On June 30th, my summer garden is finished and I start thinking of fall. Or rather, on June 30, I stop planting the summer garden. Where I live, the last frost date is fairly late in May (22nd this year), and it often isn't reliably warm at night, the way things like peppers, eggplant, melons and okra like it, until the middle of June. Which means that while I start planting in late March or early April, I'm usually still cramming extra hot peppers and heat loving flowers into beds until the very last day June. And on July 1, I turn to beginning the fall garden beds, and planning for an extended harvest.
So far, climate change seems to be making the northeast (or at least my part of it), much more like the Pacific Northwest. Winters are milder and warmer (Over the last 5 years, I've managed to winter over kale completely uncovered 4 years out of 5, leeks 3 out of five and spinach twice, which is really quite remarkable in a place whose traditional lows run around -25 degrees), and all year 'round is rainier. While we've had some warm periods in the summer, the wetness seems to mean that overall, our summer temperatures are pretty tolerable. Because of the heavy rains of spring, even slightly warmer spring temperatures don't mean I can plant much earlier in the year. Butit does mean long falls, later first hard frosts and long seasons of being able to pick frost hardy greens. In past years, most of my garden has been finished by the end of November or beginning of December, but this year I was picking garden greens well into January.
Which means, if you think about it, that the fall gardening season is as long as the summer one. But comparatively few people grow fall gardens - at most when you drive around you'll see a few brussels sprouts plants. Most people in my region, even the most dedicated gardeners, are relying on the grocery stores or their own home preservation for several months when they could be eating fresh food grown in their own gardens.
Another reason to think about a fall garden is that frankly, fall gardening is much nicer than summer gardening. The disease and bug problems often seem to just go away. The weather is crisp and pleasant. If you have to put something up, the fire on the woodstove or the heat of the dehydrator is welcome, rather than annoying. And, if you were busy or away back when it was time to get your tomatoes planted, you can still go ahead and plant an autumn garden.
So what goes in a fall garden? There are really two categories of things. The first are traditional summer crops that aren't frost hardy, but have a nice short season, and can be planted in high summer for harvest close to the first frost. For example, this would include bush green beans, very short season determinate tomatoes (assuming you started them ahead), cucumbers, zucchini, potatoes, day neutral onions (some onions require light of specific lengths to bulb up, and they won't in the fall, although you can eat them as scallions). This might also include peppers and eggplant that you plant in pots (although again, you'd have to have started them back in May if you live where I do), and bring inside for their final fruiting in a sunny window.
The second are crops that are frost hardy - that is, things that will take a light or heavy frost and just keep on going. This category includes most of the brassica plants (kale, broccoli, cabbage, brussels sprouts), most root vegetables (carrots, parsnips, turnips, beets), peas and fava beans (not other kinds of beans), and many greens - spinach, lettuce, arugula, mustards, mizuna, most asian greens.
The issue in the fall, at least here, is not so much heat, as light. Most of the crops in the paragraph above will endure quite cold temperatures - eventually they'll succumb, but they can hold out for a long time. But there isn't enough light here after mid to late September to get plants to grow much. People who live south of me will have more luck, but around here, only spinach can be planted as late as September and still fully mature. So in order to have winter crops, we need to get them through most of their major growth in high summer, while the light is potent.
In some places, and some years, this presents a serious problem. Because most of the frost hardy crops don't really like hot weather. They tend to bolt (go to seed) prematurely, or they simply don't flourish. I find that it makes the most sense to start most of the ones that take a while to mature (peas, favas, cabbage, etc...) indoors. The roots generally can take our heat, and so can things like broccoli. But spending a week or two in the cool of our house makes a big difference in long term survival rates, I find. If your house tends to be really hot, a shady outdoor spot might be better.
So most of those things are started indoors in early July, for transplanting as space becomes available. Parsnips and brussels sprouts are particularly long season crops, and those I generally started back in late spring. But I still will probably plant a few more of an early brussels and parsnip.
This year, I have two beds available now - a crop of summer greens planted in May is now done with, and another bed was never planted - a local wren decided to make her home among the thistles, and we had to let her babies fledge before we could do anything. So (after some extensive weeding in the latter case), as soon as I get around to it, I can start planting pickling cukes, green beans, cabbage, carrots, beets, kohlrabi and broccoli for fall. I'll wait on greens and other delicates until the end of the month. Other beds will come available when I harvest our garlic towards the middle of this month, when the first crop of fava beans finishes up, and at the end of the first crop of sweet corn. I'll probably pull up some zucchini plants as well by August - we need the extra early on when they first start producing, but by mid-August, they are just an embarrassment of riches.
The other crop I'll be planting as beds open up are green manures. These do more to enrich my soil than any other amendment. When one of the garlic beds opens up in July, it will go into buckwheat. Not only will the buckwheat make a superb green manure, but until I scythe it down, we'll eat the leaves in salads - they are delicious. If I get lazy and forget to scythe it, like I did last year, it is a tasty grain source.
Later in the season, I may plant sweet clover or winter rye, which will hold the soil together all winter. I can also plant grains for overwintering - rye, of course, and winter wheat. If I plant them in mid-september, I can sometimes even cut them back lightly, feed the wheat grass to the chickens, and still have them make a crop in the summer.
The key to fall gardening is experimentation - ask other local gardeners when they plant things for autumn. It has taken a good bit of practice to come up with fairly optimal (and I'm still working on it) sowing times for many of the fall crops - cool enough to keep them alive through summer, early enough that there's still some light left.
I can also use season extension techniques, like cold frames and heavy mulch to extend the life of things. An easy way to make a cold frame is to put an old window (no lead paint!) on top of a few bales of straw and plant into it. There are more complicated options as well, and nicer looking ones, but that will do. The nice thing is after a year or so, the straw will decompose and with some amendments make a nice basis for a raised bed.
I do some of this, and am hoping to add a hoophouse, but I'm increasingly impressed by how hardy many plants are on their own, needing nothing more than a bit of mulch on the coldest days to overwinter nicely. Specific varieties are particularly hardy - Blue de Solaize leek, for example, seems to overwinter nicely, Marvel of Four Seasons Lettuce and the Oak Leaf and Deer Tongue lettuces do nicely here, as does "Winter Giant Spinach" and several kales "Winterbor," "Red Russian," and "Dinosaur." Some people are working on breeding winter hardy vegetables - Fedco offers seed for "ice-bred arugula" and a variety of collards designed to stand the whole winter.
Eliot Coleman's book _The Four Season Harvest_ is *the* book on Northern season extension. Those of you who live in different climates will have to look around for your own. Many of you grow a lot of your food in the winter already there. For those who have thought their climate was simply too cold for autumn planting, you might consider experimenting with the fall catalogs that some places, like Territorial Seeds, offer.
I would also add that if you looked at the list of food that can be grown in fall above, and thought "Oh, I don't like all those greens" - try it. Cold weather turns the starches in many of those vegetables to sugars, and they have a sweetness and depth of flavor that is hard to imagine if you've been getting your vegetables from the supermarket. Cabbage we ate in December last year was the sweetest thing I can imagine eating. Eliot Coleman calls his winter carrots "candy carrots" because they are so sweet. Unless you've had brussels sprouts picked hours ago and eaten after a good hard frost, you don't really know what they taste like. And that's another reason to garden in fall - because if you don't, you are missing out on real pleasures.
I would strongly recommend that everyone south of zone 2 seriously consider planting food for fall and winter in their gardens. As much as I love the hearty things I root cellar and the food I put up for winter, there is nothing like crisp greens and fresh salads when the weather outside is frightful. It can be hard, in the heat of summer, to start planning for the days of cold and winter, but that's the truth of this lifestyle - you live in the moment - but the moment is eternally, inevitably, cyclical.