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Red onions (Allium cepa) are biennial bulbs grown as edible plants worldwide.
Onion plants have long, hollow green leaves that emerge from an underground stem with shallow roots.
Red onions are related toyellow onions,garlic,leeks, chives, and shallots.
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Onion plants are toxic to pets,so keep that in mind when growing them indoors or outdoors.
Choose sets smaller than three-quarters of an inch around to avoid woody stems.
you might also plant red onions in the fall and overwinter them until spring.
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If you have poorly drained clay soils, grow red onions in raised beds or containers.
you’re free to plant them closer together to harvest young plants asgreen onions.
Plant seeds three-quarters of an inch deep.
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Then, space transplants about four inches apart in rows 12 to 18 inches apart.
Red Onion Plant Care
Light
Red onions need as much sunlight as possible.
Your plants should receive a minimum of six to eight hours of full sun each day.
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Soil
Onions grow best in loose soil with good drainage and lots of organic matter.
The ideal soil pH for red onions is between 6.0 and 7.0.
Water
Red onions require at least one inch of water each week.
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Check the soil moisture with a trowel and add more water as needed.
Sandy soil may need more frequent watering.
Stop watering when the onion leaves start to fall over.
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Hard freezes below 20 degrees F. can damage plants.
Watering well before a hard freeze and protecting plants with mulch can help insulate them from damage.
Fertilizer
Prepare the planting site by adding organic compost in fall or spring.
Starting a few weeks after planting, apply a nitrogen-rich organic fertilizer every two weeks.
As the bulbs grow, they push against the surrounding soil creating cracks in the surface.
This is a sign to stop fertilizing.
Pollination
Red onions are not self-fertile, so they rely on beneficial insects to pollinate.
They grow in clusters rather than single bulbs.
Harvesting Red Onions
Stop watering red onions when leafy tops begin to fall over.
Thye areready to harvestone to two weeks later, when the stem has dried out.
Since containers tend to dry out more quickly in hot weather, you may need to water more frequently.
This is thought to promote stronger roots, more vigorous plants, and bigger bulbs.
Planting onion sets in the spring rather than growing plants from seed will give you an earlier crop.
Red onions planted from seed tend to have a better success rate, too.
Here’s how to propagate your own red onion sets.
How to Grow Red Onions From Seed
Red onion seeds are best direct sowed.
Though you could attempt to grow and transplant seedlings into your garden, the best method is direct sowing.
Cover the seeds with a light layer of soil.
Onions require an open and sunny growing site, fertile soil, and good drainage.
Red onion sets should be planted as soon as the ground can be worked in early spring.
Red onion seeds should be started indoors eight to ten weeks before your region’s last frost date.
Red onions can also be planted in fall four to six weeks before your first frost date.
