Portulaca grandiflora http://www.durgan.org/ShortURL/?JJZFQ 12 July 2008 (Portulaca grandiflora) Portulaca grandiflora- moss rose, garden portulaca, garden purslane. This plant self seeds in Zone 5. It makes a great fill in any flower bed, and its foliage is a great moisture retainer. Watering almost immediately destroys the plant. It thrives in droughty or very dry conditions.