I planted about six hundred seedlings of two onion varieties in mid January. With our warmer weather of the last ten days, they are growing quickly. I noticed this morning a few of them have already started bolting. They have small flower heads forming. The bulbs are just beginning to form above ground and they shouldn't be ready to start harvesting for another four to six weeks. What is causing the early bolting? What will be the effect on the bulb of the flower set? Any ideas on how to retard bolting? Should I leave the plants that bolt early in the ground for continued growth?