Could you tell me how to grow Allium from seed?
I will assume you are propagating ornamental Allium. According to the American Horticultural Society’s Plant Propagation (edited by Alan Toogood; DK Publishing, 1999), Allium seeds may be sown any time from late summer to early spring. Seeds should be collected when the flower heads turn brown and before the seedpods open. If you tug gently on the flower stalk and it comes away easily from the base, the seed is ripe. Cover the spot where the stalk was removed with soil to prevent entry to pests. With smaller flowering Allium, you can shake seeds directly into a paper bag (without removing stalks). Sow the seeds fresh, or store them at 41 degrees F, and sow in the spring. Germination time is usually 12 weeks, but in some cases it will take up to a year.
The Royal Horticultural Society says that Allium cultivars may not come true from seed, so you may want to consider alternate methods of propagation, such as by offsets or aerial bulbils.