I finally got my growfruit to 'perfect' in my regular save! Meanwhile, I did a bit more experimenting in my garden save. I'm still seeing no difference between fresh tuna, growfruit and dragonfruit for my lilies, and my unfertilised perfect strawberry plant is still doing well. I also started three more lilies, one with foul cichlid, one with fresh tilapia and one with normal to nice carrots. The cichlid and tilapia plants are about even (but it's still early stages), but the carrot plant is doing rather poorly.
I also created a spreadsheet with the seasons for all the flowers in the game, and I've been working on a design for a garden that will always have something in bloom. (I'm not very aesthetically gifted - that pond above is way beyond my design capabilities - but I'm thinking it'll be a fun thing to try the next time I have a gardener Sim in my legacy family.)