Are Red Onions Easy To Grow: Tips On Growing Red Onions

Two Whole Red Onions
red onions
(Image credit: Gardening Know How, via Nikki Tilley)

Eighty-seven percent of the onion varieties used in cooking are culled from the common yellow onion. While there are many varieties of yellow onion, its less utilized cousin, the red onion, has its place in the kitchen for its mild, sweet flavor and brilliant color. So, are red onions easy to grow? When is planting and harvesting time for red onions? Read on to learn more.

Are Red Onions Easy to Grow?

Growing red onions is as easy as any other type of onion. All onions are biennials, meaning they take two years to complete their life cycle. In the first year the seed grows, forming modified leaves and tiny underground bulbs. In the succeeding year, red onion bulbs mature until they're ready to harvest. Most gardeners plant onion sets the second year that small red onion bulbs to hasten the maturation and harvest of the onions.

Planting and Harvesting Red Onions

With regards to white vs. red onions, there's no difference when growing red onions as opposed to growing onions in general. There is a difference in flavor with white onions milder than red and having a shorter storage life than red onions. Both types of onion come in a multitude of varieties with varying planting times, thus different harvesting times.

How to Grow Red Onions

To get onions off to a good start, mix an organic or time-release fertilizer into the soil prior to planting. Make sure the fertilizer is beneath the planting furrow. This is called “banding” and makes sure the nutrients are exactly where the young onion roots can find them. Mix a 2 inch (5 cm.) layer of compost into the soil before adding the fertilizer. All onions need plenty of sun and well-draining soil with a pH between 6.0 and 6.8. Set the onion bulbs 1 to 2 inches (2.5-5 cm.) deep so the roots are well covered but the neck isn't set too deeply. Space the plants 6 inches (15 cm.) apart in furrows 12 inches (31 cm.) apart. Water the onions until they are wet, but not drenched. Onion roots are shallow, so they need a consistent supply of water, which will also garner sweeter onions. You can lay a light layer of grass clippings or other fine mulch around the onions, but be sure to keep it away from the onion tops which need full access to the sun.

When to Harvest Red Onions

Okay, so you have patiently waited throughout the summer and are itching to dig up the red onions and try them. The question is, when is the right time to harvest red onions? You can pull onions after a few weeks if you just want to use them as scallions, but for full sized onions, you must be patient and let them mature. Onions are ready to harvest when the bulbs are large and the green tops begin to yellow and fall over. Stop watering the onion when around ten percent of the tops begin to fall over. You can now harvest the onions or leave them in the ground to be stored and used as needed. To harvest the onions, dig the onions up and shake off the loose soil. Lay them out to cure with the tops still attached, in a warm, airy place. Keep the onions dry with good air circulation so they don’t rot. As the onions cure, the roots shrivel and the necks dry out. Allow the onions to cure for seven to ten days and then either braid the tops for storage or remove the tops and roots with pruning shears. Store the cured onions in a cool, dry place between 35 and 50 degrees F. (1-10 C.).

Amy Grant

Amy Grant has been gardening for 30 years and writing for 15. A professional chef and caterer, Amy's area of expertise is culinary gardening.