Common Lantana

Almost nothing flowers as relentlessly in heat as Lantana camara. Flat heads of tiny flowers open in one colour and age to another, so a single head carries yellow, orange and red together, and in a warm climate the display barely pauses.
The plant is tough to the point of being difficult: it takes reflected heat off paving, poor soil, salt-laden wind and long dry periods, which is precisely why the compact sterile cultivars have become a fixture of Gulf and tropical streetscapes.
Common Lantana is the most productive flowering shrub available for hot, dry, high-exposure planting, provided the form supplied is the right one.