Onion sets are a great way to get a head start on growing onions in spring. Compared to planting onion seeds or transplants, sets allow you to harvest full-size onions much earlier in the summer. This comprehensive guide will teach you everything you need to know about using onion sets for spring planting.
What are Onion Sets?
Onion sets are miniature onion bulbs that have been grown from seed the previous year. They are harvested when they reach a small 1/2 to 3/4 inch size and “cured” over winter for planting the following spring.
Sets give gardeners a huge advantage over sowing seeds directly because they have a year head start on growth. This means you can produce full-size bulbs in just 60-80 days after planting. Onion seeds, on the other hand, take up to 150 days to reach maturity.
Benefits of Using Sets for Spring Planting
There are several key advantages to using onion sets instead of seeds or transplants:
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Faster maturity – Sets bulb up quicker, allowing you to harvest ripe onions much earlier. Great for impatient gardeners!
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Higher yields – More sets will successfully grow into large bulbs compared to delicate seedlings.
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Fewer weeds – Sets pop out of the ground fast, out-competing weed seeds. Easier to spot and remove weeds.
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Less maintenance – Thinning and weeding is simpler since sets are bigger than sprouts
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Bigger bulbs – Onions grown from sets tend to be more uniformly sized and larger.
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More reliable – Germination rates are higher and more consistent than sowing seeds.
When to Plant Onion Sets
Timing is important when it comes to planting onion sets. They need to be planted 4-6 weeks before the last expected frost in your area. This gives them enough time to establish roots before cold weather arrives.
Planting too early while soil is still frozen risks the sets rotting. Planting too late doesn’t allow bulbs enough time to size up. Check your local frost dates and plant accordingly.
In most regions, sets should be planted in March or April. In warmer climates, February or early March planting is suitable.
Selecting the Best Onion Set Varieties
Onion sets come in a few different types – yellow, white, and red. Each imparts subtly different flavors:
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Yellow – The most common. Mild, well-balanced flavor. Excellent multi-purpose onions.
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White – Very crisp texture with a strong, pungent taste. Great for salsa.
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Red – Beautiful color. Flavor is moderately spicy when raw. Better used fresh vs. cooked.
For spring planting, choose smaller sets about the size of a nickel. Overly large sets may bolt before bulbing. Look for plump, firm sets without mushy spots or signs of sprouting.
How to Plant Onion Sets
To plant, first prepare soil by mixing in 1-2 inches of compost. Onions prefer loose, fertile soil with good drainage. Create planting rows or patches.
Push sets 1-2 inches deep into soil, pointy end up. Space 2-4 inches apart depending on desired bulb size. Closer = smaller onions.
Cover sets with a thin layer of soil or mulch. Water gently. As sprouts emerge, add more mulch up to 3 inches deep to conserve moisture and deter weeds.
Onion Set Spacing Guide
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Small spring onions – space 1 inch apart.
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Medium bulbs – space 2-3 inches apart.
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Max size bulbs – space 3-4 inches apart.
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Allow more room for large, sweet onion varieties.
Caring for Onion Sets
Onion sets are one of the easiest crops to grow. Here are a few tips for success:
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Weed early and often – Sets can’t compete with established weeds. Stay on top of weeding.
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Water regularly – About 1 inch of water per week. Allow soil to dry slightly between waterings.
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Use mulch – Conserve moisture and block weeds. Replenish as needed.
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Avoid excess nitrogen – Too much nitrogen causes rapid, weak foliage growth and small bulbs.
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Watch for pests – Onion flies and thrips can damage leaves. Remove affected foliage promptly.
Harvesting Onion Sets
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Bunching onions – Harvest green onions anytime after 6 weeks when stalks are 6 inches tall. Simply pull up and use fresh.
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Bulb onions – Allow tops to flop over and turn brown before harvesting bulbs. This signals maturity. Carefully dig bulbs and allow to cure for 1-2 weeks protected from sun before storing.
Enjoy an abundant onion harvest this summer by planting hardy onion sets this spring!
Growing and care of onions
- Onions are often grouped according to taste (mild and strong-flavored), color (white, yellow, and red), and use (storage or freshly eaten). Globe varieties tend to keep longer in storage.
- Onion cultivars also have different requirements as to the number of hours of daylight required to make a bulb. If the seed catalog lists the variety as long day, it sets bulbs when it receives 15 – 16 hours of daylight and is adapted to Northern summers. Short-day varieties set bulbs with about 12 hours of daylight and are used in the deep South for winter production. There are also “intermediate” cultivars. Mid-Atlantic gardeners can experiment with all groups, although long day and intermediate types will probably perform best.
- Do not hill up the soil on onions, as this encourages stem rot. Bulbs emerge above the soil as they enlarge.
- Watering – Ensure ample moisture, especially after bulbs begin enlarging. Onion bulb size is directly proportional to the amount of water applied to the onions during the growing season.
- Weeding – Onions compete poorly with weeds because of shallow root systems. Hand-pulling weeds or shallow cultivation is necessary; do not hill up the soil on onions. Maintain a weed-free bed and apply an organic mulch to maintain soil moisture.
Planting Onion Sets: What to Watch Out For
FAQ
Can you plant onion sets in spring?
Onion sets can be planted out directly into your garden in march or april when the weather will be more mild and less wet (this will differ from region to region obviously). If you are in no hurry and don’t want an early harvest of onions, you can choose to just wait and plant them directly outdoors.
What is the best month to plant spring onions?
Spring onions are easy to grow from seed and will grow in any fertile, well-drained soil, in full sun. For a continual harvest of spring onions in summer, sow at three-week intervals from September to February. To grow spring onions indoors over winter, sow in March and harvest in spring.
What is the best time to plant onion sets?
The best time to sow onion sets is mid March to mid April. If you are sowing red onion sets is better to leave them till April as they are more prone to bolting and a later planting may help. Sets can also be sown in Autumn from September to early October.
Is it too late to plant onions in May?
Onions are one of the first crops planted in the spring. They are the first in our greenhouses in March and the first in the fields in April or early May.
Should you plant onion sets this spring?
If you want to have a great harvest this summer of sizable onions – then one thing is for sure, you need to plant onion sets this spring instead of seeds or transplants! Onions can be planted and grown using three different planting methods. The first is by planting seeds. The second is to plant small seedlings, often called transplants.
How do you plant onions?
There almost seems to be an endless string of ways to plant and grow them. You can plant onions with bulbs (sets), transplants or by seed. Adding to the confusion is knowing when to plant them. In some climates, it’s best to only plant onions in the spring. For other areas, they can be planted in the spring or fall.
How to grow onion sets?
Here is a brief guide on how to grow onion sets: Step 1: Choose a sunny spot with well-drained soil rich in organic matter. Step 2: Sow your seeds densely to promote smaller bulb growth, lightly covering them with 1/4-1/2 inch of soil. Step 3: Let the seeds germinate without thinning the onion seedlings.
How far apart should you plant spring onions?
This space is vital to let spring planted onion sets have room to grow. If you are, however, looking to grow spring onions from your sets (green onions), plant bulbs closer at 3/4″ apart. You can harvest green onions in as little as 4 weeks. They simply don’t need or require additional space in the row.
Are onion sets good for spring bulbs?
So that leaves onion sets – which just happen to be the perfect answer for fast growing spring bulbs! Onion sets are onion seeds that have been sprouted and allowed to grow to a small onion. They are then harvested and allowed to go dormant. But when you plant the bulb back into the soil in the spring, it returns to life to grow once again.
When should you plant onions in a garden?
Also Read: Ep 10 – Soil vs Dirt: Know the Difference to Prepare your Garden Onion sets can be planted in late winter/early spring planting for summer harvest or late summer/fall planting to harvest onions the following spring. (If you are planting in fall, make sure to cover with mulch or grass clipping to protect your onions from hard freeze).