Mesembryanthemum is a genus of flowering plants in the family Aizoaceae; like many members of this family, it is characterized by long-lasting flower heads. Flowers of Mesembryanthemum protect their gametes from night-time dews or frosts but open in sunlight. There is an obvious evolutionary advantage to doing this; where sun, dew, frost, wind or predators are likely to damage exposed reproductive organs, closing may be advantageous during times when flowers are unlikely to attract pollinators. It is indigenous to southern Africa. Many Mesembryanthemum species are known as ice plants because of the glistening globular bladder cells covering their stems, fruit and leaves,”… they sparkle like ice crystals”. In South Africa, Mesembryanthemums are known as “vygies” (from Afrikaans “vy”), although this term refers to many plants in the family Aizoaceae. Many succulent growers refer to them as mesembs. Species formerly placed in Mesembryanthemum have been transferred to other genera, such as Cleretum, Carpobrotus and Sceletium, although sources differ.

Mesembryanthemum viridiflorum, synonymously known as Aridaria trichosantha, Aridaria viridiflora, Mesembryanthemum trichosanthum, Mesembryanthemum viridiflorum, Nycteranthus viridiflorus, Perapentacoilanthus viridiflorus, Phyllobolus viridiflorus or Sphalmanthus viridiflorus and commonly known as Clanwilliam Mopkop, is a rare South African endemic species found in the Western Cape province occurring in the Olifants River Valley. It is a small ground sprawling succulent plant with succulent leaves and yellow flowers.