how to plant autumn onion sets

How to Plant Autumn Onion Sets for a Bountiful Spring Harvest

Onions are a versatile vegetable that adds flavor to many savory dishes. While onions can be grown from seeds sown in spring planting onion sets in autumn offers several advantages. Onion sets are miniature onion bulbs that allow you to get a head start on next year’s onion crop. Follow this complete guide to learn when and how to plant autumn onion sets for big healthy bulbs come spring.

What are Onion Sets?

Onion sets are essentially baby onion bulbs. They are grown specifically for autumn planting rather than consumption. Onion sets form petite bulbs just 1/2 to 1 inch wide, compared to a mature onion bulb which can grow to over 4 inches across.

These tiny bulbs are planted out in fall and overwinter in the garden. Then they develop into full size onions the following spring and summer. Each planted set yields one large onion bulb at maturity.

Reasons to Plant Onion Sets in Fall

Growing onions from sets planted in autumn offers several advantages over sowing seeds in spring:

• Earlier harvest – Sets get a head start in fall so you harvest bigger bulbs weeks earlier next year

• Less bolting – Cool weather reduces risk of premature flowering (bolting)

• Less weed competition – Onion sets get established before spring weeds germinate

• Wider variety – Sets allow growing specialty varieties not available as seeds

• Higher success rate – Sets are less prone to soil-borne diseases than onion seeds

For northern gardeners, onion sets bridge the gap between fall and spring planting seasons.

When to Plant Onion Sets

Onion sets should be planted in the garden 6-8 weeks before the ground freezes in winter. This timing varies by growing zone, but generally falls between late September and late November.

• Zones 3-4: Late September to mid October

• Zones 5-6: Mid October to early November

• Zones 7-8: Early to late November

Ideally, plant sets when daytime highs are 60-70°F and night temps are averaging 45-55°F. Avoid planting too late when ground may freeze.

Selecting Onion Set Varieties

Onion sets come in a rainbow of bulb colors including yellow, white, and red. Popular varieties include:

• Yellow – Copra, Stuttgarter

• White – Evergreen White Bunching, Walla Walla

• Red – Red Wethersfield, Red Burgundy

Choose early maturing, long day varieties adapted to your region. Talk to local gardeners or your local extension office for the best performer sets in your area.

Where to Buy Onion Sets

Look for onion sets bundled in mesh bags at local garden centers in fall. Most sets are a variety called Stuttgarter. Specialty catalogs and online seed shops offer a wider selection.

When buying sets, look for:

• Firm, compact bulbs without mold, shriveling, or sprouting

• Similar bulb size in a package for even growth

• Correct variety and quantity for planned planting

Avoid sets with green sprouts as they may bolt before forming bulbs.

How to Plant Onion Sets in Fall

To get your autumn planted onion sets off to the best start, follow these simple planting steps:

Site Selection

Choose a planting area with full sun in fertile, well-draining soil. Avoid heavy clay or areas prone to standing water.

Soil Preparation

Work aged compost or well-rotted manure into the top 6 inches of soil to enrich and loosen the earth. Rake smooth.

Make Furrows

Use a hoe to create 2-3 inch deep furrows spaced 9-12 inches apart across the planting area. Wider rows give onions room to grow.

Set Bulbs

Place onion sets into furrows 4-6 inches apart, pointed end up. Push sets gently into soil so just the tip shows. Cover sets with surrounding soil.

Water & Mulch

Water furrows after planting. Add a 2 inch layer of straw or shredded leaves to conserve moisture and insulate bulbs.

Proper autumn planting sets your onions up for vigorous root growth before winter dormancy.

Growing Onions Sets Through Winter

Onion sets require little care once planted in fall. Here are tips for success:

• Water plants if autumn turns dry to establish roots before winter

• Mulch over sets with straw or leaves after soil freezes to insulate bulbs from temperature swings

• Check that mulch remains in place throughout winter

• Avoid walking on planted areas or working soil when ground is frozen

• Remove mulch in early spring so plants can emerge as weather warms

The small bulbs remain dormant through winter. Onion sets resume growing when soil temperatures rise above 40°F in spring.

Onion Care in Spring

As soon as soil thaws in early spring, begin caring for actively growing plants:

• Pull back any remaining winter mulch

• Weed around onion plants while young to minimize competition

• Side dress each row with balanced organic fertilizer

• Water weekly if rainfall is lacking, avoiding waterlogged soil

• Monitor for insect pests and disease; treat organically if found

• Hill soil around the base as bulbs enlarge to stabilize plants

With proper spring care, onions will be ready to harvest up to 4 weeks earlier than spring sown plants.

When to Harvest Onion Sets

Onions grown from sets are ready to harvest roughly 100-120 days after planting. This means you can harvest bulbs as early as May or June, depending on your climate.

Plants are mature when the tops begin to fall over and brown. Stop watering at this point to hasten ripening. Then pull up bulbs and allow them to cure in a warm, dry spot for 1-2 weeks. Trim tops and store cured onions in a cool pantry or cellar. Autumn planted onions store beautifully all the way until the next year’s crop comes in!

Storing and Saving Onion Sets

Cured bulbs keep for months in a cool, dark location. Check stored onions periodically and use up any that show signs of sprouting or spoilage. Saving your own onion sets is also an option:

• Select your largest, healthiest bulbs from this year’s harvest

• Remove the outer papery layers and stalks

• Allow bulbs to cure for another 2 weeks

• Place cured bulbs in an open container in a cool (40-50°F), dry location

Sets will keep for 6-10 months; discard any that show signs of rot. Replant best bulbs the following autumn.

With proper curing and storage, you can perpetuate your own onion sets season after season.

Troubleshooting Onion Sets

Onion sets are quite hardy but occasionally issues may arise:

• Flower stalk forms before bulb matures = Bolting, caused by cold weather or small sets. Remove flower stalk to redirect energy to bulb growth.

• Plants fall over early in season = Sets planted too shallowly. Hill up soil 1-2 inches around bulbs to stabilize.

• Stunted, pale plants = Nutrient deficiency from unamended soil. Side dress with balanced organic fertilizer.

• Distorted or rotten bulbs = Disease like basal rot. Avoid planting sets in same soil year after year.

• Holes in leaves = Onion thrips. Spray with insecticidal soap.

With care, you can achieve a bountiful onion set harvest!

Enjoying the Benefits of Onion Sets

Growing onions from autumn planted sets offers many advantages to the home gardener:

• Earlier harvest extends enjoyment of fresh onions

• Wider variety allows growing specialty onions not sold as seeds

• Sets adapt well to a wide range of climates

• Compact bulbs efficiently use limited garden space

• Reduced weed and disease pressure improves success

• Saving your own sets perpetuates the annual harvest

With proper timing and care, onion sets yield delicious, long-storing bulbs from an easy fall planting. Give this homesteading classic a try – you may find planting onion sets in autumn becomes a yearly tradition!