When I was little I used to believe that when you watered the flowers, you had to pour the water on the flower part of the plant. That was because where the flower was, I thought that that was trhe "mouth" where it takes in water. I believed this until age 7 when I learned that plants get their water by soaking it up from the roots, not the flower!
A childhood belief about plants

others believed things like this
- When I was little I thought that a "wallflower" was a kind of flower that grew on walls.— A. Nonny-Muss
- i used to believe that a perrenial was a particular flower's name— Ducki
- I thought that hydrogen was pure water (since I knew hydro- meant water) and H2O was impure some how— Hexetic
- When I was a kid I took two showers becaue I thought my hair was a plant and needed the water to grow— Tim
- I used to believe that if i splashed water on the wall during a bath, the water would turn into spiders— justin
- that bathroom tap water was recycled "potty" water from the toliet. — livingdeadgirl