This is partially a question, but mostly just a search for confirmation that I have not been able to find elsewhere. My gardening Sim is able to grow Perfect plants without too many issues, but it appears that there is another difference in the quality levels of the plants than the ones listed on Carl's Plant Quality page: number of times the plant can be harvested. I do not have Seasons or Pets installed, but have the other expansions. Anyway, my observations on the issue:
Red Valerian: found a "Bad" quality seed, but since it was the only one I had, I planted it, fertilized, watered and all the rest. The harvest went up a couple of quality levels, as expected, but I was only able to harvest a couple of times before the plant became "Barren". I replanted the Nice/Very Nice harvest and was able to harvest from those four or five times. I'm still waiting on the "Perfect" to see how many times it can be harvested.
Wolfsbane: planted "Normal" quality seed, cared for it and replanted until it was "Perfect" and was able to harvest those plants about seven or eight times before they became Barren.
Plasma Fruit: Problematic, but the idea was to produce my own Outstanding fertilizer. The jury is still out on that question, but it's currently not cost-effective due to low production. The occasional sale at the grocery store, coupled with the occasional Celebrity discount, is keeping me close to the break-even point at present. Anyway, Nice quality plants can be harvested twice, Great quality plants can be harvested three or more times and I'm still waiting to see what happens with better quality, but improving it is taking a while.
Tomatoes: Finally got to "Perfect" and have harvested them five or six times, so don't have anything solid yet.
I've noticed similar with Sweet Grass and Chamomile, but didn't count the number of harvests before removing them from my garden.
Does this match up with anyone else's gardening experience or am I just imagining things? Thanks.