Onions are a cool-season crop and tolerate moderate freezes but when cold snaps arrive cover beds if temperatures will reach. Seeds can be direct sown or started indoors 8-12 weeks before the last. When Is The Best Time To Plant Onions Growfully To grow onions from seed you can either start seeds indoors sow seeds directly outside or use the winter sowing. . Onions can be started from seeds or from sets small bulbs. We Have A Huge Inventory of Over 1300 Varieties Of Seeds Including Many Heirlooms. Web HOW TO GROW ONIONS FROM SEED. They can tolerate light frosts and you can plant them when temperatures reach 50 F. You can also raise your own transplants by. Fall seeded crops are susceptible to bolting the following spring if. Ad Your Source for Seeds and Supplies. The ideal month to plant onion seeds varies based on where you live. Web Harden off seedlings then plant them in the garden. In c...