I believed that if I swallowed watermelon seeds that watermelons would grow in my stomach. I can't remember if that applied to any kind of seed.
A childhood belief about seeds

others believed things like this
- I use to believe (thanks to my Mom) that if I swallowed a watermelon seed a watermelon would grow in my belly.Anon
- I used to believe that if you ate a watermelon seed you would grow a watermelon tree in your stomach!!!— Eskimo
- I used to believe that if you swallowed watermelon seeds, they would dance around in your stomach at night.— jaalyn
- If you swallowed a watermelon seed it would grow in your belly— Rachelle
- I used to beleive that if you ate a black watermelon seed a tree would grow in your stomach— anonymous
- My Mom used to tell me if I swallowed an apple seed I would grow an apple tree inside my stomach!— Marg