Irish Moss vs. Bladderwrack: Meet the Seaweeds in the Bottle

Flip a bottle of Brazen Sea Moss Capsules around and you’ll see two seaweeds listed side by side: Irish moss and bladderwrack. They share a label, a coastline and a lot of history, but they’re not the same plant. Not even close, botanically speaking. One’s a red seaweed. One’s a brown one. Let’s make introductions.

First, a quick seaweed primer

“Seaweed” isn’t one kind of organism. It’s an everyday name for large marine algae, which are grouped by color into three broad families: red, brown and green. Those colors come from different pigments, and the groups are only distantly related. A red seaweed and a brown seaweed have about as much in common as a mushroom and a fern: both live in similar places, and that’s where the resemblance ends.

Irish moss belongs to the reds. Bladderwrack belongs to the browns. Neither, despite the name, is a moss.

Irish moss: the red one

What it is

Irish moss is Chondrus crispus, a small, bushy red seaweed with flat, forking fronds that fan out like a tiny, rubbery shrub. Depending on how much sun it gets, it can look deep purple-red, reddish-brown or even greenish-gold. When it’s harvested and dried, it often bleaches to a pale cream color.

Where it grows

It lives on rocky shores on both sides of the North Atlantic, from the coasts of Ireland, Britain and Northern Europe to the Atlantic coast of North America, including the Canadian Maritimes and New England. You’ll find it low on the shore, around and below the low-tide line, clinging to rocks.

A kitchen history

In Ireland, Irish moss is also called carrageen, and it has been a pantry staple on the coast for generations. Simmered in milk, it releases a natural gel that sets as it cools, which is how cooks made a soft, wobbly, blancmange-style pudding, often flavored with vanilla, lemon or a little sugar. It was also traditionally simmered into warm drinks at home.

That gelling talent has a modern legacy. Carrageenan, the thickener you’ll see on ingredient lists for things like plant milks and ice cream, takes its name from carrageen, and Irish moss was its original source. Today carrageenan is extracted from several red seaweeds, but the name still points back to the Irish coast.

The Caribbean connection

Across the Atlantic, “Irish moss” or “sea moss” is the name of a beloved drink in Jamaica and throughout the Caribbean: seaweed soaked, boiled into a gel and blended with milk and warm spices like cinnamon, nutmeg and vanilla. Here’s a fun wrinkle: the seaweed used in Caribbean sea moss is often a different red seaweed from warmer waters, such as species of Gracilaria or Eucheuma. “Sea moss” is a name that travels loosely. That’s one reason it’s worth checking a label for the botanical name when you want to know exactly which plant you’re getting.

Bladderwrack: the brown one

What it is

Bladderwrack is Fucus vesiculosus, a brown seaweed with flat, olive-to-brown fronds that fork as they grow, each with a distinct central rib. Its signature feature is right there in the name: small, rounded, air-filled bladders, usually in pairs along the frond. Those bladders act like little floats, lifting the fronds toward the light when the tide comes in. Pop one (everyone who grew up by the sea has) and you’ll get a satisfying little snap.

Where it grows

Bladderwrack is one of the most familiar seaweeds of the North Atlantic, found on rocky coasts from Northern Europe, including the North Sea and the Baltic, to the Atlantic shores of North America. It grows higher up the shore than Irish moss, in the middle of the intertidal zone, forming thick, slippery carpets over rocks that are exposed at low tide. If you’ve ever lost your footing on a seaside rock, bladderwrack may have been involved.

A working-seaweed history

Bladderwrack and its fellow wracks have long been useful on the coast. Coastal farmers in places like Ireland and Scotland gathered seaweed from the shore and spread it on fields as fertilizer. Seaweeds, wracks included, were also burned to make “kelp,” an ash that was an important industrial raw material for making soap and glass in the 18th and early 19th centuries. And in 1811, the French chemist Bernard Courtois discovered iodine while working with seaweed ash, a nice reminder of how much chemistry the humble shore has contributed.

Red vs. brown at a glance

• Irish moss (Chondrus crispus): red seaweed; bushy, flat, forking fronds; grows low on the shore; famous in Irish kitchens and the namesake of carrageenan.
• Bladderwrack (Fucus vesiculosus): brown seaweed; ribbed fronds with paired air bladders; grows mid-shore; long used on coastal farms and in the old kelp-ash trade.

Their bottle-mates

The two seaweeds aren’t alone in the capsule. Burdock root comes from Arctium lappa, a tall plant whose prickly seed heads are famous for sticking to socks and dog fur. Its long root is eaten as a vegetable in Japan, where it’s called gobō and often shredded into stir-fries. BioPerine® is a branded extract of black pepper fruit, the same peppercorns in your grinder, and a common addition to botanical formulas.

Where Brazen fits

Our Sea Moss Capsules put all four on the label, with every amount printed: Irish moss 500 mg, bladderwrack 500 mg, burdock root 400 mg and BioPerine® 5 mg per two-capsule serving. Red seaweed, brown seaweed, a root and a peppercorn, no guesswork about who’s in the bottle.

This article is for general information and isn’t medical advice. Talk to your healthcare professional before starting any supplement.