There are two scented geraniums that repel flies and mosquitoes due to their scent. The rose scented geranium (Geranium graveolens) and the citronella scented geranium (Geranium citosun) and I have used both when gardening in the evening. I tuck a leaf behind each ear while I water the plants. There are also the more common ivy leaved geraniums used in window boxes so that you can leave your windows open and keep the flies out. All would be good on your porch so that you can open the screen door and not invite flying guests into your home. Keep growing, Marianne Binetti