Gardening IS broken in the game. Ever since the first CL patch I've noticed that if it's Spring in your game, weeds and bugs will spawn multiple times a day on every plant, and even on World plants, the latter of which is irritating, since your Sims don't have any options to remove those.
If it's any other season than Spring, then they don't spawn at all, so as far as a player will be concerned, those problems aren't occurring.
The weeds/bugs problem during spring occurs even if the plant is sheltered, which is completely absurd. One of the whole points of greenhouses in real life is the ability to prevent pests.
I finally got to a point where I went through every plant XML file and completely removed the option for bugs to spawn. Unfortunately, I can't figure out what XML (or what point in the Plants XMLs) controls weeds, so those still spawn incessantly. The fact that they spawn even on world plants, which my Sims can't do anything about, means that during the entirety of spring, every world plant has weeds choking its roots for the entire season.
Upshot is that I've decided not to do any gardening for any Sim at all anymore, because I don't want my blood pressure and stress levels to continue going up from it. This means that I will never use the Simple Living challenge trait, because I can't. Not until gardening isn't so completely broken.
I'm not surprised to hear that the bunnies/birds only deal with pests on the CL patches. That's also absurd, but it's in tune with EA's typical assertiveness that we MUST always use the latest of ANYTHING if we want anything to get done. I have CL, but I'm not about to allow them to browbeat me into submission in that manner.
I hadn't thought of using Florilorial to clear out pests, but it's a good idea. @bshag4lv, thank you for that idea; now to just determine the range of that spell, and at least my spellcasters can go back to gardening.