A grass, Stipagrostis sabulicola (Poaceae), and a succulent, Trianlhema hereroensis (Aizoaceae), constitute the persistent vegetation of the western half of the main Namib Sand Sea. Following unusual, heavy rainfall (>100 mm), germination of both species occurred over most of the bare dune sand. However, after 11 years of measurement, only 11% of the originally established grasses and none of the succulents survived. Sand mobility or moisture rather than seed availability is thought to influence the plant distribution patterns observed.