Many recipes use a wide assortment of onions, but red onions are popular for culinary dishes. These onions are favored for their mild yet sweet flavor and gorgeous reddish-purple color. Far too many gardeners shy away from learning how to plant red onions, though.
Planting red onions isn’t as hard as you’d think it is, especially when growing red onions from seed. In their first year of life, the seed starts to form into a tiny bulb. By the second year, the bulbs mature, and you have a large crop of onions ready for long-term storage.
Red onions are as easy as growing yellow onions or sweet onions. While many onion varieties are a little overwhelming, they each have a unique flavor that gives a dish something special.
Things to Know before Planting Red Onions
Green onions, scallions, and chives are better for garnishing. Leeks, shallots, and Walla Walla onions are better when cooked into a dish. You don’t have to grow all of the different types of onions to have a diverse garden. Instead, choosing to plant onions from one or two cultivars is more than enough.
Finding the best way to plant red onions depends on how much work you’re willing to do. Planting red onion bulbs is going to be slightly different than planting seeds or transplanting seedlings.
Red onions are biennial plants called Allium cepa, and they belong to the same family as garlic, shallots, leeks, and onions. Regardless of the variety, onion bulbs will not form without an appropriate day length.
Long-day onions require at least 14 hours of sunlight for proper germination and bulb formation. Short-day onions require at least 12 hours.
There are also three different methods that most gardeners use for planting onion crops. You may choose to plant onion sets, seeds, or transplants. Onion seedlings are harder to grow as transplants because of their shallow and sensitive root system.
Onion seeds are simple to grow but take longer to mature during the growing season. Keep reading to find out tips for when to plant red onions and different gardening strategies for these bountiful plants.
Tips for How to Plant Red Onions
Whether you’re growing red onions from seed, sets, or transplants, there are a few keys to success that will help you have some of the healthiest onion tops and bulbs this summer.
What Month do You Plant Red Onions?
The best time to plant red onions is anytime in early spring or early fall. How long it takes for a small onion to mature could take a while, though.
This delay is because planting times depend on the way you plant them. Your hardiness zone also plays a role in when you plant them. In general, you’ll be able to harvest red onions when summer is over and the stalks begin to droop.
For even more success, learn what to plant next to red onions. Companion planting has many garden benefits.
Growing Red Onions from Seed
Growing red onions from seed definitely takes the longest, yet it is one of the easiest ways to grow these crops. Start by planting red onion seeds directly outdoors. The tiny seeds cannot withstand the harsher temperatures from winter, so make sure the soil is around 45°F before sowing them.
If you want to sow them early, grab a small container and fill it with rich potting soil roughly six weeks before the last frost of the winter. The proper space when planting red onions from seed is to place the seeds one centimeter apart from each other and cover them with rich soil that has been amended with organic matter.
Keep the soil damp and moist and ensure that they get direct sunlight in their chosen location. Full sun means a minimum of 6 hours of sunshine every day. Continue to water them several times per week.
Those that start their seeds in a container should start transplanting seedlings about six to eight weeks after your onions start to sprout. They are typically around one or two inches tall at this point. However, growing onions in pots is fine. Ensure they get enough sun and water to thrive.
How to Plant Onion Seedlings
Your local nursery is almost guaranteed to carry a few selections of onion seedlings. This local selection of different types of red onions is more convenient if you don’t want to start seeds.
Prepare the soil by adding nutrient-dense matter that helps the bulbs grow more prominent and flavorful. The planting depth for onions is in one-inch holes in the beds. Gently transfer the seedlings into each one. Cover the area with extra soil and care for them as usual.
Planting Onion Sets
Onion sets come from the previous years’ crops and are the preferred way to grow red onions. Find a location with plenty of sun and a soil pH between 6.0 and 7.0.
Dig furrows that are two inches deep and 12 inches apart. Place the sets in the furrow and keep the spacing about six inches apart from each onion set. Cover them with soil and water the area thoroughly.
Planting red onions in containers or raised beds isn’t all that different from growing them in an outdoor bed and is usually easier because you have more control over environmental factors and soil diseases. People also feel that growing them in containers makes it easier to get rid of pests like thrips and onion maggots.
Plant red onions in their designated containers the same as you would plant them outdoors. Ensure that they are in an area with plenty of sunlight. Spread mulch around the beds to keep the soil warm and free from weeds.
Harvesting, Storing, and Cooking Red Onions
Once you’ve patiently waited until the end of summer, it is time to harvest red onion plants. When are onions ready to pick? These onions are ready for harvesting when the bulbs are large and their green tops start to yellow and fall over.
Pull at the top of the onion bulb to remove it from the ground. Remove the excess dirt and allow it to cure in a dry place for about one month before you cook with it. The outer layers of the onions should be papery.
Store uncut red onions in the pantry or slice or chop them and freeze them for later use.
One of our favorite ways to use these onions is to turn them into pickles and use them as a fresh garnish or stir them into guacamole. Note that when talking about red vs white onion, their flavors differ, although you can substitute one for another in most dishes.
Heat the vinegar, water, salt, and sugar in a pan over medium-high heat. Once the mixture simmers, peel and cut the red onion into slices. Place the slices in a clean glass jar and pour the hot vinegar liquid over the top.
Screw the lid onto the container and allow the onions to marinate in the fridge for at least 30 minutes before eating.
There is something magical about red onions. Their vibrant colors, large shapes, and sweet taste are things that most of us can’t get enough of. These planting-red-onions tips for at-home gardening are a simple way to add more nutrition to your diet in the most flavorful way possible.
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