Choose a spot in your yard or garden that gets full sun and has soil that drains well. Till the dirt to a depth of 12 inches and work in compost, blood meal or another organic material to enrich the soil with nutrients. This will ensure that the green onions grow strong and healthy, and continue to produce shoots throughout the growing season.

As soon as the soil is workable, about four weeks before the last frost, it's time to plant the seeds or sets you have ready. If you have seeds, sow them thickly about 1/2-inch-deep in rows spaced 1 foot apart. Water the garden bed thoroughly. The onion seeds will germinate when the soil is anywhere between 65 to 86 degrees Fahrenheit (18.33 to 30 degrees Celsius). It may take up to a month for onion seeds to germinate.

If you live in a cold climate with a late spring, you can start the seeds indoors about eight weeks before the last frost. Plant the seeds in peat seed starter pots and keep them well-watered. Put them in a warm, sunny room to during the germination period. When the ground outside is warm enough to work with, transplant the seedlings to the garden or a larger pot.

When the first green shoots begin poking up, determine whether to thin them to give them each a bit more room. Green onions grow well in bunches, but for best results the mature plants should be spaced 2 to 3 inches apart.

Green onions need evenly moist soil throughout the growing season. Provide the onion plants with about 1 inch of water per week. For optimal plant growth, the soil does not need to be soggy, but it should be moist. Water the garden bed every few days, or when it begins to look dry and dusty.

After three to four weeks, the green shoots will be 6 to 8 inches long and ready to eat. Harvest them by pulling the entire plant from the ground. The plant will not yet have formed a bulb. Both the white and green parts of the onion are flavorful. 

If you only want to use the green part of the onions, and not the white part close to the roots, you can use a pair of scissors to simply cut off the green tops. Leave an inch or two of growth. The onions will continue to grow, and you can harvest the greens again once they're 6 to 8 inches long. Note that they will become stronger-tasting as the plant matures.

Onion, Allium cepa
Pollination, insect; Life Cycle, biennial; Isolation Distance, 1 mile
Onions are an insect pollinated biennial, and can be a challenge to keep pure. Keeping flowers covered and hand pollinating with a paintbrush is often the safe way to go. Allow seeds to ripen and dry on the plants, then harvest quickly to avoid losing seeds. Further drying in a paper bag will probably be necessary before separating seeds from the flowers. Flowers will likely need to be staked as they will become heavy with seeds.