When I was at infants school one of the first things we did was grow mustard cress to make our own sandwiches. I never understood how they got the mustard into the cress while it was growing.
Similarly I always thought "egg and cress" sandwiches were "egg cress" and that was a different type of cress which they put eggs in while it was growing.
I still don't really understand mustard cress.
A childhood belief about plants

others believed things like this
- My mom used to tell me if I ate mustard I would grow mustard.Anon
- My friend believed that eating bread crusts or eating mustard will give you curly hair.— Linda from Southern California
- the beatles song 'mean mr mustard' says "shes a real go-getter", i was sure it was "shes a real coconut"...— sally
- I thought that barf was what they used to make peanut butter and jelly sandwiches!— Maan o' War
- I used to believe eating the crusts from sandwiches would make my hair curly.Anon
- I used to think that growing pains meant that a tomato plant was growing in your stomach.— Annette