This gardening topic concerns growing vegetables that are native to you specific micro-environment. Gardeners all around the world begin this process accidentally, as some vegetables they do not pick, mature in the garden, grow old and decompose, leaving seeds behind. In the Spring of the following year, those seeds come up like crazy, and most gardeners chop them out as they are considered no different than weeds. Those plants are known as "volunteers," as you did not plant them on purpose, but are the freely given offspring from last year's plants. Here is a technique I've employed successfully, to make the most of those volunteers:
Plant your garden normally, making sure that most of your garden is sown in open pollinated (non-hybrid) seeds. Let the plants grow up becoming adults. Before harvesting any open pollinated crop, be a detective and locate the best-looking, most robust, disease-and pest free individuals of each the variety of vegetable. You can pinch off a bit of them to make sure the taste is at the top of your standards. So, what you are looking for are plants that you would like to see next year in the garden. Don't harvest those specific individual, robust plants that you've selected, but let them grow up for several more months so they produce flowers. When fully bloomed, you may want to help in pollination so as to ensure good seed production. In another couple months you can harvest the seed for next year if you like, but certainly some seeds will of fallen back into the garden beforehand. Also, your plants are probably full of thousands of seeds, so collect the amount you need for next year and then pull up the plant, and shake the rest of the seeds throughout the garden. These seeds will sprout up and grow in the Spring.
Now, when you see these new spouts coming next year, and you know they came from parent varieties you selected, do not weed them out, but let those individuals grow up too, and disperse their seeds once again.
The healthy varieties, adapted to your specific micro-environment, will survive from year to year. Always weed out any individual plants that show signs of weakness or disease, as you do not want them to produce seeds and pass on those traits into the gene pool you are developing. And most important, be a good weeder and chop down any undesirable plants before they go to seed, as you do not want weeds to take over your garden. In fact, a rule of nature, is that she will do her best to cover up any exposed, open, fertile soil with plants. We are trying to use this rule to our advantage here. If we can keep the weed seeds out of the garden, and keep the vegetable seeds (that we have personally selected) in and throughout the garden, then over the years the garden will grow a lot of vegetables, as if they were weeds.
I've done this technique for many years, and now have many types of lettuce, basil, squash, beans, sunflowers, Swiss chard, broccoli, tomatoes, etc., come up where the weeds use to be. But these vegetables, are just not any old, bad-tasting things, but specific varieties that I have selected and helped along. Again: you have to be vigilant in checking out the individuals you save. Make sure they are robust in growth, taste great, look good, and have no problems with disease or pests.
This is an obvious good survival technique for after the pole shift as you can image having vegetables come up where and when weeds naturally grow. You will find, just as I have, that this technique will put food on the table, many days of the year, without you having to work at it.