I believed (thanks to my mum) that babies grew on "baby trees" and simply 'fell off' when they were ripe!!!
A childhood belief about reproduction

others believed things like this
- I believed that women who wanted babies ate a seed, which then grew into their baby. — World's Worst Scientist
- I thought a Monkey was just a baby Gorilla and when they grew up their Tails fell off!— Brainhead
- Hasn't everyone, at some point or another, believed that pickles grew on trees? I sure did.— Matt c.
- I used to think popcorn grew on trees until i was 13.— Davina
- i used to believe that spaggetti grew on trees!Anon
- I used to think that tea grew on trees already in mugs!Anon