Dig Deeper: Grow your own cropmark

How to make..

Cress Cropmarks 


Cropmarks are made when there are ditches or walls buried underground.  This affects the way that the crops or grasses grow.  It affects the rate the crops grow and change colour and how tall and thick they become.   Sometimes these can be seen in aerial photographs of a field.  They can show the sites of houses or settlements. 

Ditches Crops above a ditch will be taller and grow close together.  This is because the ditch contains more water and nutritious organic matter than the surrounding soil.

Walls Crops above a wall will be shorter and sparser.  The buried wall gets in the way of the water getting to the plant roots.  The growing conditions are less good and the crops are smaller and less strong.

What you will need:

  • A seed tray or plastic food tray
  • Packet of cress seeds
  • Small stones
  • Compost/soil
  • Water spray
  • Cling film

What to do:

  • Build a wall down the middle of the tray.  This is your wall from the past!  Fill the tray with compost with a thinner layer over the wall. 
  • Scatter cress seeds over the whole tray and spray with water and cover the tray with cling film.  Place the tray in a warm place with a small amount of light. 
  • After 2 days your seeds will begin to sprout.  Uncover and leave the cress in good but not bright light.
  • Over the next week you will notice very little growth over the wall where the cress had little soil to grow in – you have made your own crop mark!

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