Rachel,

Moonflowers and Bindweed are two different plants in two different Genera, but both are members of the family Convolvulaceae. Bindweed seeds are quite small while Moonflower seeds can be over a 1/4" or 3/8" in diameter.

Bindweed form tuberous roots that can be 5' or deeper underground and are perennial in your area (that's one of the reasons that they're so hard to get rid of) while Moonflowers generally only live longer than a year in tropical/subtropical climates.

I don't think that I've ever seen Bindweed seedlings, but most species in the the family have similar looking seedlings.

How big were the seeds you planted? If they were of a relatively large size, I would think you are safe to assume that that you have the right plants...

Mike

Mike, to be honest I didn't plant seeds. These came from the farmers market with a plant label with a picture and identfying it as a moonflower (I can't remember what the latin name was.) They're still sitting in my kitchen -- planting them moved to the bottom of the list of gardening chores.