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For kids · ages 5–12

Sunflower experiments for home

Four experiments you can do at the kitchen table, with things you already have at home. All safe — though it's better to have a grown-up help with the cutting. Grab a pencil to write down your measurements!

Good to know: for each experiment you'll find what you need, how it works (step by step) and what you learn. Some take a few minutes, others a few days. Write down what you see each time — that's what real scientists do too!

Experiment 1 · Make a flower change colour

Flowers and stems drink up water through tiny little tubes, a bit like a straw. That is called capillary action. With coloured water you can make it visible.

What do you need?

  • A white flower (for example a white tulip or daisy) or a stick of celery with leaves
  • A glass or small vase of water
  • Strong colouring: blue or red food colouring (from baking)
  • Scissors and a grown-up to help with the cutting

Steps

  1. Put water in the glass and stir in a good splash of food colouring, until the water is really dark.
  2. With help, cut the bottom of the stem off at an angle, so it is fresh.
  3. Stand the flower or celery in the coloured water.
  4. Wait. Look after 1 hour, after a few hours and the next morning.
  5. With the celery you may cut it through after a day: can you see the coloured tubes?

What do you learn? The colour slowly creeps up through the tubes and colours the leaves or petals. That way you can see how a plant gets water from its roots up to the top — with no pump at all. A real sunflower does exactly the same, only much bigger.

Experiment 2 · Sprout seeds in a jar

You don't need a garden to watch a seed sprout. In a glass jar you can see everything happen, including the roots.

What do you need?

  • A clean glass jar (for example a jam jar)
  • Some kitchen paper or cotton wool
  • 2 or 3 sunflower seeds (unroasted, unsalted — the ones for the birds are fine)
  • A little water

Steps

  1. Stuff the kitchen paper loosely into the jar, against the side.
  2. Tuck the seeds between the glass and the paper, so you can see them through the glass.
  3. Dampen the paper with a little water. It should be moist, not standing in water.
  4. Put the jar in a light, warm spot, for example on the windowsill.
  5. Keep the paper a little damp every day and watch what happens.

What do you learn? After a few days the seed bursts open. First a little root comes down, then a little stem goes up. You can see that a root always grows downwards and the stem upwards — even if the seed is lying crooked! Want to sow for real in the garden afterwards? Then have a look at the sowing calendar.

Experiment 3 · Measure whether the flower follows the sun

Young sunflowers turn their heads with the sun during the day, from east to west. That is called heliotropism. Can you measure it?

What do you need?

  • A young sunflower in a pot or in the garden (not yet finished flowering)
  • A compass (or the compass app on a phone, with a grown-up to help)
  • Your grow diary or a sheet of paper

Steps

  1. Early in the morning, look which way the flower head is pointing. Write it down: east, south or west?
  2. Look again around midday. Which way now?
  3. Look once more at the end of the afternoon and write it down.
  4. Do this for a few days in a row. Draw an arrow for the direction each time.

What do you learn? In a young plant you can see the head slowly turn with the sun. Once the flower is grown up, that stops and the head stays facing east for good. Why that is handy for the bees, you can read on heliotropism.

Experiment 4 · Count the Fibonacci spirals

You do this experiment with a real faded sunflower, or with a big photo of the middle.

What do you need?

  • A faded sunflower head with seeds (or a clear photo)
  • Two colours of felt-tip or pencil
  • A little patience

Steps

  1. Choose one spiral that turns outwards from the middle and trace it with your first colour.
  2. Count how many of those spirals there are in total that turn the same way.
  3. Now take your second colour and do the same with the spirals that turn the other way.
  4. Write down both numbers. Do they match the sequence 21, 34, 55, 89?

What do you learn? The two numbers you count almost always sit next to each other in the Fibonacci sequence (1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89...). You often find 34 and 55. The plant uses this clever pattern so it can fit in as many seeds as possible without them fighting over space. More maths from nature can be found on Fibonacci.

Take care

Always ask a grown-up to help with the scissors or the knife. Don't eat the food colouring and don't drink the coloured water. Wash your hands after working with soil and plants.

For teachers and parents

These experiments use only safe, everyday materials and are suitable across the whole primary range (with supervision for the cutting). They link up with inquiry-based learning: ask a question, predict, observe and record. Experiment 1 shows capillary action and transport in plants, experiment 2 germination and geotropism, experiment 3 heliotropism, and experiment 4 patterns and number sequences. Have pupils write down a hypothesis each time before they observe. Background with sources can be found on heliotropism and Fibonacci.

Tip: let a child keep their own "research notebook" with the date, a prediction and a drawing of what happened. That turns a fun experiment into a real mini-investigation.

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