MESEMBRYANTHEMUM (meaning "midday flowering") is a genus of flowering plants native to southern Africa. It is a member of the family Aizoaceae and like many members of this family, it is characterised by long-lasting flower heads.
Mesembryanthemum protect their gametes from night time dew 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.
Ornamental mesembryanthemum may escape into the wild and consequently has become widely naturalised outside their natuve range. They are considered an invasive weed in certain places.
My other choice is marigold as, of course, yellow is my favourite colour. I am not absolutely taken with the smell of some varieties and am trying to decide which type I prefer most.
MARIGOLD (Tagetes) is a genus of annual or perennial, mostly herbacious plants in the sunflower family. It was described as a genus by Linnaeus in 1753. The genus is native to North and South America but some species have become naturalised around the world.
The common name in English "marigold" is derived from "Mary's gold", a name first applied to a similar plant Calendula officinalis. The most commonly varieties are known variously as African marigolds (although this species is not native to Africa)
or French marigolds (usually referring to hybrids and cultivars, many of which were developed in France although the species is not native to that country).