Start seed indoors 6-8 weeks before transplanting into the garden. Optimum soil temperature for seed germination is 65-80 degrees. Transplant to the garden about 2-4 weeks before your average last frost. If seedlings begin to tip over, trim tops to 3". Green onions can be direct sown in the garden from early spring to mid-summer. The length of summer days provides a trigger for onions to grow bulbs. There are onions that bulb best where summer days are short (low latitudes), intermediate (medium latitudes), or long (high latitudes).