Many of the wild flowers in the tropics are yellow. The Mexican poppy, Argemone mexicana has become quite naturalized here . Its spiny leaves warn stray cattle of its toxic nature.
The Black eyed Susan, Thunbergia Alata, is a creeper which twines round wayside tree trunks and hedges.
The Four o'clock flowers colonize empty lots and prove Mendel's theory. There are so many different combinations of colours there.