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Spring Science – Cress Caterpillar

Growing cress is great for a fun, fast, educational gardening project. Cress is inexpensive, easy to grow and a fantastic way to teach children about germination and the conditions needed for healthy plants to grow.

We grew our cress caterpillar in an egg box and watered the seeds a little each day.

How to grow a cress caterpillar

  • cress seeds
  • an egg box, cut into segments
  • water
cress caterpillar made with eggboxes


Cress Caterpillar Instructions

  • Place some cress seeds in each segment of the egg box.
  • Place three segments on one plate or tray and three on another plate or tray.
  • Add water to all, and place one plate on a windowsill and one in the dark.
  • Water frequently.
cress caterpillar for a science experiment

The cress should grow within a few days. I gave my ‘in the dark seeds’ a little light to help them grow, which is why they are slightly green.

Why are the cress leaves green?

I was very surprised that the seeds grew so well without any soil. The water and nutrients stored in the seeds provided everything they needed to grow.

Green plants make sugar for growth through a process called photosynthesis.

Carbon dioxide + water  (and light ) ———> glucose and oxygen

Photosynthesis takes place in chloroplast cells, which contain a substance called chlorophyll, which makes plants green.

Sunlight is also needed to make chlorophyll, which is why cress seeds exposed to less sunlight are less green than those kept in the sun.

More plant and seed science for kids

Make an edible butterfly life cycle; use our free template to make it easy!

Edible Butterfly Life cycle. Fruit and vegetables used to make an edible butterfly life cycle.

Dissect a flower to learn about the structure and function of different parts of a flower.

labelled flower diagram using real flowers

Grow a bean in a jar! This is a great way to learn about germination.

Bean plant in a jar showing the roots after germination

Find out about leaf transpiration with Teach Beside Me.

Image of a cress caterpillar. Some cress seeds grown in the dark so the leaves are yellow rather than green

Last Updated on March 25, 2025 by Emma Vanstone

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