Plant and Garden

Is the Fairy Castle Cactus an Acanthocereus or Cereus?

Fairy Castle Cactus is easy to care for. Making it one of the most commonly sold indoor cacti.

Experts can’t agree on the scientific names of this cactus. Is it Acanthocereus tetragonus, or Cereus hildmannianus? Is its subspecies uruguayanus, or monstrose? Most people simply prefer its whimsical common name Fairy Castle Cactus.

This common yet unusual plant is also known as (deep breathe in) Acanthocereus floridanus f. monstruosa, Cereus ‘Fairy Castle’, Cereus ‘Green Fingers’, Cereus hildmannianus f.monstruosus ‘Fairy Castles’, Cereus tetragonus ‘Fairy Castles’, Acanthocereus tetragonus cv. Fairytale castle, Acanthocereus floridanus f. monstruosa hort., Acanthocereus tetragonus cv. Fairy castle, Cereus cv. Fairy Castle, Cereus pentagonus, and Cereus floridianus. Whew, that is so many names!

Why So Many Names?

It seems there have been issues because plants are often reclassified. Scientific tools become more sophisticated. Our botonists and biologists learn more. And then they move plants to different genres and families.

Let’s Break It Down…

Cereus (KER-ee-us) hildmannianus (hild-man-ee-AH-nus) subsp. uruguayanus (ur-uh-gway-AN-us) is also known as Fairy Castles, Spiny Hedge Cactus, Peruvian Apple. This cactus is native to Brazil, Paraguay, Uruguay, and Argentina . 

Cereus hildmannianus was named and first documented by Karl Moritz Schumann in Flora Brasiliensis in 1890

Cereus uruguayanus was named and first documented by Roberto Kiesling in Darwinian in 1982.

However, the species was named and documented as Piptanthocereus uruguayanus by Friedrich Ritter in Kakteen Südamerika in 1979. BUT, somehow it was all screwed up and wasn’t an accepted name.

Cereus hildmannianus has the same range as the species as a whole and is usually spineless, unlike Cereus hildmannianus uruguayensis which is only found in Uruguay.

This Plant Has Multiple Personalities!

Some have the Cereus hildmannianus uruguayanus confused with the Acanthocereus tetragonu. When it is all said and done, scientifically they could be the same plant found in different regions.

Acanthocereus (Acan·​tho·​ce·​re·​us) tetragonus is a species of cactus that is native to the coastal hammocks and thickets of sandy coastal habitats in central and southern  Florida, the Lower Rio Grande Valley of Texas in the United States, Mexico, Central America, Caribbean, and northern South America.

Common names include Fairy Castle Cactus, Night-blooming Cereus, Barbed-wire Cactus, Sword Pear, Dildo Cactus, Triangle Cactus, and Órgano-alado de Pitaya.

The species was first named and described as Cactus tetragonus by Carl von Linnaeus in the first edition of Species Plantarum in 1753. Alwin Berger named the genus in 1905 but put it in a subsection of Cereus.  This is one reason these cactus get confused with each other.

Acanthocereus tetragonus (L.) Hummelinck is also a correct and accepted scientific name.

The Fairy Castle Cactus was moved to the genus Acanthocereus in 1938 by Pieter Wagenaar Hummelinck.

But the true self of this plant is controversial and some suggest that it may be a form of 
Peruvian Apple (Cereus hildmannianus).

Or even a dwarf form of 
Spiny Hedge Cactus (Cereus hildmannianus subs. uruguayanus).

The Fairy Castle Blooms

Or I should Say WHEN!

The Fairy Castle Cactus rarely blooms. Cacti need perfect growing conditions to produce flowers and the plants in the Cereus family bloom at night.

Click To Purchase The Fairy Cactus

Fairy Castle Cactus flowers are large and white and usually will not occur until the plant is ten years old or more.

The flowers are showy and are white with a deep red and orange or red-orange center. The flowers bloom at night and close during the day. This cactus blooms a few times a year for several weeks at a time

This highly spiny, often large, and thicket-forming, has stems up to 10 feet or possibly taller.

Fairy Castle Cactus Care

This cactus is a full sun plant that requires well-drained soil.

For best results, plant Fairy Castle Cactus in an unglazed clay pot that allows excess moisture to evaporate.

Place Fairy Castle Cactus in a bright sunny location that is away from drafts or air conditioning.

Water until the liquid comes out of the drainage holes and then allow the soil to completely dry out before watering. Overwatering is the easiest way to damage a cactus.

Click to purchase this Fairy Tale Castle pot for your Fairy Castle Cactus.

Fertilize with a good cactus fertilizer in spring when growth resumes. Feed monthly or with irrigation in a dilution that is half strength. Suspend the feeding in winter.

Click to read The Perfect Solution For Healthy Plants, where we share a homemade formula!

Propagation can be from cuttings. Cut section with a sharp blade. Allow the cut surface to callous over before planting in cactus soil. We recommend Miricle Grows brand.

You can also propagate using the seed. Allow unblemished fruit to ripen. Collect, clean and dry seeds. Unblemished fruit must be significantly overripe before harvesting seed. Sow directly into soil after last frost of the year.

We are not sure if we helped or confused you more. Whether you call your Fairy Castle Cactus an Acanthocereus or Cereus, this is a lovely plant that is easy to make part of your collection.


  1. Can you help me identify this cactus? It is growing out of control in Hawaii at the moment. Some say it is Peruvian apple cactus but the flowers are red so idk about that. Also heard this one isn’t particularly common. Thank you in advance.

    1. I am not an expert but I think that is a apple cacti monstrosa. Some people say it is a Peruvian cactus while others just say apple cactus.

      It is a night blooming Cereus repandus f. monstrosa. It would be invasive to Hawaii.

      The blooms should not be red. But being night blooming I think you are seeing the fruit. All Cereus cacti have edible fruit if there are enough pollinating bees in the area.

      The photos are HUGE! Very beautiful. I also see some sort of rat tail cactus in those photos.

      Thank you for the question. It is awesome to see what is growing on out there!

  2. My fairy cactus is soft. At first I thought it was under watered but even after watering it, it is still soft but green, no brown spots. Is it supposed to be soft?

Let us know your ideas and comments below!

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