There are some special considerations when growing heirloom vegetables for food and seed in small plots. If you intend to save your seeds from at least some of your vegetables, you will need to do some things to make sure you get pure seed. Vegetables of the same species, such as tomatoes, will cross pollinate each other if grown too close together. The distance varies from a few yards for some vegetables to over 1/2 mile for corn.
While people with a large acre plot may be able to spread out their tomatoes, peppers, and other things by variety, someone with a 4X8 raised bed has a problem. You basically have three options. The first, and least satisfactory, is to let the varieties cross pollinate and see what happens. You might get a good result, you might not. The seeds will not breed true to the parent, however, so the results are rather unpredictable.
You can plant your varieties as you normally would and place pollination nets over them. These exclude pollinating insects and the wind and keep the pollen from spreading to other plants. The down side to this is that you have to pollinate your plants by hand. This can be labor intensive, but does allow you a lot of control over what plants produce.
Finally, you can choose to only grow one cultivar of each vegetable. Then there is nothing close enough to cross pollinate most crops, unless your neighbor is growing the same things very close. This does limit your selection of produce, but perhaps you can grow different varieties in the spring, summer, and fall garden to see which ones suit you best.
Heirloom vegetables are fun to grow. People often forget, however, that they are only going to stay heirloom vegetables if you keep them from crossing with other varieties of the same vegetable. This makes heirlooms a little more work, but they make up for it in taste if they are grown right.
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