The hollyhock seeds become ripe at the end of the growing season (usually in late summer or early fall) after the flowers die and leave large, fuzzy, brown pods, which contain hollyhock seeds inside. When the seed pods turn black in the middle, the edge is yellow, and the bracts are yellowish-green, it's time to harvest the hollyhock seeds. Hollyhock seeds weigh about 9.2 grams every 1,000 thousand seeds, which can be used for 9 years if being storage well.
Harvesting hollyhock seeds is relatively simple. Wait for the hollyhock seed to become totally ripe and the pods to dry, then simply snap the pods off the stalks and take the seed out into a black bag or suitable container for storage. (If you want to plant the seed immediately instead of saving it, please read next: How to Grow Hollyhock from Seed). One seed pod contains a lot of seeds while you may don’t need such a huge number of seeds, so you can choose the best available hollyhock plants to harvest the seeds.
Pay attention: Hollyhock stalks and seed pods may irritate your skin, so it is better to wear sleeves and gloves when harvesting hollyhock seeds.
Before being stored in a cool dark and dry place, the seeds need to be stirred every day with a finger. This will help you to dry the seeds evenly and completely, and to redistribute them. The well-stored seeds can be used for 9 years.