Hello Maryl,
" I was surprised a couple of years ago that I wasn't able to get many of the single colors of the Parks Dreamland or Magellan seeds any longer. "
Dreamland is not produced by Park Seed, or exclusive to them. They just buy it in bulk from the Japanese breeder, Takii, and put it in their own seed packets. That is not dishonest, most of the retail seed companies do that. This is a list of seed companies that sell some of the Takii seeds.
https://www.takii.com/flowers/...
I don't grow the shorter zinnias, so I don't grow Dreamland or Magellan. I guess you could say that White is my favorite zinnia color, and Dreamland does not offer a true White. The closest it has is Ivory. I think Magellan may have a true White.
" The disease resistance on the Magellans is especially good in my climate. Sad really that you can't seem to ever get the original series characteristics back from seed"
It is true that F1 hybrid zinnias do not "come true" from seed, but if you grow a lot of them and keep only the ones that are closest to the originals, you can "de-hybridize" them to something that comes true and is similar to the original F1 hybrid. You might have a lot of variations and, among those, you might even find some that you liked better than the original F1.
ZM
