When you are happy with your greenhouse, it is time to add the plants!

Remove the lid and place a thin layer of cotton wool in the bottom of the tray, so that all of the tray is covered. Sprinkle the mustard and cress seeds onto the cotton wool, and add enough water to dampen the cotton wool (but not to flood it).

Put the lid back on the greenhouse and put it in a warm place. Add water every day to keep the cotton wool moist. After a few days your mustard and cress plants will appear!