I have gotten fresh lemons before and put them in my fruit bowl, and a couple of days later, they have green mold only on the side facing down. I thought it was an oxygen thing, so I always move my lemons every day or two to stop this, but apparently that doesn't work anymore. Also, I just read that refrigerating lemons helps extend their shelf-life. I literally didn't know you "needed" to refrigerate lemons, but I guess I'm going to start now. I just had to chuck 3 perfectly good lemons because they got moldy unbelievably fast.