous gauntlet as you’re trying to make your way out of the Ikea Marketplace section to the checkout. It’s called a fairy castle cactus because the growth pattern of the plant’s branching columns look like turrets on a castle.

You can see it in the picture below. Yes, it’s one of those cacti that stores will glue fake flowers onto. And yes, I did think they were real and that I was really, really good at growing plants. I was so upset when I realized it was glue.

In general, cacti are pretty easy if you have enough light. So the fairy castle cactus is a pretty easy plant. Let’s go over its care requirements and talk a bit about what the plant is and where it comes from.

cutting board and plants on open shelving
I was so proud of these flowers. Sigh.

Ok, so what is the scientific name for the fairy castle cactus?

Fairy castle cactus is just the common name. I always like to try to get to the bottom of a plant’s true scientific name because I like knowing exactly what the plant is. It can help you determine its care requirements…and I just love knowing about how plants are related to one another!

I found a few names associated with the plant name “fairy castle cactus.” Here are the three most commonly used names:

1. Acanthocereus tetragonus: This is the name that I think is probably the most correct name. Maybe? I don’t know. Acanthocereus tetragonus is a cactus species native to Florida and some areas of Texas in the US—as well as areas of Mexico, Central America, the Caribbean, and South America. The miniature cultivar of this plant is commonly known as a fairy castle cactus. And it’s the one pictured throughout this post.

2. Cereus tetragonus: When you search Google for this, a Wikipedia result comes up for “cereus tetragonus” on the side. But when you click it, it is actually the page I linked above for Acanthocereus tetragonus. That’s because the page says that Cereus tetragonus is a synonym for Acanthocereus tetragonus. When you click the source for this, it takes you to the Integrated Taxonomic Information System record, which also lists Cereus tetragonus as a synonym. 

3. Cereus hildmannianus: This is a different plant. It is often confused for the fairy castle cactus because of its columnar structure. However, this plant gets much bigger and it has a different structure to its columns. It’s also native to South America.

fairy tale cactus in a gold pot

How do you take care of a fairy castle cactus?

Fairy castle cactus care is very easy to take care of. I find true cacti generally very easy to care for as long as you have them in the right soil and have access to plenty of light. It is a great plant for beginners and hobby collectors alike.

Can you grow fairy castle cactus indoors?

As I mentioned in the scientific naming section, fairy castle cactus is native to areas of Florida and Texas in the US, as well as Mexico, Central America, the Caribbean, and parts of South America.

And what do those areas have in common? Well, lots of things. But the one thing I’m getting at here is light. And lots of it! The fairy cactus prefers a lot of light.

It can even withstand full sun outdoors. However, if you’re growing it indoors, make sure to slowly acclimate it to the harsh outdoors sun. Even “full sun” through a window is less severe than full sun outdoors.

If you’re growing it indoors—which is very common—put it in your absolute sunniest spot. It’s rare that the plant will burn with indoor sun, but keep an eye on it. Rotate the plant every few weeks so it doesn’t grow lopsided toward a light source (like a window).

If you don’t get a ton of light, the plant still might do well in your brightest window. You could also consider adding a growlight to supplement the light, especially in the fall and winter.

Monitor the plant for signs of suffering from low light. These include fading, dull stems that may become leggy looking. If the new growth on your plant’s columns are noticeably thinner than the growth on the base of the plant…it’s probably asking you for more light.

fairy tale cactus stems

Why is my fairy castle cactus turning red?

Much like with many varieties of hoyas, the stems on a fairy castle cactus (or the leaves on a hoya) turning reddish-brown can be a sign of sun stress. This can be good or bad. I personally prefer to avoid sun-stressing my hoyas as I don’t love the look.

If you notice stems on your cactus turning reddish-brown, try shielding the plant from a bit of light. It will likely fade a bit to green with some time. And if it doesn’t, it probably won’t hurt the plant.

What is the best soil?

Any cactus or succulent soil will work just fine. These soil mixes come premixed with things like sand and perlite to discourage too much water retention and encourage quick drainage.

Outdoors, make sure to amend the soil with something well-draining and sandy if you don’t live in an area this plant is native to. I don’t put any type of cactus in the ground where I am though—more on temperature and climate requirements in a bit.

Acanthocereus tetragonus

How often should I water fairy castle?

The soil you choose is a critical part of your watering routine. Using a very well-draining soil ensures that your soil won’t retain too much water when you water the plant. Allow all of the excess water to drain from the pot’s drainage holes.

Then, here’s the best part—you can basically ignore the plant until the soil dries out completely. For a lot of my cacti and succulents, I get them on a schedule of watering every 7-10 days in the spring and summer, every 10-14 days in the fall and winter.

I get to a point of where I can pick up a plant and tell by its weight if the soil is dry. Getting to know your plants is the absolute best way to ensure you are giving them what they need.

Watering your plant too often (or using soil that retains too much water) will lead to root rot. Most people give their cacti and succulents too much water because they think they need it. They don’t 🙂

If you start to notice yellowing, mushy stems and branches, that’s a bad sign. If you notice blackening on the stems, that’s an even worse sign. And I’m sorry to say that the blackening stem is beyond saving at this point.

Below is a picture of my Peruvian Apple Cactus. I ordered a plant that arrived with three completely unrooted cuttings. One of them was already beginning to rot, and the rot quickly spread up the entire stem. I was able to save the other two stems, thankfully.

rot spreading on a peruvian apple cactus
rot spreading on a peruvian apple cactus

Temperature & humidity

As with many other types of cacti from hot areas of the world, fairy castle cacti like warm temperatures. Think about where they come from—they can withstand very warm temperatures. Lots of heat.

If your plant is going through a period of excessive heat, make sure to check the soil often. You may need to water the plant more often to help it withstand the heat wave.

It’s the cold that you need to think about. Fairy castle cactus plants are not frost tolerant. They will die if they are exposed to frost. And they will likely begin suffering if temperatures begin dipping consistently down into the 40s Fahrenheit at night.

Acanthocereus tetragonus in a gold pot
barbs on a fairy castle cactus stem

Growth rate & repotting

Fairy tale cactus plants grow at slow to moderate rates. Acanthocereus tetragonus can grow to be many, many feet tall. I’m talking anywhere from 6 to 23 feet tall, according to Wikipedia.

However, keep in mind that the fairy castle cactus cultivar is much smaller. It may top out at several feet tall, but it will take a while. And as the plant grows, the base and older parts of the stems will develop a brown, wood-like appearance and texture (this is called corking).

As a slow grower, you probably will need to repot this plant only every few years. Even if you don’t need to size the pot up, you’ll still want to refresh the soil to ensure you replenish nutrients every few years.

In the years where you aren’t repotting, you can consider a fertilizer designed for cacti or succulents. I generally don’t use fertilizers on my cacti and succulents, but that’s only because I’m generally lazy with fertilizers. 

fairy castle cactus stems

How often do fairy castle cactus bloom?

Fairy castle cactus blooms are usually a white-cream color. They occur only at night, beginning to open around dusk, peaking overnight, and beginning to close as the sun comes up. They attract hummingbird moths.

Generally plants will not bloom until they are relatively mature. However I have had some of my cacti bloom after owning them for only a few years. My night-blooming cereus “queen of the night” blooms like crazy all year.

The morale of the story? Take good care of your cactus. Watch it grow. It probably won’t bloom until it is relatively mature and established—aka several years. However, you might get lucky!

hand holding a fairy castle cactus in a gold pot

Are fairy castle cactus poisonous?

I could not find any definitive information from a primary or reliable source indicating that the Acanthocereus tetragonus plant is toxic or poisonous if ingested. However, each of the stems is covered in many very, very shark spikes. 

So even if the plant isn’t toxic, I highly recommend keeping this one away from kids, pets, and anyone else who might want to eat or touch it.

When you handle the plant, use thick work gloves. The barbs can easily pierce some thinner gardening gloves. I used gloves and a paper towel folded four times to break the tip off of a stem to propagate.

fairy castle cactus on shelving with other plants

Fairy castle cactus propagation

Now let’s talk propagation. Cacti are some of the easiest plants to propagate, which speaks to their ease of care, too. I recommend propagating a fairy castle cactus using stem cuttings.

You should take a cutting from one of two places. First, you can cut a small arm off of a larger stem. These are natural breaking points that are easy to cut off. See the first picture below.

Second, you could take a cutting at a natural point on a stem where the growth stops and starts. These areas are pretty obvious because the stems thin out before they begin growing another piece. See the second picture below.

branching growth on a fairy castle cactus
cut point for propagation on a fairy castle cactus stem

Whichever part of the cactus you take a cutting from, take it with a clean knife. Then let the cutting callus over for a few days. This is essentially what happens when you just sit it on a counter and let the cut end harden.

Letting the end callus over helps to prevent bacteria entering the plant, but it also helps to prevent too much moisture from getting into the stem when you put it in soil. So this is an easy but important step to take.

After a few days, plant the cutting in well-draining cactus soil. You can give it a little water so that you can lightly pack the soil in around the cutting to keep it standing up straight. But then wait until the soil dries out before watering is again. Just like you would any other fairy castle cactus 🙂

Acanthocereus tetragonus cutting for propagation
callusing end on a fairy castle cactus cutting

And that’s that! Your plant will likely take a while to root, but cactus cuttings (at least in my experience) have a pretty high rate of success with propagation. Just make sure to put them in a small pot with well-draining soil. Pop that sucker in a sunny window and let it ride.

For more similar propagation posts, you might want to check out my post on How to Propagate Prickly Pear Cactus pads, and my tips for Propagating Succulents From Leaves and Cuttings!

Fairy castle cactus care overview

Here is a brief overview of the most important care points I’ve covered in this post. Hoping you found it helpful!

  • Light: Bright light; direct sun through a window is fine, but you may want to slowly acclimate a plant to direct outdoor sun.
  • Soil: Well-draining cactus or succulent soil.
  • Water: When the soil dries out completely.
  • Temperature: Warm temperatures are best; not frost hardy.
  • Flowers: Night-blooming flowers that may take years to emerge.
  • Propagation: Through stem cuttings in well-draining soil.
fairy castle cactus stems

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collage that says fairy castle cactus care with pictures of the plant

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