Extreme Drawing

Growing cress with kids: seeds that sprout in days

Kitchen science experiment

Seeds that wake up when they get a drink

Cress seeds sprout in a day or two, as long as they stay damp. Water switches them on, and once they have started, drying out can kill them. In about a week you have a small green lawn you can snip and eat.

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  • Ages 4+
  • 10 minutes to sow
  • Ready in about a week
Painted illustration of the painter spraying water on cress sprouting in a heart shape on damp kitchen paper, with a seed packet and seeds.

Quick facts

Age
4 to 10
Time
10 minutes to sow, 5 to 7 days to grow
Mess
Low
Adult needed
A little help, and for the scissors
You need
Cress seeds, kitchen paper or cotton wool, a saucer (very cheap)
On screen / for real
Both

In Extreme Drawing

Two ways to sow on screen:

  • Chia seeds or Flax seeds from the sieve on the Kitchen tab. Sprinkle them into water or onto wet paper: they drink, swell into their gel and then come up as cress, after about a day kept damp.

  • Seeds on the Garden tab (in the full toolbox), with Cress, Grass seed and Moss. Cress is the quickest to come up.

Seeds only count time while they're damp: on wet paper, in a puddle, in mud or in gel. On dry paper they just wait. The game's clock runs about an hour for every real minute, and Wait 3 days on the Time tab jumps ahead so you can see the lawn.

Dry spells matter. While you play, a seed that started to drink and then dries out waits for the next watering. But over a time skip, a seed left dry for a day dies, and sprouts that dry out go yellow and flop (water them soon and they perk up again). Heat over 60 °C or the oven kills seeds, and ground flax doesn't sprout at all.

Try this: sow half your seeds on wet paper and half on dry, then tap Wait 3 days.

Play in your browser
Painted illustration of the painter sniffing a lemon behind a counter with ketchup, mustard, honey, an egg, oil, butter, flour, salt, sprinkles and a rolling pin.

Do it for real: a cress head

You need

  • Cress seeds (or mustard and cress, or chia seeds), sold for eating or sprouting

  • Kitchen paper, cotton wool or a clean sponge

  • A saucer, a clean half eggshell or a yoghurt pot

  • Water, and a spray bottle if you have one

  • Felt-tips to draw a face on the eggshell or pot

  • Scissors (for a grown-up)

  1. Make a damp bed

    Fold kitchen paper into the saucer (or press cotton wool into the eggshell). Wet it until it is soaked, then tip away the extra water.

  2. Draw a face

    For a cress head, draw a face on the eggshell or pot. The cress will be its hair.

  3. Sprinkle the seeds

    Scatter the seeds thinly over the damp bed. Don't bury them: cress sprouts on top.

  4. Set up a dry one

    Put a few seeds on dry kitchen paper in a second saucer. This is your test: will they grow?

  5. Keep it damp

    Put both on a light windowsill. Spray or dribble a little water on the damp one once or twice a day: damp, never dry, never a puddle.

  6. Look every day

    After a day or two you see tiny white roots with fuzzy root hairs, then pale stalks, then two green seed leaves.

  7. Snip and eat

    After about a week, when the cress is a few centimetres tall, a grown-up snips it with scissors. Try it in an egg sandwich.

Painted illustration of the painter spraying water on cress sprouting in a heart shape on damp kitchen paper, with a seed packet and seeds.

Why it works

For kids: a seed is a tiny baby plant with a packed lunch. When water soaks in, the seed swells and the baby plant wakes up. It pushes out a root to drink and a shoot to reach the light, and uses its lunch until its green leaves can make food from sunlight.

For grown-ups: germination starts with imbibition: the dry seed takes up water, swells and switches its metabolism back on, using the food stored in the seed. It needs water, oxygen and a suitable temperature. Light isn't needed to sprout, but it is needed to grow green leaves: cress kept in the dark grows tall, thin and pale (etiolation). Once a seed has started to germinate it loses much of its tolerance to drying, which is why a dry spell after sowing can kill it. Chia and flax seed coats make mucilage, the gel you see when they're wet.

The game models the water and the heat, not the light. So the dark-cupboard test is one to do for real.

Try next: predict, then test

Light or dark?

Grow one saucer on the windowsill and one in a dark cupboard. Which grows taller? Which is greener?

Warm or cold?

Put one saucer in the fridge and one in the kitchen. Do both sprout?

Skip a day

What happens if you forget to water for a day, once the roots are out? Try it on screen with Wait 3 days first.

Which seed is fastest?

Cress, chia or flax: sow them side by side and count the days until the first roots show.

For teachers

Growing cress fits KS1 Year 2 "plants" (seeds need water and a suitable temperature to grow) and NGSS 2-LS2-1 (plants need water and light). Use the app on the whiteboard for the water half of the test, wet against dry paper with Wait 3 days, and real saucers for light against dark.

Ideas for teachers

Questions about growing cress

How long does cress take to grow?

Roots show in one or two days and green leaves in three or four. It is ready to snip in about a week.

Does cress need light to grow?

It sprouts without light, but it needs light to turn green. In a dark cupboard it grows long, thin and yellowish.

Can you grow cress on cotton wool?

Yes. Cotton wool, kitchen paper, a sponge or soil all work, as long as they stay damp.

Why did my cress stop growing?

Most often it dried out. Seeds that have started to sprout and then dry out for a day usually don't recover, so keep the bed damp every day.

Is the white fuzz on cress roots mould?

In the first days it is usually root hairs, which help the root drink. Mould looks like fluffy cobweb on the seeds themselves and smells musty.

More things that grow and change

Sow it now, skip three days

Sprinkle chia seeds into a puddle on screen and watch them come up. Then start a real saucer on the windowsill.

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