They are portulaca (moss roses) and they do readily re-seed each year. I had a bunch of them pop up in old potting soil I brought with me when I moved last fall. I dug them out and planted them along the edge of my bed by the street and they are doing great. I also planted about 100 Yubi Portulaca in a huge natural area near our cul-de-sac. They are smooth, glossy flowers but also have flat, rubbery leaves that are not hairy looking like the moss roses. The Yubi's also reseed and I'm planning on them coming back next summer. They love full, hot sun and require very little water. I own a flower planting business and I used Yubi's for a customer on a busy cobblestone sidewalk that had a statue and a bed surrounding it. It was near a business and did not get regular waterings. Last summer we were in a severe drought and they went nuts. The customer called me at the end of the summer and asked me what they were. Well, this summer we're inundated with rain and I drove by her statue. It was filled with Yubi's again. Reseeded from last year.
I found this growing down my street underneath some mailboxes. I think
> the city planted it.
>
>formatting link> They planted it underneath the mailboxes last year so that it filled
> the space, about 6 feet by 2 feet. They pulled it out at the end of
> last season. This year they planted geraniums and day lilies. However,
> it's growing back from last year. I am unsure if this is due to
> re-seeding or if it's regrowing from old roots. It is actually even
> growing out of some of the cracks in the surrounding pavement.
>
> As you can see from the pics, the flowers look poppy-like and are in
> shades of white, orange, yellow, and red. There are no leaves; the
> foliage is soft with thick, fleshy spines, like anemone.
>
> So far no luck in trying to find out what this is. All the poppy pics
> I've looked at have flat "regular" leaves.
>