This story is actually two of my mom's childhood beliefs. When she was about 6 her parents decided to give her her very own plant to take care of (still too young for her own pet). They said that adding a little sugar water to the pot would help it grow, and so she concluded that meant all seasonings would help it. For a little while she sprinkled sugar, salt, and pepper in her plant - which of course killed it. For many years afterward she was convinced that she could never have a plant again because it would "know" what happened to the last one and die as punishment. To this day, she really does still have a "black thumb" and is terrible with plants.
A childhood belief about plants

others believed things like this
- adding too much sugar to foods would give you "sugar worms"...
Anon - When I was a kid I took two showers becaue I thought my hair was a plant and needed the water to grow— Tim
- When I was a kid, I used to believe a nuclear plant was a clouds plant and could make magic clouds.— Tommy
- if you eat a seed, the plant will grow in your tummyAnon
- I used to believe that if I ate a fruit's seeds, a plant would grow in my stomach.— Natalia Castillejo
- My mother convinced all of us kids in our family that the large rhubarb in the garden was a Man-Eating Plant. — H.Miller