I don't tend to overwinter much in my vegetable patch as (normally) our winters can be a bit harsh at times and the garden is fairly exposed. Leeks and parsnips do OK and this year I had good crops of brussels and kale. However previous attempts to start onions or broad beans in the Autumn have resulted either in complete failure or certainly poor crops that had no advantage over their Spring sown cousins. Back last Autumn though I did sow something new ..... green manure.
noun Agriculture . 1. a crop of growing plants, as clover and other nitrogen-fixing plants, plowed under to enrich the soil. 2. manure that has not undergone decay.