Hi Mary,
" Had a bad time with a brand of seeds last year. Any seeds that are large enough to see (ha), I sometimes give a quick soak in peroxide water before planting. Seems to work well even in older seeds. "
I don't know about all seeds, but I think most, if not all, commercial zinnia seeds have been heat treated to kill diseases on the seeds. It's tricky doing a heat treatment without killing the seed, but they carefully control the temperature and the duration of the treatment to get the job done. These are some of my current indoor zinnia seedlings.
I planted some more zinnia seeds today. I have been told that you should, as a rule of thumb, consider all seeds that you save yourself as contaminated with disease. And that you should treat your saved seeds to disinfect them. I would never attempt the heat treatment -- I would just end up cooking my special breeder zinnia seeds. But I do use either Peroxide or Physan 20 on my zinnia seeds, in the planting medium, to treat my own seeds. If I forget, usually a quick seedling death from Damping Off reminds me that I forgot.
ZM
