How Roots Work

The hidden half of a plant

When you look at a plant, you see its stem, leaves and flowers. But there is a whole secret part you never see: the roots, growing down into the dark soil. Roots can spread surprisingly far — some are longer than the whole plant is tall! And they do some of the most important jobs of all.

Let's dig up the three big jobs of roots.

Job 1: Holding the plant steady

The first job of roots is to anchor the plant — to hold it firmly in the ground. Roots spread out through the soil and grip it tightly, like fingers holding on.

This is why a gust of wind does not knock most plants flat, and why it is so hard to pull a weed straight out without it snapping. A big tree's roots can spread out wider than its branches, holding tonnes of wood steady against the strongest storm. Roots also help hold the soil together so rain does not wash it away.

Job 2: Drinking water and minerals

The second job is to drink. Plants cannot survive without water, and it is the roots that take it in.

Roots soak up water from the soil, along with tiny amounts of minerals dissolved in that water — natural plant "nutrients" the plant needs to grow strong and green. The water then travels up through the stem to every leaf and flower. There, the plant uses water and sunlight to make its food through photosynthesis.

The secret of root hairs

How do roots drink so much? The answer is root hairs. Near the tip of every root grow thousands of tiny, almost invisible hairs. Each one is far too small to notice, but together they give the root an enormous surface to soak up water — like the difference between mopping a spill with one finger or with a whole sponge. The more surface, the more water the plant can drink.

Job 3: Storing food

The third job is storage. Many plants store extra food down in their roots, ready for when they need it.

In fact, you eat some of these food stores! A carrot, a beetroot and a radish are all swollen roots packed with the food the plant saved up. That stored food is why carrots taste sweet. To find out more about the foods that come from plants, read Fruits and Vegetables We Eat.

Two kinds of root system

Not all roots are shaped the same way.

• Taproot. One big main root grows straight down, with smaller roots branching off it. Carrots, dandelions and oak trees have taproots. A deep taproot can reach water far underground.
• Fibrous roots. Lots of thin roots spread out in a tangle, with no single main root. Grasses and many flowers have fibrous roots. These are great at holding the top layer of soil together.

Both kinds do the same three jobs — they just do them in different shapes.

How roots fit with the rest of the plant

Roots are one of the key parts of every plant, working together with the stem, leaves and flowers. To meet all of them, read The Parts of a Plant. The roots drink, the stem carries the water up, and the leaves use it to make food. Every part depends on the others.

Grow it and watch: see roots in action

You can actually watch roots grow, which is normally impossible because they are buried.

1. Take a clear glass jar and line the inside with a rolled-up piece of damp paper towel.
2. Slide a few bean seeds down between the paper and the glass, about halfway up.
3. Add a little water to the bottom so the paper stays damp, and put the jar somewhere warm and light.
4. Watch each day. Within a few days, a tiny root pushes out of each bean — and it always grows downward, even if you turn the bean upside down!

Look closely with a magnifier and you may spot the fuzzy root hairs. You are seeing the hidden half of a plant do its work.