Spinach can grow quickly in the home garden, and often gardeners can successively plant spinach to get a continual harvest. Spinach plants produce separate male and female plants. They are pollinated easily by the wind, which can carry the pollen for several miles. Spinach plants typically produce seeds about 4 to 6 weeks after leaves have been ready to harvest.
One small crop of spinach plants can provide you with enough seeds for several years of garden growing, and can be stored for use for up to 4 years.
Harvest individual leaves by cutting them with scissors at the point where the base of the leaf meets the stem. Avoid pulling up the plants to harvest them so that they can develop seeds. Let your plants brown and begin to dry once there are no more leaves to harvest.
Identify which plants are male and female. If you see little yellow balls underneath the leaves this is the male plant. The female will have larger round-shaped green balls underneath the leaves. One female spinach plant may produce hundreds of seeds, each of which are about 1/8 inch in size.
Pull up your spinach plants once they have dried out. Typically, seeds are ready to harvest about 1 to 1 ½ months after you've harvested the leaves. Discard the male plants. Hang any female plants that haven't fully dried out upside down in a cool and dry location for a week.
Put on your gloves. Rake your thumb over each female plant to loosen the seeds from the stem. Catch your seeds with a paper bag as they fall.
Store your seeds in a sealed glass jar and label it. Place the jar in a cool, dry place.