Onions are one of the most popular vegetables in the home garden. They can be grown for green onions and dry bulbs.
Onions are easy to grow. They perform best in well-drained, slightly acidic, fertile soils in full sun. Heavy soils can be improved by incorporating organic matter, such as compost, into the soil. Onions require higher fertility levels than most other vegetables. Before you plant, till in 1 to 2 pounds of an all-purpose garden fertilizer, like 10-10-10, for every 100 square feet. Four to five weeks after planting, sidedress with additional fertilizer. Sprinkle 1 pound of an all-purpose garden fertilizer per 100 feet of row. Spread the fertilizer out in a thin line about 2 to 3 inches from the onion plants’ bases.
An important aspect of onion development is photoperiod or day length. Photoperiod, along with temperature, control bulb formation. The cool temperatures and short days of early spring promote leaf and root growth. Bulb formation begins when a certain day length is reached. When they get 11 or 12 hours of daylight, short-day onion varieties start to form bulbs. Intermediate-day onion varieties need 12 to 14 hours of daylight, and long-day varieties need 14 or more hours of daylight. Long-day varieties are the best choice for gardeners in Iowa and the upper Midwest. Iowans with short days will start to bulb when the plants are small and won’t make big bulbs. Small bulbs can also be expected if long-day varieties are planted in late spring in Iowa.
Onions may be grown from seeds, sets and plants. The planting method selected is based on cost, use, availability and planting ease.
Growing onions from seeds may be the most difficult planting method. However, it is the least expensive. Germination may be sporadic, plant growth is slow, and weeds may be a problem. Plant onion seeds as soon as the ground can be worked in the spring. In southern Iowa, this will be late March or early April, and in the north, it will be mid-April. Plant seeds in rows 12 to 15 inches apart. Cover the seeds with 1/2 to 3/4 inch of soil. When the seedlings are 2 to 4 inches tall, thin the planting. For large, dry onions, plants should be spaced 2 to 3 inches apart after thinning. A full season of growth is needed for mature onions.
Small onion bulbs called sets were grown the previous year, picked, stored over the winter, and then sent to garden centers in early spring. Specific onion varieties are usually not available. They are sold simply as red, white or yellow onion sets. Since the variety is unknown, the flavor, use, and keeping quality of onions grown from sets varies considerably. Before planting sets, divide the bulbs into two groups based on their diameters: those that are less than a nickel and those that are more than a nickel. The larger sets often bolt (produce a flower stalk) and don’t produce good-sized bulbs. Use the larger sets for green onions. The smaller sets can be allowed to develop into mature onions.
Plant sets in early spring as soon as the ground can be worked. Place sets 12 to 15 inches apart in rows that are 1 to 1 1/2 inches deep. For dry onions, plant the sets 2 to 3 inches apart. Sets grown for green onions can be planted closer together.
Plants are onion transplants that are grown in the south of the US during the winter. In early spring, they are shipped to garden centers in groups of fifty to one hundred plants. Onion varieties are available when purchasing plants.
Pick green transplants that are healthy and plant them 12 to 15 inches apart, 1 to 1 1/2 inches deep. To produce large, dry onions, place the plants 2 to 3 inches apart. Plant them as soon as the ground can be worked in spring.
Iowa home gardeners should grow Copra onions (main season, yellow-brown skin, great storage), Candy onions (yellow-brown skin, globe-shaped, short-term storage), Red Burgermaster onions (bright red, globe-shaped, good storage), Sweet Sandwich onions (late season, yellow-brown skin, great storage), and Walla Walla Sweet onions (late season, yellow-brown skin, short-term storage). Category:
Onion sets are one of the easiest ways for home gardeners to grow onions. These dormant onion bulbs can be planted in early spring for a robust harvest of fresh onions by mid-summer. Compared to seeds or transplants, onion sets are quick and convenient. With proper planting and care, they will reward you with an abundant crop.
What are Onion Sets?
Onion sets are essentially miniature or immature onion bulbs that can be planted directly in the garden While seeds take 3-4 months to form bulbs, sets skip that step and get a head start on growth Sets are produced by sowing onion seeds very thickly, which prevents the bulbs from fully maturing. The small underdeveloped bulbs are then harvested, dried and sold as sets.
Onion sets come in a range of varieties – yellow white, and red. Popular types like Stuttgarter and Ebenezer produce nice round onions excellent for fresh eating and cooking. You can also find shallot sets for growing tasty shallots. Sets sold for planting are small – generally under 1 inch wide. Larger sets may bloom rather than form bulbs.
When to Plant Onion Sets
One of the benefits of onion sets is their versatility – they can be planted in either spring or fall in most regions.
For spring planting, sets can go in the ground 4-6 weeks before the last expected frost. The soil needs to be workable and not waterlogged. Avoid planting too early when cold, wet soils could cause the sets to rot. Ideal spring planting times will vary by region and weather.
In fall, onion sets are typically planted 8-10 weeks before the first expected frost so they can form bulbs before winter dormancy. Fall-planted sets will resume growing in early spring.
How to Plant Onion Sets
Planting onion sets correctly is important for good germination and growth. Follow these tips:
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Choose a sunny spot with fertile, well-drained soil. Onions need at least 6 hours of direct sun daily.
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Work plenty of compost into the soil to provide nutrients for the heavy-feeding onions.
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Break up any large clumps in the soil and rake to create a smooth, even bed.
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Make a shallow trench 1-2 inches deep. Space the onion sets 4-5 inches apart in all directions in the bottom of the trench. This allows room for the bulbs to grow larger.
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Place each set into the soil with the pointed end up. The tip should be just above or barely covered by the soil surface. Push it in firmly enough that just the bottom half is buried.
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Cover the sets gently with soil and water well. The soil should be kept evenly moist but not waterlogged.
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Apply a balanced organic fertilizer or one specifically formulated for onions after plants start growing.
Growing and Harvesting Onion Sets
Once planted, onion sets will start sending up green shoots within 1-2 weeks. Over-fertilizing with nitrogen early on can cause excessive leaf growth and poor bulbing. Wait until plants are 4-6 inches tall and then side dress with fertilizer every 2-3 weeks.
Onions have shallow roots and compete poorly with weeds. Maintain a weed-free area around the plants by hand pulling or hoeing carefully to avoid damage. Side dressings of fertilizer can double as a way to bury small weed seedlings.
Stop fertilizing when the onion tops start falling over, which signals maturity. This will typically happen 3-4 months after planting sets. Avoid excessive watering at this stage to speed up ripening.
When about half of the tops are down, push or gently twist over any remaining upright leaves. Allow onions to cure outdoors for 1-2 weeks until skins are papery. Store cured bulbs in a cool, dry spot with good air circulation to last for months.
Tips for Growing Great Onion Sets
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For milder onions, plant yellow or white sets. Red onions have the strongest flavor.
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Larger sets may bolt and produce flowers rather than big bulbs. Choose smaller sets under 1 inch wide.
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Rotate planting sites each year to avoid disease buildup in the soil.
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Separate sets by variety when planting to avoid cross-pollination that can cause odd shapes or flavors.
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Harvest onions promptly once mature and cure them well for longest storage life.
The Benefits of Planting Onion Sets
Onion sets offer gardeners several advantages:
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Sets eliminate the need to start seeds indoors. Just plant and grow!
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Earlier harvest compared to seeds – bulbs size up faster.
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Less tedious thinning required versus crowded seedling stands.
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Wider planting window in spring and fall.
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Excellent for successive plantings to extend the harvest.
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Produce well even in poorer soil conditions.
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Provide bigger yields in smaller garden spaces.
For a streamlined approach to growing onions, it’s hard to beat the ease and reliability of planting onion sets. With minimal effort, you can fill your kitchen with an abundance of sweet, juicy onions.
Planting Onion Sets: What to Watch Out For
FAQ
What kind of onions to plant in spring?
What is the best month to plant spring onions?
How do you store onion sets for spring planting?
Can you plant onions in spring?
Sharing is caring! Here in the UK, we typically grow onions from either seeds or sets, with sets being the easier choice. And while seeds must be started early in the year, sets can be planted throughout spring. So with that in mind, let me show you exactly how I plant my onion sets in springtime!
How do you plant onions in a garden?
Generally onion sets are planted 1-2 inches deep. Plant each bulb with the roots down and pointy side up. Space the onions 4-6 inches apart with rows spaced 10-15 inches apart. Cover them back up with soil and then water so the soil is moist. Thoroughly mulch with shredded leaves or straw. The mulch will help protect the plants.
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 onion seeds?
In spring, plant onion sets outdoors as soon as the ground can be worked, usually in late March or April, when temperatures are no longer likely to dip below 28°F (-2°C). In spring, start onion seeds indoors for about 6 weeks before transplanting to the ground (once the soil is at least 50°F).