I didn't even know we could Shift+Click on the plants. :open_mouth: Gardening isn't quite as much fun as it was prior to Seasons, I'm sorry to say. Finding the things I need for my vegetable garden used to come down to scouring the neighborhoods for wild plants that were in need of harvesting and then planting the harvested item. One isn't always lucky to receive the seeds in any given pack. I do enjoy the additional things we can plant, however. But keeping my stuff in the Green House I built means the plants don't need as much attention as before. In some ways it's nice, in other ways, it gives my Sim less to do when the rest of the household is at work or school. Hm. Perhaps, we're both (my Sim and I) neglecting the laundry …
As to your direct question, have you or is it possible to select something from that menu? If so, select Mulched and see what happens. Perhaps, they have come up with a more direct way to fertilize our plants, other than using fish or various other harvested items.