Other plants are very easy to collect seeds from. Here are some guidelines for collecting the seeds of specific fruits and vegetables. Carrots and radishes will not produce seed until the second year of growth. You can leave them in the garden over the winter with a heavy mulch on the top or you can dig them up and store them in a damp root cellar for spring replanting. At the end of the second season, when the seed head is almost ripe, tie a paper bag over it to collect the seeds and prevent them from falling to the ground.
Cucumbers are ready for seed harvest after they are fully ripe.
Wait until the cucumber begins to turn mushy and change colors. Cut the cucumber in half and scrape the seeds into a bowl. Remove the slimy coating by rubbing them gently around the inside of a sieve while washing them. To remove the slimy coating you can also soak them in water for two days, pour off the seeds and slime that rise to the top, and then rinse and dry them. Eggplant should be left on the vine well past the point where you would harvest it for kitchen use.