Use this colorful poster in your classroom to teach the parts of a plant. Super Teacher Worksheets has many plant worksheets, including resources for parts of a plant, parts of a flower, and parts of a bean.
This is a wonderful flower matching game. For preschoolers, this would need to be a small group activity instead of an individual activity so that reading help could be given to the child. This is a great way to re-enforce the parts of a plant.