Plant red onions in a well-lit location. The soil should be well-drained, and its pH level should be about 6.0 to 6.8. Place the onion bulbs 1 to 2 inches deep in the soil; don't insert the top part of the bulb too deeply. Plant onion bulbs 6 inches apart in furrows that are 12 inches apart. Water the onions after planting, and continue watering them frequently throughout the entire growth period.Continue Reading
Before planting the onions, dig up some of the soil from the planting location, and add some fertilizer and a 2-inch layer of compost to the soil. Mix everything well, and place the soil mixture underneath the onion bulbs. You can use both organic and time-release fertilizer for this purpose. Since onions like the soil moist, place a layer of mulch, such as grass clippings, on the ground around the onions, but don't cover the green parts of the onions with it.
You can harvest onions as early as several weeks after planting if you want to use them as scallions. Once the green leaves on the onions start to turn yellow, the onions are mature and ready to harvest. Harvest the onions, or store them in the ground until you need them.Learn more about Outdoor Plants & Flowers