From time to time I hear from people who are interested in finding alternatives to chemical-based products to use as fertilizers or for weed control. One such enquiry came from a reader who signed the e-mail "Green Duck," and said: "I have a well system for drinking water and do not want to use chemicals on my driveway or in my yard. Do you know where I can find (or how I can mix my own) natural ways to kill grass where it's not wanted (flower beds, driveway, etc), natural poison ivy killers and weed killers for my lawn, and natural plant foods for fertilizing pine trees, flowers, vegetables...