One possibility that comes to my mind is that there was a seed from another species of this genus in the mix. There are a couple of perennial species (perennial in their own habitat) that form bulbs (caudex?) at the base.
Here is a link I found to some flowers

Here is a link that might be useful: Ipomoea

Hmmm...that takes me to a PDF file on "RNA Interference Resolution!" I put a pantyhose "sack" around the seed head to be sure to get the seeds. Nothing in my plant books under ipomoea looked like this flower, but the pic's weren't the best.

hmmm not sure how that happened, probably a cut and paste error. I can't find that page again, so here's another one , with different species names. You can do a search and get a feeling of how many different ones there are. Not sure if this page lists ALL species, but there are a couple ;-)

Here is a link that might be useful: Ipomoea

thanks!

Hi,

Could it be a moonflower, Ipomoea alba? Good Luck with identifying it.

Danita

Danita, we did plant some morning glories that were listed as "moonflowers" but we thought they were the ones that were white and had a more pointed seed capsule. This one weird one had a really long flower and large capsule. It is possible that the other white ones are just white morning glories and the weird flower is a true "moon flower." Without comparison I don't know and this is the first year we've grown any morning glories of any kind. You could be right about this.

Your description of the really long flower and the large seed capsule sounds like moonflower to me. My moonflowers developed large, acorn-size, purplish pods. The flowers were white, and appeared to be twisted before they opened. They open at night and are fragrant.

Jen26, that sounds like what we've got.