Gotta love those volunteer plants. I have one volunteer hill. Have a lot of volunteer potatoes. I transplanted most of them to get them out from under foot. always have volunteer dill, and let my lettuce go to seed every year. Radish seed pods are tasty little buggers also, but they don't breed true. I also let my parsley over winter so there's a crop of early parsley followed by seeds the following spring. Garlic scapes, if left in place will form little bulbils that will fall to the ground, or can be picked and planted where you want a new crop of garlic. Calendula, and nasturtiums are also good propagators also.