My Neighbor Gave Me a Bag of These Strange Black “Horned” Nuts — What Are They and How Do You Eat Them?

At first glance, these unusual black fruits look more like tiny animal horns or something from another planet than something you would put on your dinner plate. But they may actually be water caltrops, an edible aquatic fruit with a surprisingly long history of use as food.

When someone hands you a bag filled with strange, dark, sharply pointed fruits, the first question is probably not “How should I cook these?” It is more likely to be “What on earth are these things?”

The fruits shown in the image have a distinctive shape: a hard, dark outer shell with curved projections that resemble horns. They are commonly associated with water caltrops, fruits produced by plants in the genus Trapa.

Depending on the species and region, they may be called water caltrop, buffalo nut, bat nut, devil nut, or water chestnut. Despite some of these names, they are not the same thing as the familiar Chinese water chestnut commonly found in canned Asian vegetables.

That distinction matters.

What Are Water Caltrops?

Water caltrops are the fruits of aquatic plants that grow in freshwater environments, including ponds, lakes, and slow-moving waterways.

The plant floats on or near the surface of the water, producing rosettes of leaves. Beneath the surface, it develops fruits with an extremely hard outer shell.

The unusual shape of the fruit is one of its most recognizable characteristics.

Some varieties have two prominent horns, while others can have three or four projections, depending on the species.

Those sharp structures aren't just decorative.

They help the fruit anchor itself and may also discourage animals from eating or disturbing it before the seeds are ready to germinate.

Once you see one, it's difficult to forget it.

They look almost like miniature medieval weapons.

Is the Inside Actually Edible?

Yes, certain water caltrop species are traditionally eaten.

The part people consume is the starchy kernel inside the hard shell.

The exterior can be extremely tough, woody, and difficult to open. That's why these fruits are generally cooked first and then opened rather than eaten like ordinary nuts.

Inside, the edible portion is usually pale or whitish.

Its texture is firm and starchy, and people often describe the flavor as mild, slightly sweet, earthy, or reminiscent of a chestnut.

This is why water caltrops are sometimes compared with other starchy foods even though botanically they are quite different.

How Are They Traditionally Prepared?

One of the simplest methods is boiling.

The whole fruits can be washed and cooked in water until the interior becomes tender.

After cooking, they should be allowed to cool enough to handle safely.

The hard shell can then be cracked open using an appropriate kitchen tool.

A sturdy nutcracker, heavy kitchen shears, or another suitable tool may work depending on the fruit.

Do not try to bite through the shell.

Those projections can be surprisingly sharp, and the shell itself is far too hard for normal eating.

Once opened, the pale interior can be removed and eaten.

Some preparations also involve roasting or steaming the fruits.

In regions where water caltrops are traditionally consumed, they may be incorporated into various dishes or eaten as a simple cooked snack.

Why Shouldn't You Eat Them Raw?

This is probably the most important point if you've received a bag of these from someone who harvested them personally.

Don't assume that a freshwater plant is automatically safe to eat raw.

Aquatic plants can come into contact with microorganisms, parasites, contaminated water, mud, and other environmental contaminants.

Historically, raw consumption of certain freshwater plants has been associated with parasitic infections, particularly in regions where specific parasites are endemic.

Cooking can substantially reduce the risk from many biological hazards.

That doesn't mean cooking makes an unknown plant automatically safe.

If you don't know where the fruits came from, how they were harvested, or whether they were correctly identified, don't eat them simply because they look like the ones in a photograph.

Proper identification matters.

Water Caltrop vs. Chinese Water Chestnut

Here's another common source of confusion.

The name “water chestnut” is sometimes used for water caltrops, but Chinese water chestnut is actually a completely different plant.

Chinese water chestnut, Eleocharis dulcis, is a grass-like aquatic plant whose underground corms are commonly eaten in Asian cuisine.

Those are the small, round, brown-black vegetables you may recognize from stir-fries and canned foods.

Water caltrops, on the other hand, are the horned fruits shown in this image.

So if someone tells you, “They're water chestnuts,” it's worth asking exactly which plant they mean.

What Do They Taste Like?

The flavor is generally fairly subtle.

The cooked kernel is starchy rather than juicy, with a texture that can remind people of chestnuts or other firm cooked roots and seeds.

That's part of their appeal.

They don't necessarily have a powerful flavor on their own, which means they can work well with seasonings and other ingredients.

Depending on the cuisine, cooked water caltrop kernels may be served simply or incorporated into larger dishes.

Some people enjoy them because of their satisfying texture rather than their strong taste.

Are They Nutritious?

Water caltrops are primarily valued as a starchy food source.

Their edible kernels contain carbohydrates and also provide various micronutrients, although the exact nutritional composition depends on the species, growing conditions, preparation method, and serving size.

Like other plant foods, they can form part of a varied diet.

However, it's best not to believe exaggerated claims that portray water caltrops as a miracle food.

You may see social media posts claiming that unusual foods can “detox” the body, cure disease, or provide extraordinary health benefits.

There is no need for those claims.

The interesting part is already enough: this strange-looking aquatic fruit has been used as food in different cultures for generations.

Why Are They So Strange-Looking?

The horned shape is actually one of the most fascinating features of the plant.

The fruit develops underwater and eventually becomes hard and dark.

Its projections can make it look almost completely unlike an ordinary edible plant.

In fact, the unusual appearance has inspired names such as “bat nut” and “devil nut.”

Historically, the shape has also been compared with various weapons and animals.

This unusual structure isn't necessarily a sign that the fruit is poisonous.

Nature produces plenty of edible foods that look absolutely bizarre.

Think about dragon fruit, passion fruit, rambutan, durian, or even certain mushrooms.

Appearance alone doesn't tell you whether something is safe or unsafe to eat.

Correct identification does.

Could These Be Something Else?

This is where you should be cautious.

A photograph can help suggest an identification, but it isn't enough to guarantee that a wild or locally harvested plant is safe.

If these fruits came from a neighbor's garden, market, or known food source, ask:

What plant are they from?

Where were they harvested?

Were they grown specifically for eating?

How were they prepared traditionally?

Has the plant been positively identified?

If the person who gave them to you cannot answer those questions, it is better to pause before eating them.

Wild plants should never be identified solely from a viral social-media image.

How to Handle Them Safely

If they have been positively identified as an edible Trapa species and are from a safe food source, wash them thoroughly before preparation.

Discard any fruits that are moldy, rotten, badly damaged, or have an unusual odor.

Cook them thoroughly according to a reliable culinary source appropriate for the specific species.

After cooking, allow them to cool before attempting to open the shells.

Because the exterior can have sharp projections, handle them carefully.

And remember that children should not be allowed to play with the uncooked fruits because of their pointed surfaces.

Don't Confuse Unusual With Dangerous

The appearance of these fruits can easily trigger dramatic reactions online.

You might see captions claiming they are poisonous, parasitic, artificial, or even something completely unrelated to food.

Those claims should be treated cautiously.

The fruits in the image are consistent with water caltrops, but an image alone cannot establish the exact species or confirm that a particular batch is safe to consume.

The best approach is curiosity combined with caution.

Identify first. Prepare correctly. Eat second.

The Bottom Line

Those bizarre black fruits may be water caltrops, an aquatic fruit with a tough, horned shell and a starchy edible kernel inside.

They can be prepared by boiling, steaming, or roasting, followed by carefully cracking open the shell and removing the edible interior.

Their unusual appearance doesn't mean they're dangerous, but freshwater plants require appropriate handling.

Most importantly, don't eat an unknown wild or freshly harvested plant based only on a picture.

Ask the person who gave them to you where they came from and exactly what they are. If necessary, have the plant positively identified by a qualified local expert or agricultural extension service.

And if they really are edible water caltrops?

Congratulations—you've just discovered one of the weirdest-looking snacks that nature has to offer. 🌰🌿

Sometimes the strangest-looking foods really do have the most interesting stories.