I love Zinnia. While they are an annual (a plant that I generally do not spend a great deal of time worrying about, when I plant something I like it to stay planted and not die come winter), they undergo the most delightful evolution that one can follow day after day. The blooms begin with their main petals, usually bright pinks and yellows and oranges, whether or not they are singles or the more showy pom-poms they begin this way.
As can be seen beginning on this shot, shortly thereafter multitudes of tiny secondary flowers burst from the center filling in the middle until it appears that Ms. Zinnia is wearing a hat of secondary blooms.
This process goes on over time and it is fascinating to watch it go on. As the older outer petals fade the inner yellow blooms seem to shine. While the older petals are busily forming seeds, the yellow blooms continue to attract pollinators and continue to provide food. Finally the yellow tiny blooms begin to form seeds and fade.
If you crumble a dead zinnia head you discover that there are two distinct types of seeds, those that have developed from the first outer petals and those that have developed from those tiny yellow blooms. It really is quite incredible to think that nature developed a process whereby a plant could reproduce itself and then includes a built in back up should there be a shortage of pollinators in a particular stage of its life. I love Zinnia.