Dog Tail Cactus vs. Dragon Fruit

Dragon fruit tree with ripe red fruit on the tree for harvest.
© iStock.com/HuyThoai

Written by Rebecca Mathews

Published: October 26, 2022

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Dog Tail Cactus vs. Dragon Fruit are very similar plants with long stems covered in short spines. They are both native to the Americas, but only one produces edible fruit. Can you tell the difference between them?

Let’s take a closer look at these two species of cacti.

Key Differences Between Dog Tail Cactus vs. Dragon Fruit

Dragon fruit tree with ripe red fruit on the tree for harvest.

Dragon fruit cacti have flat leaves with spikes and bear bright red or pink spiky fruit.

©iStock.com/HuyThoai

Dog tail cactus vs. dragon fruit are both vining cacti, but they look different after the first initial glance. The main differences are their foliage and the fruits they produce.

Dog tail cactus has more rounded foliage that’s covered in a carpet of thin fuzzy spikes, whereas dragon fruit plants have flatter leaves with a few spikes on the outer margins, and when it comes to their fruiting habit the difference couldn’t be clearer.

As its name suggests, dragon fruit has stunning edible dragon-like fruits that are egg-shaped, and red with green-tipped scales. Dog tail cactus fruits are not edible, and they are spherical and shiny black.

Dragon FruitDog Tail Cactus 
Scientific name(Selenicereus undatus)(Selenicereus testudo Strophocactus testudo, Deamia testudo
Common namesPitahaya, strawberry pear, Honolulu queen, Moonlight cactus, Queen of the NightPitaya De Tortuga
Native rangeNorth America, Central America, South America  South America
Height and Spread8–20 feet tall and 3–10 feet wide in the wild; several feet in cultivation10 feet tall by 10 feet wide in the wild; several feet in cultivation.
FoliageFlat, green; three spikes on each segmentRounded, green; covered with fine spikes
FlowersWhite with yellow insides; opens at nightWhite, orchid-like; opens at night
FruitEgg-shaped; red and green fruit with scales; edibleSpherical, shiny, and black; not edible
Growing Zone10–12 or houseplant7-11 or houseplant  
ToxicityNot toxicNot toxic

Dog Tail Cactus

The dog tail cactus (Deamia testudo, Selenicereus testudo, or Strophocactus testudo) is a cactus in the Cactaceae family. It’s native to the South American rainforest where it’s an epiphyte that grows on large trees, squeezing its way into the nooks and hooking around branches or rocks using aerial roots to grip on.

There have been many arguments over its classification, hence the collection of scientific names. The most recent classification in 2018 placed dog tail cactus in the genus Deamia.

It’s easy to see how it got the common name of dog tail cactus. It has long thin stems in the shape of — you’ve guessed it — a dog’s tail. There’s a similar cactus named rats tails which has thinner stems.

Dragon Fruit

Dragon Fruit

Dragon fruit has an unusual outer skin with green spikey scales.

©Pitchayarat Chootai/Shutterstock.com

Dragon fruit is both the name of the plant and the fruit it bears. It’s a cactus of the Cactaceae family, genus Selenicereus. Its botanical name is Selenicereus undatus and it’s native to the Americas, but experts are not certain exactly where. Some botanists consider it a natural hybrid.

It’s a vining cactus like the dog tail, that climbs trees and rocks using aerial roots and it’s called the dragon fruit because its fruit resembles dragon scales. Its fruit has bright red skin and green overlapping scales. It’s quite unusual and very tasty.

Growing Zones for Vining Cacti

Dog tail and dragon fruit cacti like warmth and indirect light. They make excellent house or conservatory plants but if you’re growing them outside dog tail suits Zones 7 – 11. Dragon fruit is less hardy and will only grow well in Zones 10-12.

Dog Tail Cactus vs. Dragon Fruit: Height and Spread

In its native environment, a dog tail cactus can climb, twine, and squeeze its stems to over ten feet in height and spread, but it doesn’t usually get this large in cultivation. Dragon fruit plants get a little larger. They grow in the same manner but natively can exceed 20 feet in length and 10 in width. Again, in cultivation, it usually reaches a few feet.

Both species are heavy because they retain water and get large, so if you’re growing one at home, be sure to construct heavy-duty support. Wild dragon fruit plants recorded at 25 feet can weigh a few hundred pounds.

How Does the Foliage Differ?

Both dog tail and dragon tail are creeping, climbing, and hanging vine cacti as we know, but they look quite different close-up.

Dog tail cactus has green rounded stems with ridges that are completely covered with brown fuzzy spikes, whereas dragon fruit foliage is flat with jointed green stems. Each stem has up to three short spines on each segment.

Both species tend to put on growth in mid-spring to late summer.

Dog Tail Cactus vs. Dragon Fruit: Flowers

Dog tail cactus has orchid-like flowers that are either white or pink and reach up to 12 inches in length, although those in cultivation are usually closer to four inches. They are very ornamental with a soft floral scent and appear from late spring until fall. This cactus is a night flowerer that’s pollinated by moths, so its blooms open during the evening and close by mid-morning.

Dragon fruit flowers are similar, but they’re more bell-shaped They appear in shades of yellowish-green and white with a yellow center and reach up to nine inches in length. They too are night bloomers pollinated by moths, but in contrast to the dog tail cactus, their scent is much stronger. Dragon fruit flowers are edible and only last for one evening!

Dog Tail Cactus vs. Dragon Fruit: Fruits

Dragon fruit cactus is well known for its gloriously weird fruits which are egg-shaped, red, and covered with overlapping, green-tipped scales. They certainly look like something from a medieval movie or outer space, but they are delicious and taste like pear and kiwi fruit. On the inside, they have white pulpy flesh studded through with tiny crunchy black seeds.

Dog tail cactus also has fruits. They are small, spherical, and shiny black but they’re not edible.  

Why Is My Dog Tail or Dragon Fruit Cactus Limp?

If your dog tail cactus or dragon fruit goes limp, it’s most likely due to too much water. Tip away any excess in the pot and let the roots dry out. You might be able to save it with quick action, but if the stems are mushy, it’s game over.

What Are the White Bits on My Dog Tail Cactus?

Dragon fruit cacti and dog tail cacti use aerial roots to cling onto tree bark or rocks and haul themselves up. Thin white bits waving in the air are usually these aerial roots.

If you see reaching aerial roots on your cactus, it can be an indication that your cactus needs a bigger pot or it’s not getting enough water or humidity.

The Honolulu queen cactus

Dragon fruit flowers only bloom at night.

©P. OCHASANOND/Shutterstock.com

How Much Light Do Dog Tail Cactus and Dragon Fruit Need?

In their native environments, both cacti thrive in bright but indirect light.

If you’re growing them outdoors, then the light shade of a tree or porch is a good place. Indoors, a conservatory or indirectly lit windowsill works well. Just be sure not to let direct light burn the foliage as this can lead to an infection that weakens the whole plant. If the stems are turning white, that’s a sign of too much light.

You’ll know if they’re getting enough light because the spikes will be short, upright, and healthy-looking. Too much shade and their spikes soften and droop.

Why Is My Dragon Fruit Plant Going Yellow?

When dragon fruits (or dog tails) have yellowing limbs, it indicates too much water. Stop watering and allow them to dry out. Both plants like fairly dry roots, but plenty of humidity. This is unusual for cacti, but because they are epiphytic they prefer to get liquid from the air.

Is Dog Tail Cactus or Dragon Fruit Toxic to Dogs?

The ASPCA lists dragon fruit as non-toxic to both cats and dogs, and it would be a brave animal that chewed on its partially spiky foliage.

Dog tail cactus isn’t toxic either and it’s even spikier, more than enough to keep inquisitive pets at bay!

How Do You Eat a Dragon Fruit?

Dragonfruit

Dragon fruit can be a chilly, refreshing snack.

©Poring Studio/Shutterstock.com

The best way to eat dragon fruit is raw. Cut it in half and use a spoon to scoop out the flesh in the same way you’d eat a kiwi or avocado. Here’s a top tip: if the dragon fruit is blue or pink, it’s not ripe. Wait until it’s blazing red with green only on its scale-like tips.

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About the Author

Rebecca is a writer at A-Z Animals where her primary focus is on plants and geography. Rebecca has been writing and researching the environment for over 10 years and holds a Master’s Degree from Reading University in Archaeology, which she earned in 2005. A resident of England’s south coast, Rebecca enjoys rehabilitating injured wildlife and visiting Greek islands to support the stray cat population.

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