It is shaggy portulaca, Portulaca pilosa, a low growing trailing succulent. It is an annual but the seeds, which are formed in cup-shaped capsules, overwinter and seem to spread readily. I first noticed it growing in the decomposed granite out front. The flower only opens in full sun but then that isn't a problem here in Texas!
I later noticed the plant growing in one of the vegetable beds and mistook it for the much larger flowered portulaca I have. The leaves are similar but somewhat narrower.
|Large flowering Mexican portulaca.|
On this west facing wall, where temperatures are hot enough to fry an egg, I am happy that this little plant likes its new home. I am thinking that it would also make a nice rock garden addition.