Everything to Know About Fairy Castle Cactus

If you’re searching for a new plant to brighten up your windowsill, the Fairy Castle Cactus makes a great choice.

Attractive, easy to care for, and as suitable for novice gardeners as experts, this appealing succulent will make a great talking point for your home.

Fairy Castles Cactus

Alternatively known as night-blooming cereus, triangle cactus, and barbed-wire cactus (or Acanthocereus Tetragonus, if you want to get fancy), the Fairy Castle Cactus gets its distinctive name from its branches, which clump together in the shape of spires and turrets.

If you’re thinking of jumping on board the succulent bandwagon, here’s everything you need to know about how to plant, grow and care for a Fairy Castle Cactus.

What is a Fairy Castle Cactus?

The Fairy Castle Cactus is the mini cultivator of the Acanthocereus Tetragonus, a species of cactus best known by its common names of night-blooming cereus, barbed-wire cactus, sword-pear, and triangle cactus.

Close up cactus fairy castle

As you’d expect of a dedicated sun-worshipper, it flourishes in hot regions and is native to the sunny, coastal habitat of northern South America, the Caribbean, Central America, Florida, and certain regions of Texas.

Although it can be grown outdoors in suitable conditions, the cactus also makes a splendid (and very popular) indoor houseplant.

What’s Makes the Fairy Castle Cactus Unique?

All succulents have their unique selling points. In the case of the Fairy Castle Cactus, the main talking point (and the reason for its whimsical name) is the profuse number of upright, bright green branches emanating from its five-sided main stem.

As the branches grow and offset to form smaller branchlets, the overall effect becomes that of a fairytale castle…hence its unusual name.

The Fairy Castle Cactus can grow up to around a meter in height, forming hundreds of branches and branchlets over its lifetime. It rarely blooms (and never before the age of 10) but when/if it does, the flowers will be large, delicate, and either white or yellow.

Each of its branches is five-sided, with a line of short, creamy, bristle-like spines running along each ridge.

Although the stems are a vibrant green when young, they can become brown over time as a result of an aging process called corking.

How Long Can a Fairy Castle Cactus Live?

Cacti have incredibly long life spans, with some species living for as many as 200 years.

While the Fairy Castle Cactus is unlikely to live that long, you can still expect it to stick around for between 20 and 30 years in the right conditions.

As a general rule, most Fairy Castle Cacti hit maturity at around the 10-year mark, after which they might start producing flowers and fruit.

Although the cactus can grow to heights of 1 meter, it grows and matures very slowly, so don’t expect your 2-inch seedling to start reaching the ceiling anytime soon.

How to Care for a Fairy Castle Cactus?

The Fairy Castle Cactus is a low-maintenance, undemanding succulent that even novice gardeners should find easy to grow. But like all plants, it pays to be aware of the tips, tricks, and techniques that will keep your plant healthy for years to come.

If you want your Fairy Castle Cactus to thrive rather than simply survive, here are the key pointers to know.


When it comes to growing a healthy, robust Fairy Castle Catus, location is key. This is a plant that loves the sun and plenty of light. Place it in a dark spot with no access to sunlight, and you’ll soon be looking at a very unhappy plant.

For an indoor cactus, a sunny spot in front of a window is ideal. Plant the cactus in an unglazed clay pot with drainage holes at the bottom for the soil to breathe. The pot should be a little on the larger side to allow the roots to breathe.

Although most people choose to grow their Fairy Castle Cactus indoors, it’s also possible to grow it outdoors in the right climate.

As it’s not cold hardy, it does best in USDA zones 10 – 11. Plant it in a well-drained spot, with deep soil. Growing it in a raised bed can help support proper drainage.

As cacti dislike the cold and go dormant in the winter months, the ideal planting time is during spring after the last frost.


The ideal cactus soil is well-draining, compact, and properly aerated. The biggest threat to cacti is root rot, a condition caused by overwatering and excess moisture. A loose, grainy soil that facilitates drainage will help prevent any issues.

You can buy pre-made cactus potting soils in stores or make your own using 3 parts regular potting soil to 3 parts coarse sand/ grit/gravel and 2 parts perlite.

As cacti are sensitive to bacteria, avoid any problems by sterilizing the soil before use. The easiest way to do this is by heating the soil using a bain-marie.

Simply place the soil in a pot or glass container before adding it to a larger pot filled with water. Heat the pot until the water reaches boiling point. Turn off the heat and leave the soil to cool before using.


For the first year after potting, a Fairy Castle Cactus will not need to be fertilized. After this, they can be fertilized once each month from spring through autumn.

You don’t necessarily need a special cacti fertilizer, but a low-nitrogen content, water-soluble 5-10-10 or 10-10-10 fertilizer diluted to 1/4 strength is ideal. Avoid fertilizing the plant in winter when growth is dormant.


Most cacti prefer as much light as they can get, and the Fairy Castle Cactus is no exception.

If you’re growing the plant indoors, a sunny ledge by a south-facing window is ideal.

If your home isn’t as light as it could be, it’s worth investing in a full spectrum UV grow light. They’re readily available, affordable, and ideal for indoor plants that thrive in sunlight.

If a Fairy Castle Cactus doesn’t receive as much light as it needs, its branches may start to fade and become misshapen.

The only way to stop these symptoms from becoming worse is to find a sunnier spot for the plant. Ideally, Fairy Castle Cacti need at least 6 hours of full sun a day: if the sun tends to move around your home, consider moving the plant with it.

As Fairy Castle Cacti grow and bend in the direction of the light, rotate your indoor cactus weekly to keep it straight and well-shaped.

If you intend on growing a Fairy Castle Cactus outdoors, pick an area of the garden that receives full sunlight for as much of the day as possible. Avoid planting the cactus under the shadow of any trees or shrubs.


Fairy Castle Cacti might appreciate as much sun as they can get, but they’ve got very different feelings about water. Water your cactus too often, and it won’t be long before it starts to kick up a fuss.

Wet feet, standing water, and constantly wet soil should be avoided at all costs, even if the initial symptoms of overwatering (plump, juicy-looking branches and lots of new growth) suggest otherwise.

Although the plant may look healthy from the soil up, the root rot happening below the surface will be far from a pretty picture.

As the rot develops and begins to move up the stem, you’ll start to notice blackened stems and mushy, unhealthy-looking branches. At that point, very little can be done to save the plant.

Before you water the plant, check the soil. If it feels moist, let it dry out completely before you add any further moisture.

You can either test the moisture level of the soil by touch or, for a more accurate reading, by inserting a wooden stick (a popsicle stick will be fine) a couple of inches into the soil. If the end of the stick feels dry when you pull it out, it’s time for watering.

When you water the plant, water the soil rather than the branches. As cacti benefit from the “soak and dry” method of watering, make sure to give the plant a thorough soaking, adding enough water for the excess to start spilling out of the drain hole at the bottom of the pot.

As cacti are usually thirstier during the warmer summer months than in winter, it’s worth bearing in mind the seasonal differences in moisture requirements.

Although you should always test the moisture level of the plant rather than simply watering by schedule, you can expect to water the cactus once every 2-3 weeks in summer, depending on temperature and humidity levels.

In winter, once every 4-5 weeks should be sufficient. If the temperature drops below 50 degrees Fahrenheit, watering should be avoided.


The Fairy Castle Cactus is native to hot, arid regions where frost and sub-zero temperatures are unheard off.

As they’re neither cold-hardy nor frost tolerant, be mindful of the temperature.

If you’re growing the plant outside, either bring it indoors or protect it with a covering when the temperature gauge dips below 30 degrees Fahrenheit. If you’re growing it indoors, avoid placing it in a draft or in front of any air conditioning vents.


Pruning might be a pain, but if you want your Fairy Castle Cactus to look good and stay healthy, it’s a necessary evil.

Remove overgrown foliage with a pair of sharp, sterilized gardening scissors to improve airflow and allow the light to reach all parts of the plant. If you want some baby Fairy Castle Cacti, save the cuttings for re-planting.


Although the Fairy Castle Cactus is a slow-growing plant, it grows just enough to require occasional re-potting. Most plants will need to be repotted every other year, or whenever they seem to be outgrowing their original container.

Start by letting the soil dry out completely. Gently extract the plant from the pot and brush away any old soil clinking to the roots.

Remove any dead or rotted roots and apply fungicide to any cuts. Center the plant in its new pot and backfill with soil, gently spreading out the roots as you do. Wait a week before watering.

Pests & Problems

Although the Fairy Castle Cactus is an easy-going, low-maintenance plant, it will still need a little TLC to prevent any problems from occurring. Some of the most common issues faced by owners of Fairy Castle Cacti include:


The most common reason for a Fairy Castle Cactus to develop issues is overwatering.

Too much moisture over an extended period will make the roots of the cactus rot. Once that rot starts inching its way up the stem of the plant, most cactuses will struggle to survive.

Stop the rot before it happens by using well-draining soil, unglazed clay pots with drainage holes, and using the “soak and dry” method of watering (i.e. allowing the soil to dry out completely in between watering).

If you notice any blackish, yellowish branches, it’s a sign that the rot has spread. Cut off the discolored branches with a sharp pair of garden scissors and remove the plant from its pot to inspect the roots.

Remove the rotten areas of root and leave the plant to dry out completely before replanting it in fresh soil. Unfortunately, there’s no guarantee the plant will survive if the rot is extensive.

Pest Infestations

After overwatering, the second biggest enemy of the Fairy Castle Cactus is pest infestation.

Mealybugs, spider mites, scale insects, and aphids find the sap of the Fairy Castle Cactus irresistible.

Once they’ve drained it dry, they’ll move on to their next victim, leaving the plant to wither and weaken. Before they go, they might leave a white substance on the plant’s branches that, if left untended, can lead to fungal infection.

To stop pests attacking your plant, wipe or spray the leaves with neem oil or insecticidal soap. If you notice any substances left on the braches from previous infestations, wipe them away using disinfectant soap.

Fruits & Flowers

Some plants might be grown purely for their flowers, but the Fairy Castle Cactus isn’t one of them.

Flowering Fairy Castle Cactus

The main attraction of this particular succulent is its unique, fairytale shape. It does occasionally bloom, but the keyword here is ‘occasionally.’

Very few, if any, Fairy Castle Cacti produce flowers before they reach the age of at least 10 years old, and many don’t even after that.

If your cactus happens to be one of the rare flowering types, you can expect white or yellow flowers in summer.

The flowers, which open between midnight and dawn, have long, delicate petals with a dense white or yellow center.

If you’re growing the plant outdoors, you can expect the blooms to attract plenty of pollinators. Depending on where you live, this could include hummingbird moths, sphinx moths, bats, and bees.

Once the blooms have died back at the end of the summer, you might see reddish-colored, oblong fruits emerge in their place.

Each fruit measures around 2 inches (5 cm) in length and has a glossy, spiny appearance. If you intend to use the fruits for propagation or even eating, you can start to harvest them in autumn once they’ve reached their full size.

Uses & Benefits

The Fairy Castle Cactus is an incredibly good-looking plant, with enough visual appeal to add a ton of flair to any room it graces.

But even leaving aside its physical attractions, it’s an excellent plant to have around. Just a few of its benefits include…

1. Air Purification

Back in the ’90s, NASA completed a study on the air purification qualities of houseplants.

They choose some of the most common houseplants around at the time (which included snake plant, English ivy, and pothos) and published a report confirming that, as suspected, plants do indeed help purify the air.

That report ended up getting misinterpreted, with the result that many people think that only those houseplants tested by NASA filter the air. In fact, every plant does, simply by virtue of being alive.

So, if you want a plant that will create a taking point AND help you breathe easier, the Fairy Castle Cactus is a no-brainer.

2. Tasty Fruits

Although the fruits of the Fairy Castle Cactus are small, they’re also very tasty. Sweet and juicy, they can be enjoyed both raw and cooked. Some people have even been known to use them to make wine.

3. Edible Stems

It’s not just the fruits of the Fairy Castle Cactus that can be eaten. When the stems of the plant are young, they can be treated as a vegetable and eaten either raw or cooked.

Green stem and spines of Fairy Castle cactus

As the cactus has no glochids (the tiny spines you’ll find on other cacti like the Prickly Pear), it’s easy enough to prepare simply clean away the line of spines from the outermost part of each rib, remove the waxy covering, slice, and leave to air dry before serving.

The flavor is slightly tart but very satisfying. Stick to young stems only, as the older stems can be tough and fibrous.

4. Insomnia Cure

The spines of the Fairy Castle Cactus contain a mild sedative that’s said to make an excellent cure for insomnia…. although be warned, this might be one for the adventurous only.

How to Propagate a Fairy Castle Cactus?

Even if you’re brand new to gardening, propagating a Fairy Castle Cactus shouldn’t present any major difficulties.

Although you can propagate the plant from either cuttings or seeds, most people prefer to use cuttings due to the slow-growing nature of the plant.

That said, if you don’t mind a long wait, propagating from seed is perfectly viable too. Here’s how to do both.

Propagating from Seeds

If your cactus has already borne fruit, you can harvest them in autumn and use their seeds for propagation.

If it hasn’t (and don’t panic if that’s the case, Fairy Castle Cacti are slow to mature and won’t yield flowers or fruit until at least 10 years old, with some never or only rarely blooming even after that), seeds can be purchased online.

Sow the seeds in a well-draining soil made from 3 parts regular potting soil to 3 parts coarse sand/ grit/gravel and 2 parts perlite. Use an unglazed terracotta or clay pot with a drainage hole at the bottom. Avoid using any fertilizer.

Keep the soil moist, but not saturated, until the seedlings begin to emerge from the soil surface.

Once they’ve spouted, allow the soil to dry out completely before watering. Use the same ‘soak and dry’ method as you would for adult cacti to ensure the roots don’t rot.

As Fairy Castle Cacti are slow growers, don’t expect to see more than an inch or two of growth during the first year. If you don’t want to wait that long, consider propagating with cuttings instead.

Propagating from Cuttings

By far the most common and popular method of propagating Fairy Castle Cacti is with cuttings.

As the plants produce hundreds of branches and branchlets, you can cut off as many as you need without risking the look or health of the plant.

To start the process, grab a pair of sharp, sterile garden scissors and cut off a branch from the base of the plant. Allow the cutting to sit in the sun for a few days to let the wound heal and prevent bacteria from flourishing.

Prepare a well-draining unglazed clay pot with soil made from 3 parts regular potting soil to 3 parts coarse sand/ grit/gravel and 2 parts perlite.

If you want to give your cutting a head start, wet the base and dip it into rooting hormone to help speed up root formation. Plant the stem and place the pot in an area with direct sunlight.

If you use the rooting hormone, make sure the soil is moist when you plant the stem. After that, allow a few weeks for the stem to root before you start watering.

Propagating from cuttings is a much faster method than propagating from seeds, but even so, don’t be surprised if you don’t see much more than around 5 inches of growth during the first 12 months or so.