Hybridizers: It can be fun to breed your own zinnias - Part 3, 1 by Zen_Man

Zen_Man wrote:
Hi all,

Apparently our water supply is deficient in boron, and a boron deficiency caused the initial growing tips of many of my young fourth generation zinnias to die. That happened to the zinnia in the attached picture. That had the somewhat fortuitous effect of chemically pinching the plants. I have since supplemented the boron in my nutrients with diluted boric acid to help offset the boron deficiency. I don't want my zinnias to suffer nutrient deficiencies, even if there was a desirable side effect.

I am also making more extensive use of plant growth regulators (PGR) to prevent my zinnia plants from growing too tall. This Summer, if an indoor zinnia grew too tall, I simply moved it outside. That option won't be open this Winter. The Topflor that I use suppresses natural gibberellin production.

None of these compact fourth generation zinnias has a compact parent, even though they look like they must have. I'm still learning by trial and error about using Topflor and other PGRs. One thing I didn't take into account was that the re-used growth medium that I use apparently contains some residual PGR that affects the seedlings that I repot into it. Most of my fourth generation zinnias are pretty well behaved as far as height is concerned. Between the boron problem and my use of PGRs, a lot of my fourth generation zinnias are compact and well-branched, like this specimen in a 5-inch pot.

ZM