You can't get much more eat-local than growing your own food in your own backyard or in containers on your apartment balcony. But how? Northhaven Gardens, a long-tenured plant nursery next to the Jewish Community Center just off Central Expressway, has taken on a kind of second persona as a center for urban sustainable gardening. They sell everything from the right plants to the right mulch for the plants, but they also do much more. They hold weekend seminars on urban chicken-tending, for example. These events invariably blossom into high-spirited country fairs for city people.