One characteristic of a sustainable garden is that it produces at least some of its own seed. There are flowers, herbs and vegetables that self-seed. Some produce seeds so readily that as long as you give them time to flower and mature, and set seed, you'll always have free plants growing in your garden.Amy Ivy, horticulturist with Cornell Cooperative Extension in Clinton and Essex counties, says self-sowers may be annuals, biennials, or perennials. With a bit of light management, each generation can be coaxed into providing seeds for many seasons. And gardeners can collect and save seeds until the following year. [full story]