Lemons are just about everyones favorite, and the seeds from them are probably the easiest to save.
You will be better off saving self-pollinating vegetables, so the cross-pollination process doesnt get too involved.
With a self-pollinating variety, your seed will come true next year with no problems.

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The other easy seeds to save are grapefruits, oranges, tangerines, clementines, and limes.
When the seeds start to sprout you will plant them in rich potting soil.

