We started our winter garden back in July: leeks, kale, brussels sprouts (above), cabbage, salsify, radicchio and chard, among other plants, all started from seed beneath the ripening tomatoes and the heavily laden bean vines. And we planted garlic in the fall at the same time as all the other bulbs.
Some of these plants - chard, spinach, corn salad, radicchio, endive and various other greens - don't last through a solid frost, but we've been eating them through the fall. We've also been eating the kale, which will last through winter here on the West Coast (unless it gets really cold), and have been harvesting the cabbages, too. If they're not eaten right away, they can be wrapped in paper individually and stored in a cool place for a number of months to come. Save the brussels sprouts to harvest until Christmas dinner - you won't regret it, I promise.
On beds without winter crops, we've weeded and top dressed with manure or compost - and planted a cover crop. We also kept some of the chickweed in a couple of beds where it grows most heavily: even through the winter, it grows and bears fruit, and it's a great winter tonic in times when the other greens aren't available - full of vitamins! It's crunchy and a little bit tough, but mild-tasting, and makes abgreat salad topper. (And if we don't eat it, we give it to the chickens by the handful. They fall on like a pack of starving ... um ... wolves? Heaven forfend!)
In any case, the idea with fall soil preparation has been to feed it while only disturbing it minimally: we didn't want to dig it over, as the beneficial critters like earth worms and other insects will be disturbed at a time when, with the cold, their lives are more stressed. As well, the soil has established a layered fertile microcosm, which if disturbed too much, will only have to re-establish itself before the soil will be at its food-growing optimum again!
Now is also a good time to test the soil pH levels - most West Coast soils are on the acidic side, due to the amount of rain we get, washing the "salts" out. You can buy kits at a gardening store or get the soil professionally tested for a fuller soil profile. Most vegetables grow well in a pretty neutral soil, while some, like potatoes, prefer it mildly acid - and plants like blueberries really like it acid! If you want to try to balance the pH, though, wait until about 6 weeks before planting in the spring. The easiest method is to sprinkle dolomite lime on the beds, or beneath the relevant plants, and the 6 weeks gives the lime time to wash into the soil - but not time to wash back out again! Lime is easy to find at any gardening store.
For high-acid plants like blueberries, you can top-dress in the fall, with something like evergreen needles. Don't bring the needles right up around the stem - leave about 6 inches in all directions - and spread the needles out to the drip line. You can also use peat moss - but peat is harvested from some of the rarest and most fragile of ecosystems (peat bogs, of course!), and we strongly recommend not supporting such a damaging practise. Strongly. And in a total pinch, you an use an azalea/rhododendron fertlizer, but that's not exactly organic .... Oh! one last tip: don't put manure around the blueberries, since it's actually rather alkaline, and isn't helpful to them.