Hello Teresa,
I am about to go out in my garden to save a few more zinnia seeds, but I do want to comment on this:
" I usually also grow a mix of the Cactus type. So first question, I noticed I could get the Cactus type in a tetraploid version. I'm guessing this will not cross with the other types? Either way, should the tetraploid version cross with itself or be a seed producer from open pollination? "
First of all, I am totally impressed that you even know about the availability of commercial tetraploid Cactus zinnia seed. I wouldn't know about them if I didn't have the GeoSeed catalog.
I became very interested in tetraploid zinnias a few years ago when it occurred to me that the tetraploid zinnias, with 48 chromosomes instead of the usual 24,
might be resistant or immune to Powdery Mildew. So I inter-planted a bunch of tetraploid zinnias (Burpee's Tetras and State Fair) with "regular" zinnias in a semi-shade spot that was highly susceptible to Powdery Mildew. I expected the tetraploid zinnias to at least show resistance to PM, if not be completely immune. Sadly, they were just as covered with Powdery Mildew as their diploid companions. No PM advantage from tetraploidy at all. So I gave up on tetraploids. If that experiment had worked, all of my zinnias today would be tetraploids. But that was not to be.
But in answer to your question, you or the bees can cross tetraploid zinnias with diploid zinnias to create triploid hybrid seeds. And the triploid zinnia seeds grow nicely to produce admirable triploid zinnia plants. The triploid zinnia plants can even set apparently good seeds. I inadvertently grew a triploid cactus zinnia plant, apparently a bee cross from my Powdery Mildew experiment, and I got a huge seed set from it because it was a huge plant, but none of those hundreds of triploid set seeds germinated. I got
zero seedlings out of maybe a
couple of thousand apparently good triploid seeds.
I gave up on the idea of triploid zinnias because I didn't want to find myself in the situation of getting a fantastic new zinnia with no way to propagate it, other than from cuttings or tissue culture. But there are possible reasons why you might want to produce and grow triploid zinnias, and I will go into that in a subsequent message. My zinnia seedheads are calling to me to come and get them. More later. This triploid zinnia thing deserves full consideration.
ZM
