Have a tasting party with the children. Use all different fruits and vegetables to taste. For older kids you could even graph their favorite.
I set up a farmer’s market in dramatic play. It had fake fruit and vegetables, fake money, gourds, fake flowers for sale, empty egg cartons…etc. Also, chalkboards listing fresh vegetables, hours open, etc…I leave chalk available to write on boards. To introduce the center I read Ox Cart Man and then we discuss what a farmer is and what a farmer’s market is.
Take a field trip to a farmers market. Take enough parents that children are allowed to browse at their leisure to find the fruits and vegetables you have talked about.