Snapdragons (Antirrhinum majus) are named for the unusual shape of their flowers, which open and close like a dragon's jaws when squeezed at their sides. In U.S. Department of Agriculture plant hardiness zones 7 through 10, snapdragons grow as perennial plants, but in colder zones they rarely survive winter. Harvesting snapdragon seeds allows you to grow your own plants in following years -- and you might even grow new varieties, as those grown from seed may feature different flower colors and grow to different sizes than their parent plants. Don't remove fading flowers from snapdragons if you want to collect the seeds.
In USDA zones colder than zone 7, snapdragon seeds are ready for harvesting in fall, but in warmer zones the seeds may ripen in spring. In warm zones, snapdragons are sometimes planted in fall and bloom over winter, which means the seed capsules appear in spring, but in other areas snapdragons flower over summer and fade in fall. Snapdragon seed capsules appear where the flowers grew along the stem. They're ready for harvesting when they're brown and feel papery to the touch.
Pick the seed capsules from the snapdragon stems.
Place the seed capsules on a sheet of newspaper.
Crush the capsules with your fingers or a rolling pin.
Place the crushed capsules and seeds in a coarse sieve, and shake it over the newspaper to separate the seeds from the pieces of seed capsule.
Place a layer of dry rice two or three grains deep on the bottom of a jar to absorb moisture.
Put the snapdragon seeds in the jar.
Seal the jar with its lid.
Write the date and the name of the seeds on the label, and stick it on the jar.
Snapdragon seeds store best in dry, cool conditions. Moisture and warm temperatures reduce the life of seeds. One of the best places for storing snapdragon seeds in airtight jars is in a refrigerator set to 40 degrees Fahrenheit. Cool cellars, basements or pantries are also suitable for storing seeds. In good storage conditions, snapdragon seeds remain able to sprout for three to five years.
In warm zones and rich, freely draining soil, snapdragons self-seed. When the seed capsules aren't removed from the plants, the seeds naturally spill out onto the surrounding soil over time, and grow into new plants. You can collect ripe snapdragon seed capsules and crush them over areas of the garden where you would like snapdragons to grow, or leave the faded plants to self-seed where they grew. When self-seeded snapdragons are growing strongly, remove the smallest, thinnest seedlings to space the remaining plants 6 to 12 inches apart.