A plant's roots are like a person's mouth. This is how both humans and plants take in nutrients. By connecting the job of roots to something the children already understand, you provide the proper scaffolding for understanding the concept. Roots pull in nutrients (like food humans eat) from the soil to help the plant grow.
A plant's stem is like a person's legs. The stem holds the flower up and allows it to reach the sun and water it needs. The stem also carries the nutrients and water from the soil to the flower.
The flower is the part of the plant that makes more plants. The flower has pollen and tiny eggs. These parts change into a fruit. The fruit contains a seed. The seeds grow into new plants.
Create a flower from yarn, glue, and paper. Draw a line with the glue to represent the soil and more lines to represent roots. Cut brown yarn to fit the glue lines and place it on top of the glue. Next, draw glue lines to represent the stem and leaves. Cut green yarn to fit and place it on top of the glue. Finally, draw glue lines to represent a flower. Cut a different color yarn to fit and place it over the glue. Allow it to dry. Children can then label the flower parts with a crayon or marker.