I eventually had to get high enough gardening to take cuttings of plants, and it was necessary to make many all nighter visits to the lots with pears, cherries, blackberries, lemons... in order to get those. I got 'lucky' with sage and was able to harvest it.
After playing several more game weeks, the pears have finally become harvestable in places. I have the reward for not needing sleep (first one I bought), and I tend to stay out all night when gathering, and for the 5am rollover so I can double-gather on dig sites. I am not sure that this helps with plant growth, but I tell myself it does.