Please use this thread going forward: Quality of plants not/very slowly progressing/ No evolve | EA Forums - 11945515
I'm also having this problem.
My sheltered plants are evolving incredibly slowly. My game has been active for 2 sim years, and in that time, I've been watering, weeding and talking to my plants daily, and fertilizing whenever it's available. I only have 3 plants at excellent quality, and the rest are stuck in the dead zone between Nice and Excellent.
Subjectively, I think the plants outdoors are evolving a little faster, given that they spend a chunk of their time in dormant state but are more-or-less on par with the sheltered plants in terms of progress (all in the Nice-Excellent dead zone).
I also found that splicing a plant resets its progress for that evolution stage, but I'm not sure if that's a feature or a bug. Annoying either way, though.
