Silphium was reputed to have birth controlling properties because its seeds were heart-shaped. I was talking about something a little more... reliable... such as, say, Premarin.

You got it wrong. It is the other way around.

There has been some speculation about the connection between silphium and the traditional heart shape (♥). The symbol is remarkably similar to the Egyptian "heart soul" (ib). The sexual nature of that concept, combined with the widespread use of silphium in ancient Egypt for birth control, and the fact that silphium seeds were heart-shaped, leads to speculation that the character for ib may have been derived from the shape of the silphium seed.