I had just learned a few minutes ago that a nightshade was a plant. I always thought it was a lampshade that was especially bright so you could use it at night.
A childhood belief about plants

others believed things like this
- When I was a kid, I used to believe a nuclear plant was a clouds plant and could make magic clouds.— Tommy
- I thought the white circles you see when looking at a bright window were what atoms of air look like.— H.
- 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 always thought that everytime it got cold or snowed, the plant Neptune came closer to earth.— Andy T
- I once knew a girl who used to believe that the sun was actaully a really bright gold fish very high up.— meow
- I thought the big hand was for the hour and the smaller one was for the minutes until i was in third grade.— Time Challenged