Hybridizers: It can be fun to breed your own zinnias - Part 4, 1 by Zen_Man

Zen_Man wrote:
Corey,

Back to the subject of your zinnia blooms being flat and daisy-like this year, instead of spherical. When a zinnia bloom first opens, it is single, because it hasn't had time to put out more than one row of petals. As it adds more rows of petals, the bloom becomes deeper and the overall shape of the flower becomes more spherical. All of the blooms in this picture are on the same zinnia plant, which in this case is a marigold flowered zinnia similar to the carnation-flowered marigolds. Those blooms are in various stages of development. So it may be that your zinnias this year just didn't have enough time or energy to form as many rows of petals as they could have.

ZM