Onions are easy to grow—and an essential ingredient in so many recipes. Want onions in a hurry? Start with plants and you'll harvest bulbs just 3 ½ months after planting. Many gardeners also like onion sets for their ease of planting and quick results. You can also start onions from seed. Most gardeners start onion seeds indoors and transplant them when the weather warms in spring. When selecting onions, remember that "long day" type onions, which need 13-16 hours of daylight, do best in the Northern zones; "short day" types do best in the Southern zones and thrive in regions with a mild winter climate. "Day-neutral" types are grow well in most zones.