Mendel's rules do not apply to Plant Tycoon, so all the seeds from a "cross" are the same. It's not like crossing genotypes, but more like mixing paint colors: You mix red and blue paints and get purple. Purple paint stays purple. You can't get red and blue back from mixing purple with purple.

That only works with co-dominant "red" and "blue" alleles following Mendel's rules in real world genetics. You can cross red-flowered sweet peas and blue-flowered sweet peas to get purple-flowered sweet pea plants. When you self-pollinate those, you get 25% red-flowered, 25% blue-flowered and 50% purple-flowered peas. Plant Tycoon "genetics" does not work that way though.