I happened on your site while trying to search for the type of spider I found in my garden last year (actually, in the plants that grew out of the compost pile). I’ve never seen a spider like this in this area before (Northern Massachusetts) or since. I don’t have any good size comparison in the pictures I got except that those are pumpkin leaves he’s (she’s?) on. I would estimate the diameter of the circle formed by the legs was about 3 inches. anyway, if you could identify this spider for me, I’d appreciate it.
We have lots of photos and information on the Golden Orb Weaver, or Yellow Garden Spider, Argiope aurantia or Miranda aurantia, on our two spider pages. We agree that this spider is always startling to see, but though it can bite painfully, it seldom does. Your female looks very mature.