This activity is a great way of helping your child to develop their hand-eye coordination and fine motor skills as they carefully cut and sponge paint the card before slotting the two parts together to create the finished item. It will also make your child think about different shapes and the structures that can be created from them. After they've made the cactus, let them have a go at making other things using the same technique, eg a wig-wam by slotting triangles of card together.
How to extend the magic
Talk about cactuses and how they are covered in very sharp spines which are very prickly. Explain that they grow in very hot, dry places such as deserts. Find some pictures of cactuses to show your child. Or, even better, if you have a cactus plant at home, let them take a look - but make sure you keep inquisitive little fingers at a safe distance!