One of the many orb weavers but obviously not currently in her web. She's quite pretty, isn't she?

The orb weavers make a large flat web that resembles a multi-spoked wagon wheel. The spider hangs upside down in the center during the evening but usually hides during the daytime, staying somewhere to the side of the web.

Guessin' Shamrock Orb Weaver (Araneus trifolium)?

Good guess! I never the Shamrock, but I did a Google Image search and found lots of his/her relatives in various colors and shapes. I'll read up on them.

I should have recognized the "orb weaver" part, but I was put off by the appearance of a web on the leaf.

Thanks, both of you!

Here's a closer look: