We lived in Phoenix, AZ for 22 years and the city is full of orange trees planted in public areas. These are the Seville oranges that are used in making marmalade. They have to be picked up by the maintenance workers because they are not fit to eat fresh. I often wondered why they wouldn't have planted juice or navel oranges instead as people would have been glad to have them. I always had a great supply source for making marmalade and often used the zest from these oranges in my baking.