Where does silk comes from?

My knowledge is so shallow. All this while I thought silk comes from silk trees until some one told me that she has a silk tree at her house for decoration. I told her, that it must be expensive to own a silk tree, you know, we get our silk from it. Like having a gold tree in your house. She laughed! Wei! The silk dress that you wear comes from the silkworms not trees!!! Really??? And and...silkworm eats Mulberry leaves not silk tree leaves.