I remember to have planted some crops with q18 seeds and some other with q19 seeds (from a older harvesting, they started Q22 and only went down...). Now I've harvested only q18 seeds but some q19 fibre.

I have more farming that 19, obviously
edit: forgot that, I've just seen that I have some q19 seeds in my bucket. Apparently they went into bucket and then the q18 seeds went into inventory to not mix the quality. I like this feature