Examine the neck of a cockscomb plume for seed development. The seeds are tiny black-gray rectangle shapes that appear approximately 90 to 120 days after germination.
Assure that seed development is complete by placing a piece of white paper under the neck of the plume and scraping the seeds with a quarter or a fingernail. Seed development is complete when the seed falls readily on to the paper.
Snip the cockscomb plume away from the plant using garden scissors. Take care not to disturb the seeds.
Allow the cockscomb seeds to dry completely by placing the plume on a large piece of white paper in a cool, dry place. This process can take several days or a few weeks, depending on the humidity level.
Shake the dried plume over the white paper to release the seeds. If the seeds do not shake out easily, scrape the seeds away from the plume using a kitchen knife or quarter.
Store the seeds in a paper envelope or glass jar in a cool, dry place. Use the seeds within two growing seasons to ensure viability.