Most farmers in the United States have reported commendable success in growing green and dry bulb onions. However, some home growers have reported that about 20% of the planted onions never grow a bulb, while the rest of the crop produces tennis ball-size bulbs.
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From the wrong choice of varieties to grow to poor care for the crops, growing onions at home is associated with dozens of challenges, which explains why some find the venture unworthy.
The good news is onion home growers realize success with experts’ resolution of the challenges, recommendations from key agricultural bodies and onion-growing best practices.
For instance, the National Institute of Food and Agriculture revealed that managing onion crop pests and diseases can lead to an annual increase of $13 million in crop value, recommending effective pest elimination strategies and pest-tolerant onion varieties.
So how do you grow onions at home? There are simple ways to grow onions indoors for sustainable home use supply throughout the year.
In this article, we guide you through growing onions from seeds and store-bought onions at home. You will also learn how to regrow green onions for multiple harvests, and how to grow onion bulbs outdoors.
For onion prices, please check the prices of onions in the United States
For nutrition, please check this comprehensive breakdown of nutrients in onions
How to grow green onions in containers from seeds
Green onions, also called spring onions or scallions, are the easiest to grow at home as you can grow them indoors in pots or containers.
Here is a step-by-step guide to growing green onion from seeds in a container:
- Add potting soil to a container (about 4 inches deep) and spread it evenly
- Water the soil until evenly moist and let it settle
- Make ¼ inch-depth holes 1-2 inches apart
- Sow 6-8 spring onion seeds in each hole
- Cover the seeds lightly and firm them into place
- Keep the seeds moist in a warm place (15-18 C). Consider placing the pot on a sun-facing window, away from direct sunlight.
- The seeds should begin sprouting in 7 days
How to grow green onions without seeds
If you buy some green onions from the store for your consumption, you can also grow more green onions from them.
Follow these steps to regrow store-bought green onions in water:
- Trim off the fresh green leaves about 2-3 inches from the roots.
- Stick the trimmed green onions in water overnight to rehydrate the roots
- Add some potting soil to a pot
- Water the soil and dig some holes 2 inches apart with the help of your finger.
- Regrow the sprouted green onions in the holes and firm them in place
- Keep the potting mix moist
- New leaves should be growing in three days
Note: You can leave the sprouted green onions in water, and they will regrow to the point of harvesting. However, transplanting them into soil offers more harvests.
Harvesting and regrowing green onions
- Harvest your green onions in 3-4 weeks, and about 6-8 inches tall
- Trim off the fresh green tops, leaving about an inch of green shoots above the soil.
- The trimmed shoots will regrow for another harvest. It’s called the “cut and come again” method
- Alternatively, if you planted your green onions too close, it’s time to thin them
- Pull off as many green onions as you would want to use.
- Thin the rest into other pots/containers such that they are 3-4 inches apart to encourage growth.
How to grow onions from onions
Did you know that you can also regrow bulb onions from store-bought onions? Here’s a step-by-step guide:
1. Preparing the onions
- Get some onions from the store
- Cut off the onions’ bottom quarter (about an inch) from the roots for regrowing. You can use the rest of the onion since we’re only interested in the part capable of growing roots.
- Peel off the outer papery layer since it can be subject to rotting if buried in water.
- Fill as many containers as the number of onions with water. You can use a glass jar or a plastic container.
- Put the onions in the containers, root down in the water, ensuring the bottom part is submerged. Avoid flooding the tops.
- New roots should be growing in 3-5 days
2. Potting the sprouted onions
- Fill one-gallon containers or pots with a potting mix and water until moist.
- Remove as much onion flesh as possible, careful not to damage the emerging roots and shoots.
- Press in the rooted onion slices and cover them with more potting soil until the greenery meets the soil. You want to ensure the onion is situated as if grown from seeds.
- Keep the soil moist as the onion shoots grow
3. Dividing the onion bulbs
- This is best done when the onions have grown small bulbs (about 3-4 months).
- A single onion slice brings forth 2-4 bulbs, each needing space for nutrient uptake.
- Ensure each plant has its own root system established before dividing.
- Dig around the onions carefully until you get them out
- Plant each onion on its own pot
4. Caring for the onions
- It’s time to grow your desired onion bulb
- Keep the onions moist. Water when the soil is about an inch dry
- You can use a 12-4-8 NPK fertilizer for a growth boost for the onions at this point
- Ensure no weeds grow around the point, as they compete for nutrients with the onion.
- You should have ready-to-harvest bulbs in 6-8 weeks.
How to grow onion bulbs from seeds
Onion bulbs do well when planted outdoors. Use these steps:
1. Choosing a location
- Choose a sunny location with well-drained and moist soils
- Add some compost a winter before planting so that it’s not too fresh
- Add a Nitrogen rich liquid fertilizer before planting for a nutrient boost
- Heavy clay soils are ideal for the growth of onions, but planting them on raised beds allows better drainage
- Avoid overly wet conditions, as they may cause the onions to rot
2. Planting the seeds
- Start the seeds indoors in late winter, in a pot. They should sprout in a week and be ready for replanting in 2-3 weeks.
- Make rows about 4 inches apart.
- Plant the seedlings 4-6 inches apart and about 2 inches deep to allow the formation of large-sized onion bulbs.
3. Caring for the seedlings
- Mulch immature bulbs with straw lightly to retain moisture and discourage weed growth. Do not cover emerging bulbs.
- Weed regularly between rows and the onions to avoid competition for resources. Weeding also helps keep pests away.
- Fertilize the seedlings every 3-4 weeks until the bulbs have begun pushing the soils away. The bulbs should emerge above the soil, so let them.
- Too hot or cold conditions soon after planting can cause bolting. It’s particularly advisable that you avoid planting onions outdoors in late spring.
- Water the seedlings regularly during hot summer.
4. Harvesting onion bulbs
- Your onions are ready for harvesting when the leaves are yellow and start to fall.
- Pull the onions off the ground, careful not to bruise them
- Let them dry in a protected space for around two weeks.
How long do onions take to grow
Bulb onions grown from seed take 3-4 months to mature. Green onions are ready to harvest in as soon as 6 weeks if grown from sets (small bulbs) and around 8 weeks when grown from seeds.