Acanthocereus tetragonus-Triangle Cactus, Fairy Castle, etc., etc.

Acanthocereus tetragonus (‘Fairytale Castle’) on 9-13-18, #507-1.

Green Finger, Fairytale Castle, Fairy Castles, Barbed Wire Cactus, Etc.

Acanthocereus tetragonus ‘Fairytale Castle’

a-kan-tho-KER(SER)-ee-us   tet-ra-GON-us
Synonyms: Acanthocereus baxaniensis (Karw. ex Pfeiff.) Borg, Acanthocereus colombianus Britton & Rose, Acanthocereus floridanus Small ex Britton & Rose, Acanthocereus horridus Britton & Rose, Acanthocereus occidentalis Britton & Rose, Acanthocereus pentagonus (L.) Britton & Rose, Acanthocereus princeps (Pfeiff.) Backeb., Acanthocereus subinermis Britton & Rose, Acanthocereus tetragonus var. micracanthus Dugand, Cactus pentagonus L., Cactus prismaticus Willd., Cactus reptans Salm-Dyck ex DC., Cactus tetragonus L., Cereus baxaniensis Karw. ex Pfeiff., Cereus horribilis A.Berger, Cereus nitidus Salm-Dyck, Cereus pentagonus (L.) Haw., Cereus princeps Pfeiff., Cereus reptans Haw. ex Steud., Cereus tetragonus (L.) Mill., Cereus tetragonus var. minor Salm-Dyck, Cereus undulatus Pfeiff., Cereus vasmerii Young

Not to be confused with Cereus hildmannianus subsp. uruguayanus. They are two separate species with some common characteristics.

Acanthocereus tetragonus (L.) Hummelinck is also a correct and accepted scientific name. It was described by Pieter Wagenaar Hummelinck in Succulenta (Netherlands) in 1938. The species was first named and described as Cactus tetragonus by Carl von Linnaeus in the first edition of Species Plantarum in 1753.

The genus, Acanthocereus (Engelm. ex A.Berger) Britton & Rose was named and described as such by Nathaniel Lord Britton and Joseph Nelson Rose in Contributions from the United States National Herbarium in 1909. Georg (George) Engelmann and Alwin Berger previously named the genus in 1905 but put it in a subsection of Cereus. Actually, Engelmann probably named it at a previous date then Berger published the name with Engelmann’s description in the Annual Report of the Missouri Botanical Garden in 1905. (That’s why there is an ex between the two authors names).

Plants of the World Online by Kew currently list 14 accepted species of Acanthocereus (as of 10-18-19 when this page was last updated). That is up 2 since I last updated on 12-3-18.

There is a little confusion between Acanthocereus tetragonus and Cereus hildmannianus subsp. uruguayanus. When I first bought my Cereus hildmannianus subsp. uruguayanus it was unlabeled. I posted photos of it on a Facebook group and was told it was Cereus hildmannianus subsp. uruguayanus and they said the common name was Fairy Castles. Then, when I was doing research on the Acanthocereus tetragonus, I found one of its common names is Fairytale Castle… I am no cactus expert, but I do like correct information to pass on. If I am confused, then the information I pass on is also confusing. One of their pages about Cereus hildmannianus subsp. uruguayanus has photos of Acanthocereus tetragonus… Well, there are several websites that have photos of one with the name of the other. But, from experience having both, they look different. Both species in the wild grow very tall, but they apparently both have “miniature versions” or cultivars which is where the name Fairy Castles and Fairytale Castles comes from. These miniature versions appear to be monstrous forms.

The LLIFLE (Encyclopedia of Living Forms) says this in the description of Acanthocereus tetragonus cv. Fairytale Castle:

“Fairytale castle”, “Fairy castle” or “Green finger” cactus is the evocative name by which this common succulent plant is marketed and refers to the numerous vertical stems of different heights that resemble spires and turrets. This diminutive cultivars ‘Fairy Castle’ was discovered in cultivation and is a very popular plant often found in the succulent part of the box retail stores. Some expert classify the cactus as a monstrous form of Acanthocereus tetragonus (Acanthocereus floridianus), but the true self of this plant is controversial and some suggest that it may be a form of Cereus hildmannianus or even a dwarf form of Cereus hildmannianus subs. uruguayanus. Whichever scientific name is correct, the plant is a delightful cactus.”

I picked this Acanthocereus tetragonus up at Wagler’s Greenhouse in September 2018. I think I had one of these in 2015, which I think also came from Wagler’s which was also unnamed. I gave up most of my plants a few years ago, so out it went. So, I decided to bring this one home.


Acanthocereus tetragonus (Fairytale Castle) on 10-10-18, #519-1.

I always measure the cactus when I bring them inside for the winter. So, on October 10 (2018) this plant measured 3″ tall x 2″ wide.

Family: Cactaceae
Origin: The species is native to Florida & Texas in the United States, Mexico, northern South America, Panama…
Zones: USDA Zones (° F)
Size: Ummm… The species can grow quite tall in the wild, but the cultivar remains much smaller.
Light: Sun to part shade
*Soil: Well-draining soil. Potting soil amended pumice or perlite and grit.
Water: Average water needs during the growing season, barely in winter.

One website says their Acanthocereus tetragonus ‘Fairy Castles’ is 10 years old and it has only grown to 18″.

*There are a lot of potting soil recipes online and many people develop their own with experience and what is readily available. Read the ingredients on the bag and always start with a base of a reliable brand name potting soil. I always use either Miracle Grow or Schultz Potting soil because I can buy it in large bags. They also offer cactus soil in smaller bags with similar ingredients. I used 2 parts potting soil with 1 part additional perlite and 1 part chicken grit. After reading that cactus and succulent enthusiasts were recommending pumice in place of perlite and grit, I decided to try it. So, in late in 2018 I purchased a bag of pumice online from General Pumice. I have been using a combination of about 50% potting soil and 50% pumice with favorable results.

You can read my Cactus Talk & Update and Cactus & Succulent Tips to get my opinion about growing cactus and succulents.


Acanthocereus tetragonus on 11-29-18, #534-1.

We had a couple of warm days so I took the cactus outside for a photoshoot on November 29


Acanthocereus tetragonus close-up on 12-1-18, #535-1.

Acanthocereus tetragonus is a ribbed, five-sided, columnar growing cactus. The areoles produce short hair-like spines with small tufts of wool.


Acanthocereus tetragonus on 6-22-19, #593-1.

We made it through the winter and the potted plants have been enjoying the outdoors since about May.


Acanthocereus tetragonus at 4 1/2″ tall x 2 7/8″ wide on 10-11-19, #639-2.

I had to move the potted plants inside on October 11 because the forecast was calling for a “widespread frost”.  As always, I photographed all the potted plants one last time outside and measured the cactus and most of the succulents. The Acanthocereus tetragonus measured 4 1/2″ tall x 2 7/8″ wide. It was 3″ tall x 2″ wide last October 10. That’s pretty good and the offsets grew A LOT. The plant has been in full sun on the back porch all summer which is why it looks like it does. If it were in more shade it may not have changed color…

My Acanthoceus tetragonus companion is still fairly small so I am very anxious to see what it will do as time goes by. I will continue adding more photos and information.

I hope you enjoyed this page and maybe found it useful. If you have any comments, questions or suggestions, I would like to hear from you. Please click on “like” if you visited this page. It helps us bloggers stay motivated. 🙂 You can check out the links below for further reading. The links take you directly to the genus and species of this plant.


2 comments on “Acanthocereus tetragonus-Triangle Cactus, Fairy Castle, etc., etc.

  1. April Steph says:

    I just bought a succulent and the plant guide tells me it is a triangle cactus. So I am collecting info, trying to verify if the plant guide was correct. I enjoyed your post and found it helpful. Thank you

    Liked by 1 person

    • Hello April! I am glad you brought home a Triangle Cactus. They are pretty neat and I enjoy having one in my collection. I wish you great success with your new companion. Thank you for visiting and thanks for the comment!


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