Buying new seeds every year is costly, so it makes sense to save your own seeds where possible. Note that you cannot save seeds from F1 or F2 hybrid varieties as these do not produce viable, fruit-bearing or flowering plants the following year. Methods for saving your own seeds vary depending on the type of plants. Seed saving also helps to preserve rare seeds and heirloom varieties that may otherwise be lost.
Leave a portion of the beans, equivalent to the number of seeds you want to save on the plant towards the end of the growing season, allowing them to mature and dry out. Once dry, the bean seeds are mature, so strip them from the vines, shell them, and leave them in a cool, dry area. If not completely dry, they'll grow mould when you store them for next year. Consider the type of beans you have. French beans do not cross easily with one another, so you can grow multiple varieties at once - preferably with a bit of space between each variety. Grow extra seeds to allow you to weed out any seedlings that are clearly not viable, or are a crossed variety. Runner beans cross easily - if you plan to save seed, you'll have most success if only growing one variety. Broad beans also cross easily, and need to be isolated from other varieties within a half mile radius, or by putting a few plants you plan to keep for seed in an isolation cage.
Courgettes, Squashes, and Pumpkins
Courgettes, squashes, and pumpkins can readily cross with one another. Instead of letting bees, hover flies, and other insects pollinate the plants, do it yourself. As the flower begins to open, use gentle twine or a rubber band to keep it closed, preventing pollinators getting inside. Take a soft paintbrush and take the pollen from inside the male flowers, and transfer it onto the stigma on the female flowers. Then close the flowers again. Mark the base of each hand-pollinated fruit with a piece of wool, so you know which ones are for seed. Then, once the fruit is fully mature, cut from the vine and allow to ripen indoors for a month. Cut the fruit in half, scoop out the seeds, wash them thoroughly, remove the fibre, put them on a plate on a sunny windowsill or warm, dry place, and dry them completely.
Peas are easy to save seed from, as they are self-pollinating and rarely cross. Simply elect a few of the strongest plants from your crop and mark them for seed, then wait. Leave the pods to fully develop and dry on the vine. Once the pods turn brown, leathery, and brittle, remove them from the vine, shell the peas, and dry them further in a warm area. Once hard and dry, store them in an airtight container.