Fun to see this thread pop up. I grew the edible variety this summer. I never saw it bloom but would find seed pods. I dug up one plant and it is still growing now with protection from frosts.
This is where I found the seeds...
http://store.underwoodgardens.... (Sorry but I see it won't link to the specific page, just search for purslane in the search box.)
and this is a photo of a plant. The stems are red but quity stocky compared to the wild or ornamental purslanes.