Is Bamboo a Grass or a Tree?

Short answer: Bamboo is a grass. It looks like a tree, because the stem grows tall and hard, but botanically bamboo belongs to the grass family along with wheat, rice and ordinary lawn grass. The difference lies in how the plant is built inside.

Why it is a grass

Grasses have hollow stems with nodes, grow from the base and have root networks that spread sideways. Bamboo has all three traits. A tree has solid wood, grows in thickness every year and forms annual rings, and bamboo does not.

No annual rings

A tree lays down a layer of wood each year, and those layers are what you see as rings in a trunk. A bamboo stem has no rings, because it does not thicken after the first year. It stays the same thickness for life.

Hollow inside

Cut a bamboo stem through and it is hollow with a dividing wall at every node. That construction is what makes it both light and strong, which is why bamboo works for scaffolding where the thickness would otherwise be too small.

How fast it grows

As a grass, bamboo grows by stretching segments that are already formed, which is why it goes so fast. A stem reaches its full height in a few months, where a tree takes decades to do the same.

What it means for the fibre

The cellulose in a grass and in a tree are alike enough that the same process works on both. That is why viscose can be made from bamboo and from wood, and the fibre ends up with the same basic properties.

What you notice in clothing

The difference between bamboo viscose and wood viscose is not noticeable in a garment. The process and the share in the blend decide how it feels. See bamboo underwear for women for what the material is used for most.

How hard it gets

Even though it is a grass, dried bamboo becomes harder than many kinds of wood. That is why it is used for floors and furniture, and the hardness comes from silica in the cell walls rather than from wood as in a tree.

For underwear

The hardness has nothing to do with clothing, because only the cellulose is used. See bamboo underwear for men, where the finished fabric is as soft as it is precisely because everything but the cellulose has been removed.

How many species there are

There are over 1,400 species of bamboo, from small plants half a metre high to stems over thirty metres tall. Only a few of them have stems thick enough to be used for textiles.

In bedding

The same applies to bedding, which is woven from the same fibre. See bamboo bedding if you want to feel how far the finished fabric actually ends up from the hard stem it started as. See also the honest guide to bamboo and the environment and bamboo and temperature regulation.