Wait for your begonia blooms to shrivel and the attached stems to dry-up, exposing the seedpods. Snip-off the begonia seedpods with a pair of scissors.
Store the begonia seedpods in a paper bag, jar or film canister to ripen for approximately 30 days. Ripe begonia seedpods will turn from pale pink to light brown.
Remove the begonia seedpods from storage after the ripening period. Break the begonia seedpods open over a paper plate, using your fingertips.
Pick-out any chaff that falls out of the begonia seedpods with the seeds. Chaff is the protective casing that covers the seeds that usually has a dry, papery composition.
Place the begonia seeds in a sealed paper envelope. Label the envelope with the seed type and date using a permanent marker. Store the begonia seeds in a cool, dry place until use.