seaweeds | seagrasses
Seagrass or seaweed?
How to tell them apart?
updated Apr 2020

These two kinds of feathery/leafy lifeforms are often mistaken for one another. They are both green and leafy or feathery. Here's more on how to tell them apart.

Seagrasses have veins. Seaweeds do not have veins.
When you squish a small piece of seagrass, you don't get a mushy liquid as you do with seaweeds. When you squish a small piece of green seaweed, you get a mushy liquid.
Seagrasses have woody underground stems. Some green seaweeds may have underground structures that look like stems but these are not woody and do not have the same function as seagrass stems.
Seagrasses have real roots that absorb water and nutrients. They look like the roots of more familiar land plants. Some green seaweeds may have structures that look like roots but these merely grip the ground or surface and are not specialised for absorbing water and nutrients.
Seagrass leaves do not come in as wide variety of shapes as green seaweeds. They are either leaf-, fern-shaped or long and grass-like. Green seaweeds come in a wide variety of shapes. Some may be fern-shaped. Other shapes include bubbles, hair-like filaments, grapes, sheets, perforated ribbons, fleshy disks.
Seagrasses do not suddenly become extremely abundant. There may be variations in lushness of seagrass meadows, but this is not as sudden or large as with seaweeds. Some green seaweed species may be seasonally abundant, covering the shores in a thick layer and then disappearing several weeks later.
Seagrasses produce flowers and fruits, but for most species found in Singapore, these are tiny and they rarely bloom. Seaweeds do not produce flowers or fruits.

More comparisons

Mexican seaweed
Caulerpa mexicana

Delicate feathery green seaweed
Caulerpa sertularioides

Zipper green seaweed
Caulerpa cuppresoides

Bottlebrush green seaweed
Caulerpa webbiana

Scalpel green seaweed
Caulerpa scalpelliformis

Hairy green seaweed
Bryopsis sp.

Fluffy green seaweed
Caulerpa verticillata

how to tell apart different feathery green seaweeds
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