Year 3 science · Key Stage 2 · Plants

Year 3 plants: parts of a plant, water and the life cycle

In Year 3, children learn that every part of a flowering plant has a job. They find out what plants need to live and grow, watch how water travels up a stem, and learn how flowers help a plant to make new plants through pollination, seed formation and seed dispersal. It builds on Year 2 work on how seeds and bulbs grow.

Parts of plants and life cycles, explained

The central idea is that structure and function go together: every part of a plant has a job. The roots hold the plant in the soil and take in water and nutrients from it. The stem (or trunk, in a tree) holds the plant up, carries water and nutrients to the rest of the plant, and lifts the leaves towards the light. The leaves are where the plant makes its food. Children don’t need to know how, only that plants make their own food and animals can’t. The flowers are for reproduction, which means making seeds that grow into new plants.

Children then explore what plants need for life and growth: air, light, water, nutrients from the soil, and room to grow. They also find out that the amounts vary from plant to plant. A cactus needs very little water, a plant from a woodland floor may grow better in shade, and a plant crowded into a small pot may grow weak and thin. A typical class investigation compares plants given different amounts of light or water. This links well to the working scientifically skills of fair testing.

Water transport is explored practically. A white carnation, or a stick of celery with its leaves, is stood in water with food colouring and left for a day or more. The colour appears in the petals and leaves, and cutting the stem across shows coloured dots where it has travelled up. This shows that the stem carries water to the parts of the plant that need it. An adult should do any cutting.

The last strand is the life cycle. Before a flower can make seeds, pollen has to be carried to the part of a flower that makes seeds, usually on another flower of the same kind. This is called pollination, and it is often done by insects that visit for nectar, or by the wind. After pollination, seeds form, often inside a fruit. They then need to be moved away from the parent plant, called seed dispersal, so they have room to grow. Seeds can be carried by the wind (dandelions and sycamore seeds), by animals (sticky burrs or fruit that is eaten and the seeds dropped later), by water, or flung out when a seed pod dries and bursts open. Children can link the shape of a fruit to the way its seeds travel. The cycle then begins again when a seed lands somewhere suitable and germinates, which means it starts to grow.

Words your child will hear

Root: The part of a plant, usually underground, that holds it in place and takes in water and nutrients.
Stem: The part that holds a plant up and carries water and nutrients around it. In a tree it is the trunk.
Nutrients: Substances in the soil that a plant needs to grow healthily.
Pollination: Pollen being carried to the part of a flower that makes seeds, usually on another flower of the same kind, often by insects or the wind.
Seed dispersal: Seeds being carried away from the parent plant, for example by wind, water or animals.
Life cycle: The series of stages in a living thing’s life, from seed to adult plant and back to seed.
Function: The job that a part does.

What the National Curriculum says

In Year 3, pupils should be taught to:

Identify and describe the functions of different parts of flowering plants: roots, stem/trunk, leaves and flowers
Explore the requirements of plants for life and growth (air, light, water, nutrients from soil, and room to grow) and how they vary from plant to plant
Investigate the way in which water is transported within plants
Explore the part that flowers play in the life cycle of flowering plants, including pollination, seed formation and seed dispersal

Objectives from the National Curriculum in England, © Crown copyright, used under the Open Government Licence v3.0.

Try it: following the water up a stem

How can we show that water travels up the stem of a plant?

Make a prediction. “I think the water will go up the stem because the flower needs it, and the stem is the only part that joins the flower to the roots.”
Set up the test. Fill a glass about halfway with water and stir in a good amount of food colouring. Stand a white carnation or a stick of celery with its leaves in the water. Use a second one in plain water for comparison.
Observe at intervals, for example after an hour, the next morning and the day after. Draw what you see and label the parts. The petal edges or celery leaves gradually take on the colour.
Look inside the stem. An adult cuts across the celery stalk or carnation stem. The cut face shows small coloured dots, which are the tiny tubes that carry the water.
Explain the observation using the science words: water is taken up by the stem and carried to the leaves and flowers.

The coloured water moved up the stem and into the petals or leaves, so the stem carries water from the roots to the rest of the plant. The plant in plain water stayed white, which shows that the colour came from the water we added.

Common mistakes and how to help

Thinking plants get their food from the soil

Plants are in soil and we feed them “plant food”, so children assume the soil is their dinner.

What helps: Explain that roots take in water and nutrients, which help the plant stay healthy, but plants make their own food in their leaves using light. Animals, by contrast, have to eat.

Believing all plants need the same amount of water and light

A bean seedling is the most common classroom plant, so children generalise from it.

What helps: Compare very different plants: a cactus, a water lily and a woodland fern. Ask where each grows naturally and what it would find easy or hard.

Thinking flowers are just decoration

Flowers are what we notice and enjoy, so children may not see that they have a job.

What helps: Look closely at a flower, then at the fruit that follows it. Ask “What was the flower for?” and follow the bee from flower to flower.

Mixing up pollination and seed dispersal

Both involve something being carried, by animals or the wind, and the words are new.

What helps: Pollination happens first and happens to the flower: pollen is carried to another flower. Seed dispersal happens later: the finished seeds are carried away from the plant.

How to help at home

Colour a celery stick. Stand a celery stick with leaves in a glass of water with food colouring and check it each day. An adult can slice across the stalk at the end to see the coloured dots.
Grow cress or beans. Grow several pots with the same seeds, giving some more light, some less and one none. Keep everything else the same, such as the amount of water and the type of pot. Measure the growth in centimetres every few days and talk about what each plant needed.
Dissect a flower. Use a flower from the garden (ask first) or one from a shop-bought bunch, and pull it apart carefully. Avoid poisonous plants such as foxgloves, daffodils and lily of the valley. Look for petals, the sticky or fuzzy parts in the middle and any pollen. Don’t eat any part of it, and wash your hands afterwards.
Seed detectives. Collect seeds on a walk or from fruit, such as an apple, a sycamore wing or a dandelion clock. Ask how each might travel and test by dropping or blowing them.

Builds on

Year 2: How seeds and bulbs grow

Everything in Year 3 science

Updated 20 October 2026.