Watercress vs Arugula vs Wolffia: Two Peppery Classics vs One Tiny Protein Plant

Watercress vs arugula is a debate that pops up every time someone stands in the produce aisle holding watercress in one hand and arugula in the other, wondering which leafy green is worth it. Fair question. But I want to throw a third contender into the ring. One you've probably never eaten.

Wolffia.

Quick disclosure before we go any further: I'm Robbie, the founder of Wolfa, and I'm building a brand around Wolffia. So yes, I'm biased. I'll show you the research, give watercress and arugula full credit (they deserve it), and you decide. Deal? Deal.

Note: If leafy greens give you the vitamins but not the protein or B12, Wolffia fills that gap without changing how you eat. It's a single whole-plant ingredient from one traceable farm in Thailand: non-GMO, pesticide-free, no added sugar, and no proprietary blends. Join the Wolfa waitlist at mywolfa.com and you'll be first in line when we launch.

Meet the Contenders

All three are green, all three are rich in nutrients, and all three are low risk, high reward food. (Low risk, as long as you check the safety note below.) That's roughly where the similarities end. They differ in flavor, form, protein quality, and how much effort it takes to eat them. Underdog first.

Wolffia: The World's Smallest Flowering Plant

Wolffia globosa is a tiny aquatic plant from the duckweed family (Lemnaceae). No roots, no stems, no real leaves. Just little green spheres, about half a millimeter across, floating on fresh water. It's been eaten as a vegetable in Thailand, Laos, and Burma for a long time, which is where I first came across it. My brain short-circuited a little when I learned what was packed into something smaller than a sesame seed.

Here's the short version of Wolffia nutrition. In clinical research on a cultivated strain of Wolffia globosa, the plant came in at more than 45% protein by dry weight, with all nine essential amino acids, a protein quality score (PDCAAS) of 89%, and some omega-3 fats. It also contains bioactive vitamin B12, which is almost unheard of for a leafy green or any plant. And since it's so small, there's nothing to chop, de-stem, or wash.

Save Your Spot for Wolfa

I'm finalizing our Wolffia with one of the top farms in Thailand, and waitlist members get first access before anyone else. One spoonful, real plant nutrition, done. Join the waitlist at mywolfa.com

Watercress: The Peppery Water Green

Watercress (Nasturtium officinale) is a semi-aquatic perennial in the Brassicaceae family, the same crew as cabbage, broccoli, and mustard greens. Watercress has small, rounded, vibrant leaves, crisp stems, and a fresh, peppery flavor. Think of watercress as broccoli's spicier, leafier cousin.

Wild watercress grows in cool, flowing water, and today watercress is commercially cultivated in shallow spring-fed beds. That's why you can usually find watercress year round (well, mostly year round), bundled near the herbs or sold "living" with roots attached. Fresh watercress is one of those vegetables that looks fancy but is honestly easy to find.

Arugula: The Bold Salad Staple

Arugula (Eruca vesicaria), also part of the Brassicaceae family, is a leafy annual with long, lobed leaves and a punchy bite. It's the green you see piled on pizza, in salads, or tossed into pasta dishes at every Italian spot you've ever been to.

(Side note: in the UK, arugula is called "rocket." Way cooler name. Arugula sounds like a sneeze.)

Is Arugula the Same as Watercress?

Nope. Arugula and watercress are cousins, not twins. Unlike spinach, both belong to the Brassicaceae family of cruciferous vegetables, and both bring a peppery flavor. That's why people mix them up, and why recipes often swap one for the other.

But they have different personalities, and you can taste it. Watercress is crisp and bright with a clean heat. Arugula is bolder, with a slightly bitter, nutty finish. Wolffia, for the record, isn't closely related to watercress or arugula. Different family, totally different body plan, totally different nutrition story.

Watercress vs Arugula vs Wolffia: The Nutrition Numbers

Okay, nutrition nerd time. Watercress and arugula calories and other numbers are per 100g raw. Wolffia figures come from published clinical research on Wolffia globosa.

Watercress and arugula are both featherweights on calories and carbs, with barely any fats and very little sugar. Both have less than a gram of fats per 100g. Great for volume. Great for salads.

But as protein sources, watercress and arugula are about what you'd expect from leafy vegetables: a couple of grams per 100g. Wolffia plays a different game entirely.

Where Wolffia Pulls Ahead

Watercress is a leafy green legend (more on that soon). But Wolffia does a few things none of the leafy vegetables on your grocery shelf can match.

Complete Protein, Not Just "Some" Protein

Many plant proteins come up short somewhere. Grains tend to run low on lysine, legumes tend to run low on methionine, and leafy vegetables like spinach and watercress just don't carry much protein in the first place.

Wolffia is different.

Researchers have reported that its essential amino acids show up in a ratio comparable to egg protein. In a randomized trial with 36 men, the amino acids from Wolffia were absorbed into the bloodstream, and the researchers concluded it may be a high-quality alternative to animal protein. That's not "a little protein for a green." That's protein that counts. It's why wolffia is a top-ranked vegan protein supplement.

Vitamin B12 From a Plant (Yes, Really)

This is the one that genuinely got me.

B12 is the classic gap in plant-based eating. Watercress has none. Arugula has none. Spinach and kale? None.

Wolffia globosa contains bioactive vitamin B12, and research published in Nutrients found it's well absorbed in humans. In that same protein trial, blood B12 rose more after eating Wolffia than after eating cheese or peas. One cup of the Wolffia shake used in clinical research (about 20g of dry matter) covered roughly a fifth of daily B12 needs.

It's honestly the best plant-based B12 supplement.

Iron That Your Body Can Actually Use

Plant iron is famously hard to absorb, so researchers tested it. In the DIRECT-PLUS trial, after six months, people on a low-meat green Mediterranean diet that included a daily Wolffia shake saw a modest rise in hemoglobin and serum iron. In anemic rats, Wolffia iron reversed anemia about as well as a standard iron supplement.

What the Clinical Trials Found

Wolffia has its own body of human trials, including the large DIRECT-PLUS study (NCT03020186).

• Blood sugar: In a crossover trial, people swapped dinner for either a Wolffia shake or a yogurt shake with matching carbs, protein, and calories. The Wolffia shake was associated with a lower post-meal blood sugar peak and slightly lower fasting blood sugar the next morning.
• Liver fat: In DIRECT-PLUS, the green Mediterranean group (Wolffia shake, green tea, walnuts, less red meat) lost almost double the liver fat of the regular Mediterranean group.
• Polyphenols: Wolffia is rich in polyphenols, with 198 different phenolic compounds detected.

Those were whole diet patterns, not a magic single food. Still, pretty exciting.

And then there's the planet. Wolffia grows on water, needs no soil, and is one of the fastest-growing plants on Earth, doubling in as little as a day.

Want to try Wolffia without hunting through an Asian market? I'm working with a single, traceable farm in Thailand on a clean, non-GMO, pesticide-free Wolffia with no added sugar and no proprietary blends. Join the Wolfa waitlist and you'll be first in line when it launches.

Which Is Healthier, Watercress or Arugula?

Back to the classic watercress vs arugula matchup, minus the tiny green newcomer. On pure nutrient density, watercress wins. Watercress packs more vitamin C and vitamin K per bite and has fewer calories. It also famously topped a nutrient density ranking published by the Centers for Disease Control and Prevention (CDC).

But arugula isn't a pushover in the nutrition department. Per serving, arugula provides more protein, fiber, and folate than watercress, plus a bit more calcium and potassium. Arugula is also rich in dietary nitrates, which can improve blood flow. So the honest answer: watercress is the more nutrient-dense of the two, but arugula has its own wins.

Eating both watercress and arugula is a perfectly reasonable move. Rotate them through your salads.

Is Watercress the Healthiest Vegetable in the World?

By one well-known measure, yes.

In 2014, a study in the CDC's journal Preventing Chronic Disease ranked "powerhouse" fruit and vegetables by how many key nutrients they deliver per 100 calories, focusing on nutrients tied to lower chronic disease risk. Watercress was the only one to score a perfect 100. That's why watercress gets called the healthiest vegetable on lists all over the internet.

For context, Chinese cabbage scored about 92, spinach about 86, and kale scored 49.07. Plenty of other vegetables and fruit made the list too, but none of those vegetables matched watercress. So which is healthier, kale or watercress? On that scale, watercress more than doubles kale. (Anyone else feel slightly betrayed after years of being told kale, not watercress, was king?)

Now, is watercress the healthiest leafy green you can eat? On nutrients per 100 calories, watercress sits at the top. But that study didn't include Wolffia, and it scored nutrients per calorie, not protein quality. If your goal is complete protein and B12 from plants, the "healthiest vegetable" answer changes. Context matters for your health.

Health Benefits of Watercress and Arugula

Watercress and arugula are both vegetables packed with antioxidants. Here are the potential health benefits of watercress worth knowing:

• High in vitamins A, C, and K, which support overall health. Vitamin C also supports immune function.
• Contains glucosinolates, compounds that may have cancer-fighting properties.
• Consuming watercress may lower LDL cholesterol levels in overweight individuals.
• A source of calcium for bone health, plus potassium, manganese, and other minerals.
• At 11 calories per 100g, watercress fits easily into a weight loss diet.

The health benefits of arugula overlap a lot with the health benefits of watercress. Arugula contains vitamins A, C, and K and is rich in nitrates that can improve blood flow. It's also low in calories, which makes it a smart pick for weight loss.

A quick safety note. Vitamin K plays a key role in blood clotting. If you take blood-thinning medicine, suddenly eating a lot more of any leafy green can affect how that medication works. Patients on blood thinners, older people, and anyone managing a health condition should check with their doctor before making big changes to their diet, to lower the risk of interactions. That includes adding Wolffia or any new food. Other patients on long-term medication should do the same.

How They Taste and How to Use Them

Here's where watercress and arugula really shine. They bring real, peppery, wake-up-your-mouth flavor.

The watercress taste is peppery and sharp with a crisp texture. Raw watercress is lovely in salads and sandwiches. Cooked, watercress blends into a vibrant green watercress soup or gets tossed into stir fries at the last second. Arugula has a bold, pungent flavor with a slightly bitter finish, and it's at home on pizza, folded into pasta dishes, or piled into grain bowls. You can substitute watercress with arugula in most recipes, and vice versa. Pasta dishes, egg dishes, and grain recipes all handle the swap well.

Compared to watercress, Wolffia plays a totally different role. It's not trying to be the star of your salads. It's the nutrient upgrade you stir into food you're already eating: yogurt, green smoothie recipes, soups, or grain dishes. Treat it like a seasoning for your food. No chopping. No washing. No soggy leftovers wilting in the back of the fridge.

Watercress storage tip: keep fresh watercress stems-down in a glass of water in the fridge, like herbs. Arugula likes to be dry and wrapped in a paper towel. Watercress and arugula are best eaten within a few days, while still vibrant and green.

Is It Healthier to Eat Watercress Raw or Cooked?

Both work. Raw watercress keeps more of its vitamin C, which breaks down with heat, plus that crisp texture and peppery bite. Like spinach, cooked watercress wilts down a lot and its flavor mellows. That makes it a delicious way to sneak more greens into soups, stir fries, and pasta. You'll lose some vitamin C, but you'll probably eat more (and watercress calories stay tiny either way).

My lazy rule: raw watercress in salads and sandwiches, cooked watercress to use up a big bunch fast. To enjoy watercress with zero effort, toss a handful into stir fries right before they come off the heat. A delicious treat.

What Is the Closest Vegetable to Watercress?

Arugula is the closest watercress swap for most people: same family, same peppery flavor, sold at basically every grocery store. But if you want to explore beyond arugula, a few other vegetables do the job:

• Radish sprouts are the closest thing to watercress in flavor. Radish sprouts bring that same peppery kick and crunch as watercress, and radish sprouts shine on sandwiches and salads. If you love raw watercress, try radish sprouts.
• Mustard greens have a stronger, spicier heat than watercress. Young leaves work raw; mature ones are better cooked.
• Dandelion greens lean more bitter than watercress. Dandelion greens are great sautéed with garlic, or chopped small into salads with a sweet dressing. Explore dandelion greens if you like a bitter edge. Baby spinach works in a pinch too, minus the heat.

And if it's arugula you're out of, I put together a full rundown of the best alternatives to arugula that covers a bunch of these peppery veggies in more detail. None of these vegetables come close to Wolffia on protein, though. They're flavor substitutes. Wolffia is a nutrition upgrade.

So, Which One Should You Pick?

• Pick Wolffia if you want complete protein, naturally occurring B12, and iron in a whole food that takes literally zero prep. It's the one that fits a busy (or lazy) life.
• Pick watercress if you want the most nutrient-dense leafy green per calorie (watercress is the CDC's top scorer), loaded with vitamin C and glucosinolates, for salads, sandwiches, and soups.
• Pick arugula if you want a bold, sharp bite for a salad, pizza, or pasta, plus more fiber and folate for very few calories.

Honestly? You don't have to choose. Watercress vs arugula was never really a fight. Use both for flavor, and let Wolffia handle the protein and B12 that leafy vegetables can't. If that sounds like your kind of food, join the Wolfa waitlist. We're just getting started.