Fairy Castle Cactus

Slow-growing and up to six feet tall, the fairy castle cactus is also known by its scientific name Acanthocereus tetragonus. The fairy castle cactus gets its name from the way its turrets resemble those of a castle. Other popular names for this cactus include barbed-wire cactus, triangle cactus, and night blooming cereus.

This stunning cactus is native to Central America, Mexico, northern South America, the Caribbean, and the southern United States. This unique cactus seldom blooms, although on occasion it will develop substantial white flowers.

This is a seriously cool-looking cactus, and it’s actually pretty easy to grow on your own at home! In this guide, we’ll break down some important information about the fairy castle cactus, as well as some tips on how to grow one in a garden or in a pot.

What is a Fairy Castle Cactus?

The fairy castle cactus is classified as Acanthocereus tetragonus. Under the genus Cereus, it has also been given the species name C. hildmannianus. The susbspecies of this plant can be a bit confusing in terms of botanical classification. The fairy castle cactus belongs to either the C. uruguayanus subspecies or C. monstrose subspecies, and there is little information available about the differences between the two. In general, fairy castle cacti are classified as simply Acanthocereus tetragonus.

The fairy castle cactus is often called the barbed wire cactus, the sword pear, or the triangle cactus. When in its smaller, more miniature form, it is referred to as the fairy castle cactus. However, this species in general is often referred to as the fairy castle cactus regardless of size or cultivar.

Anatomy of the Fairy Castle Cactus

Tall and columnar, the fairy castle cactus may grow to a height of six to 23 feet. Its stems are around three inches in diameter, dark green, and feature three to five angles. It has grey areoles that are spaced approximately an inch apart. The radial areoles have six to eight spines up to one inch in length, whereas the central areoles have one to two spines up to one and a half inches in length.

This species of cactus’s blossoms have a tube that is three to six inches long and five to eight inches in diameter. The pistils are creamy white, the inner tepals are a very bright white, and the outer tepals are greenish-white. From dusk till dawn, the blossoms remain open, luring in hummingbird moths and other beneficial pollinators. This species produces crimson, glossy fruits that are about two inches long.

The individual stems of this extremely spiky, very big, and thicket-forming cactus can reach a height of 10 feet or even more. This species’ blooms open at night and shut during the day. A few times a year, this cactus blooms for many weeks at a time. This cactus usually grows in dense, spiky thickets in coastal hammocks.

Fairy Castle Cacti Native Environment

The fairy castle cactus is indigenous to Mexico, Central America, the Rio Grande Valley, and northern South America. In the southern region of the United States, it can be found in Florida and Texas. It is particularly indigenous to central and southern Florida, the Florida Keys, and hot, dry coastal environments as well as thickets and sandy coastal habitats farther south into the Caribbean. In New Caledonia, this species has become invasive.

Fairy Castle Cacti Uses

Young stems of this type of cactus can be eaten as a vegetable either cooked or uncooked, while the fruits are edible and quite delicious. It is occasionally grown outside as a decorative or landscaping plant. Because of its lengthy arms, it is occasionally planted as a living fence in arid landscaping projects. This species’ smaller cultivar is often grown as a houseplant due to its diminutive size and unique form.

Fairy Castle Cacti Varieties and Subspecies

There aren’t many varieties and subspecies of the fairy castle cactus, and its classification itself is a bit inconsistent. That being said, we do know that the miniature cultivar of this species of cactus is referred to as the fairy castle cactus.

Colors of the Fairy Castle Cactus

The stems of this cactus are a dark or deep green. The spines are usually creamy-white but can appear slightly yellow or brown. The flowers of this species are usually white with a greenish hue, with red or orange centers. This species also produces fruits that stay fairly small but are a rich, vibrant red color.

What Will Make My Fairy Castle Cactus Bloom?

Sadly, indoor-grown fairy castle cacti seldom blossom. Cacti require ideal circumstances for growth in order to produce blooms, and members of the Cereus family typically bloom at night. Large, white fairy castle cactus blossoms typically don’t appear until the plant is 10 years or older.

If you recently bought a grown fairy castle cactus and notice that it has a flower, take a really close look at it. Most likely, it is a fake flower that has been attached to the plant to sell better. The imitation cactus bloom won’t need to be taken off because it will ultimately fall off on its own. But, if you want the plant to produce its own actual blooms, carefully follow the care instructions in this article to give it the best chance of flowering. Because this plant takes a long while to even be ready to blossom, all you really need is a little patience.

How to Propagate Fair Castle Cacti

Cuttings or seeds can be used to propagate this species of cactus. When planting the cuttings or seeds, select soil that drains properly. Many horticulturists like to use a specific mix of cactus soil and perlite. In this combination, you can also add coarse sand to improve drainage.

Propagating From Seed

You only want to get the seeds from this cacti’s overripe fruits. Avoid buying seeds online. After obtaining the seeds, clean them and allow them to air dry. Then, plant them in a soil combination that drains properly and regularly water them only when the soil dries up.

Keep in mind that weather is crucial to the success of your fairy castle cactus propagation. You may plant the seeds outside if the weather in your location doesn’t go below 32 degrees F, but it’s ideal to keep them indoors under grow lights.

Propagating From Cuttings

Cuttings from fairy castle cacti can be easily propagated. You can effectively multiply your cactus by following a few simple steps.

To begin, put on a pair of thick gloves to shield your hands from the cactus’ pointed spines. Cut a branch off of the parent plant with a clean, sharp knife. Once the callus has developed over the sliced surface, place the cutting onto a piece of paper towel and let it dry out for a few days.

After the cutting has dried, place it cut-side down in well-draining soil. You can also dip the end of the cutting in the rooting hormone, but this step is optional. Keep the container in a bright area that is not in direct sunlight and gradually move it to a sunnier area. Do not immediately water your cuttings in order to reduce the possibility of root rot or other illnesses. Water sparingly after waiting a few days, and only when the soil seems dry to the touch.

How to Grow a Fairy Castle Cactus

The fairy castle cactus is a slow-growing, low-maintenance plant that is suitable for novice gardeners. Search for cacti with tall, slender, and round trunks if you want to find this kind of cactus to grow at home. The trunks of this species usually develop in groups and are sold that way. Little spines that run longitudinally from the top of the trunk down its side and to its base can be used to identify this species at your local plant store.

Repotting and Transplanting a Fairy Castle Cactus

This cactus generally has to be replanted every two years to suit its extensive root system and rambunctious growth behavior. Transplanting is important and advantageous to the health of the entire plant when your cactus outgrows a small container, ideally in the warm season. 

Start by carefully removing the cactus from its pot. After that, break up the old soil from the roots and search for any evidence of rot or pests. Pruning the roots might be smart at this point; it’s very beneficial to the plant and promotes new development.

As you repot the plant, spread the roots out in a larger container and fill it with potting soil. To lessen the risk of overwatering and the potential for ensuing root rot, let the soil dry for a week or more before beginning to water moderately.

Pruning a Fairy Castle Cactus

Virtually all cacti do not need any trimming or pruning. But, if the stem starts to get brown, you’ll need to remove it. Cutting it off with sanitized scissors will prevent most diseases from spreading. Keep the wound dry so it can heal and form a callus.

This species of cactus’ body can sometimes rotate to one side, giving it a twisted and unappealing look that is not quite like a castle. This can happen because of how the cactus is positioned in relation to the sun. The stem of the cactus can twist to seek the sun if you give it too much shade. Prune that area off and position the entire cactus in direct sunshine to stop its twisted development.

Water Needs for Fairy Castle Cacti

While watering your fairy castle cactus, make sure the soil is fully dry between applications. Water until the soil is penetrated and the water accumulates in the drip tray below the pot. To avoid root rot, empty the surplus water that has accumulated in the tray. Grow the cactus in an unglazed clay pot to allow excess soil moisture to be wicked away from the soil and keep your beloved cactus’s roots dry.

Sunlight Needs for Fairy Castle Cacti

For the best results, choose a full sun or moderate shade environment. It is advised to give your fairy castle cactus six to eight hours of direct sunshine daily. If you move the plant outside, put it in full light, but keep an eye out for dehydration symptoms like color changes or stem shrinkage. Avoid low-light situations, which can lead to distorted columns and fading colors.

Soil Needs for Fairy Castle Cacti

Employ a well-draining soil mixture, such as cactus soil, when planting this species of cactus. You can create your own soil by mixing equal parts of perlite, coarse sand, and potting soil with peat. Add a one-inch layer of fine gravel to the bottom of the plant’s pot for improved drainage and root defense. 

Fertilizer Needs for Fairy Castle Cacti

Throughout the spring and summer, give your fairy castle cactus a monthly feeding of liquid fertilizer. You might want to dilute the fertilizer with water to avoid overloading your cactus with nutrients. As the cactus needs to become dormant throughout the winter, avoid fertilizing it altogether during this season.

Temperature and Humidity Needs for Fairy Castle Cacti

This species of cactus enjoys hot weather. They can be grown outdoors in USDA hardiness zones 10 and 11. Throughout the spring and summer growing seasons, maintain temperatures in the range of 64 to 79 degrees F. Avoid temperatures below 30 degrees F for the best possible fairy castle cactus care since the plant is not cold-hardy or frost-hardy. The plant can survive in humidity conditions that are typical for an indoor space, and they do not need excessive humidity. Place the cactus away from air conditioners and sources of drafts.

Pests and Diseases to Watch Out For

Infestation risks can be completely eliminated with proper fairy castle cactus care. Mealybugs and scale are common pests for this species, so watch out for them if your cactus is having trouble growing or looks like it has some body damage. With a cotton swab coated in rubbing alcohol, wipe the plant to get rid of pests if they are discovered early. Neem oil or an insecticidal soap must be used to treat full-plant infestations. The plant should be placed in quarantine, away from other plants, until the infestation is dealt with.

If you overwater your cactus or don’t empty the drip tray after watering it, it might get root rot. Using a pair of razor-sharp sterile scissors, remove any dark or mushy roots from the cactus after removing it from its pot. Repotting the plant in new soil will limit the bacterial spread if there is substantial decay. Pour a mixture of one part hydrogen peroxide and two parts water into the dry soil to treat the fresh soil of any potential fungi and bacteria.

Is It Hard to Grow a Fairy Castle Cactus?

Not at all! This particular cactus requires similar growing conditions as other cacti. If you’ve successfully grown other types of succulents and cacti in the past, you’ll have absolutely no problem growing this beauty! Just keep in mind that it is a slow-growing species and getting it to flower will take a lot of time and patience.

The fairy castle cactus is a truly special type of cactus. Few match its large, unique-looking arms that resemble a castle. Luckily, this isn’t a species that is difficult to care for. You can start growing your own fairy castle cactus at home with minimal effort!