One quarter of children don't know butter comes from cows and even more don't know tomatoes grow on vines, a new survey has revealed.
There are fears that Australian kids are eating so much processed food that they have no idea about the origins of what they eat.
One quarter of students aged between five and 12 didn't realise butter and cheese came from cows, while one third didn't know tomatoes grew on vines, a survey shows.
The survey by the Stephanie Alexander Kitchen Garden Foundation and Medibank, released on Thursday, shows a disconnect between children and their diets.
Nearly half of the 1033 Australian parents surveyed said they were concerned their child was unable to make healthy food choices, and 60 per cent said they were concerned their child preferred processed food.
Chef, restaurateur and food writer Stephanie Alexander says instead of dining together at the table, children have been glued to their screens - making it easier for advertisers to influence their taste buds.
"It leaves children vulnerable to the power of the advertiser ... it's very hard for them to resist," she said.
"For many kids the positive modelling at home isn't there."
Healthy food choices were also important for combating obesity, with one in four Australian children obese or overweight, she said.
The chef, whose foundation helps schools set up gardens and kitchens, said healthy food habits taught at school had a positive impact on the family.
Stanmore Public School principal Fran Larkin has taken up the kitchen-garden program to teach children how to grow, prepare and cook meals at the Sydney school.
"I get parents telling me their children are eating things they wouldn't touch at home, like greens and other vegies," she said.