My Sim only was gardening to have some things to cook with at first, so I started her off with a sage/wild strawberry/spinach/onion hybrid. When it became mature I planted more of it, and grafted other plants on to it to make them perfect from the start. If you wanted, you could start off with a fruit plant, a vegetable plant, and a flower plant, and just evolve these three.
You still do need to some evolving of plants beyond this for the aspiration, but you certainly don't need to go as far as evolving a whole bunch of plants all the way from normal to perfect. I think my Sim just evolved ten plants she had planted once each, and then trimmed leaves from them and hybridized them on to the perfects. If you're trying to level your gardening up quickly, you could evolve them all if you want. It will use a lot more fertilizer, though.