From a posting of four years ago [with added asides]:
My Grandmother H [Mary Etta Hall who always signed "M.E. Hall"]* always had a bed of rose moss [Portulaca grandiflora]. For some reason, I didn't think it [could be grown here] until, two or three years ago, I planted a couple of planters with rose moss seed. They not only reseeded within the planters, but have come up as volunteers across the double driveway from the planters and in our strawberry & cherry bed (strawberries fill 1/2 of the bed while a cherry tree and some cherry bushes fill the other 1/2.). This (to the left) is a photo of a golden one--nearly the color of the California poppies--that grows in the edge of the cherry bed, overhanging the apron to the garage.
From today, more photos of volunteer rose moss plant blossoms: