take three circles, smash them together, and what do you get?
Now, take a look at the middle portion.
that's a triquetra!
now take four (crappily drawn) circles
Highlight the middle portion
does THAT look familiar?
you bet it does!
A flower is just a circle folded in on itself, the amount of petals on a flower shows how much it was folded in on itself! For example, a four petal flower has been folded four times, at the tip of each petal. If you took the outside points of a flower, and reversed them, you'd have a proper (rather large) circle!