If you’re looking to extend your harvest season and enjoy fresh onions earlier than ever, you might be asking what are winter onions. Winter onions are a hardy perennial type, often planted in fall for an early spring harvest. They are a gardener’s secret weapon, offering a reliable crop with minimal fuss.
This guide will explain everything you need to know. We’ll cover their unique benefits, the best varieties to choose, and a simple step-by-step guide to growing them successfully. You’ll learn how to plant, care for, and harvest these versatile alliums.
By the end, you’ll see why they are a valuable addition to any vegetable garden. Let’s get started with the basics.
What Are Winter Onions
Winter onions are not a single specific species, but rather a classification for onion varieties that can survive freezing temperatures and be planted in autumn. Unlike standard bulb onions sown in spring, these are planted as sets or plants in late summer or fall. They establish roots before winter, lie dormant through the cold, and then burst into growth at the first hint of spring warmth.
This growing cycle gives them a significant head start. You can harvest them as green onions very early in spring or let them mature into full-sized bulbs by early to mid-summer, often weeks before spring-planted onions are ready. Their ability to withstand frost and snow makes them exceptionally resilient.
They are typically divided into two main categories: perennial bunching onions (like Egyptian walking onions) and hardy bulbing onion sets specifically bred for overwintering. Both types share the common trait of cold tolerance, providing a continuous supply of onion flavor for your kitchen.
The Key Benefits Of Growing Winter Onions
Why should you dedicate garden space to winter onions? The advantages are numerous and practical for both new and experienced gardeners.
First, they provide the earliest possible harvest. When you’re tired of stored vegetables from last year, the first crisp green tops of winter onions are a welcome sight. You can start cutting greens in late winter or early spring, long before other crops.
Second, they are incredibly low-maintenance. Once planted in the fall, they require very little attention until harvest. They naturally suppress early spring weeds with their vigorous growth and are less susceptible to certain pests that affect later-planted onions.
Finally, they offer excellent yield security. If an unusually wet spring delays your planting, or if a late frost damages other seedlings, your winter onions are already safely in the ground and growing. They represent a reliable food source with minimal input.
Extended Harvest Window
You are not limited to a single harvest day. You can use these onions in stages throughout the growing season.
- Early Spring: Harvest individual plants as pungent green scallions.
- Late Spring: Thin the patch, using the smaller bulbs like pearl onions.
- Early Summer: Harvest the main crop of mature, full-sized bulbs for storage.
- Summer Onwards: Perennial types will produce edible topsets or new shoots for continuous picking.
Popular Varieties Of Winter Onions
Choosing the right variety is crucial for success. Not every onion can survive a hard freeze. Here are some proven, reliable types to look for.
Egyptian Walking Onions (Topsetting Onions)
This is a fascinating perennial variety. It produces clusters of small bulbs (called topsets) at the top of its stalk in mid-summer. The stalk eventually bends over, planting the topsets nearby, which is how the plant “walks” across your garden. You can harvest the underground bulbs, the hollow green stalks, and the topsets for eating or replanting. They are extremely hardy and will come back year after year.
Japanese Bunching Onions (Welsh Onions)
These onions form dense clumps of flavorful green stalks and do not form a large bulb. They are harvested primarily for their green tops, which have a mild, sweet flavor. Varieties like ‘Evergreen Hardy White’ are specifically bred for winter survival and will provide fresh greens from early spring until they bolt in summer heat.
Overwintering Bulb Onion Sets
These are small, dormant onion bulbs sold specifically for fall planting. Popular and reliable varieties include:
- ‘Yellow Senshyu’: A Japanese variety known for its excellent winter hardiness and early summer harvest of semi-flat, yellow-brown bulbs.
- ‘Red Baron’: A stunning red onion that overwinters well, producing deep purple-red bulbs with good storage potential.
- ‘White Star’ or ‘Snowy’: Hardy white varieties that produce firm, round bulbs ideal for fresh use.
It’s essential to source your sets from a reputable supplier who labels them specifically for overwintering, as not all onion sets can handle the cold.
How to Plant Winter Onions Successfully
Timing and proper planting technique are the foundations for a bountiful harvest. Getting this step right ensures the onions establish strong roots before winter dormancy.
Choosing The Right Planting Time
Planting too early or too late can jeopardize your crop. The goal is to plant so that the onions have enough time to develop a robust root system and minimal top growth before the ground freezes solid.
For most temperate climates, the ideal planting window is 4 to 6 weeks before your first hard fall frost. This typically falls between late September and mid-October. Check your local frost dates as a guide. If you plant to early, the onions may put to much energy into leaf growth, which can be damaged by frost.
Preparing Your Garden Bed
Onions thrive in loose, well-draining soil with plenty of nutrients. A poorly drained bed can cause the sets to rot over the winter.
- Select a Sunny Site: Choose a location that receives full sun (at least 6-8 hours daily).
- Loosen the Soil: Work the soil to a depth of 8-12 inches, breaking up any large clumps.
- Amend the Soil: Mix in 2-3 inches of well-rotted compost or aged manure. Onions are moderate feeders and appreciate the organic matter.
- Check pH: Onions prefer a soil pH between 6.0 and 7.0. A simple soil test can confirm this.
- Rake Smooth: Create a level, fine seedbed free of large stones and debris.
Step-by-Step Planting Instructions
Follow these steps for planting onion sets, which is the most common method.
- Separate Sets: Gently separate the small bulb sets from the bundle.
- Planting Depth and Spacing: Plant each set so the tip is just barely visible above the soil surface, about 1 inch deep. Space them 3-4 inches apart within rows, with rows spaced 12-18 inches apart. This gives them room to bulb up in the spring.
- Firm the Soil: Gently press the soil around each set to ensure good soil-to-bulb contact and eliminate air pockets.
- Water Thoroughly: Give the newly planted bed a deep watering to settle the soil and kickstart root growth.
- Apply Mulch: After the ground has begun to cool (usually a few weeks after planting), apply a 2-4 inch layer of straw, shredded leaves, or another loose mulch. This insulates the soil, prevents frost heave, and suppresses weeds. Do not mulch too heavily or too early, as it can create a habitat for rodents.
Caring for Your Winter Onion Crop
Once planted, your winter onions require minimal care until spring. However, a few key tasks will ensure they thrive when growth resumes.
Fall And Winter Care
The main job in fall and winter is simply to monitor the bed. Ensure the mulch remains in place after strong winds. If you have issues with voles or other rodents, you may need to use protective measures like hardware cloth. Other than that, let nature take its course. The onions do not need watering during dormancy.
Spring And Early Summer Maintenance
As temperatures rise and days lengthen, your onions will spring back to life. This is when they need your attention.
Removing Mulch and Weeding
In early spring, once the threat of severe hard frosts has passed, gently pull back the mulch from the emerging green shoots. Leave it between the rows to continue suppressing weeds. Hand-pull any weeds that appear near the onion plants, as onions have shallow roots and don’t compete well.
Watering and Fertilizing
Onions need consistent moisture for proper bulb development. Aim for about 1 inch of water per week, either from rainfall or supplemental watering. Water at the base of the plants to keep foliage dry and prevent disease.
When the plants are about 6 inches tall, feed them with a nitrogen-rich fertilizer, such as blood meal or a balanced organic vegetable fertilizer. This supports the rapid leaf growth that fuels bulb formation. Avoid high-nitrogen feeds later in the season, as they can delay bulbing.
Pest and Disease Management
Winter onions are generally robust, but they can face a few issues.
- Onion Maggots: These pests can be deterred by using floating row covers in spring to prevent the adult fly from laying eggs at the base of plants.
- Thrips: Tiny insects that cause silvery streaks on leaves. Strong sprays of water or insecticidal soap can help manage them.
- Downy Mildew/Pink Root: Ensure good air circulation and crop rotation to prevent fungal diseases. Avoid planting onions in the same spot more than once every three years.
Harvesting and Storing Your Winter Onions
Knowing when and how to harvest is key to enjoying the fruits of your labor. The harvest method depends on how you intend to use the onions.
Harvesting As Green Onions (Scallions)
You can begin harvesting individual plants as green onions as soon as the tops are large enough to use, often in early spring. Simply grasp a plant near the base and pull it from the ground. Use a knife to trim the roots and any damaged outer leaves. This method thins the patch, giving the remaining plants more space to develop into bulbs.
Harvesting Mature Bulbs For Storage
For full-sized, storable bulbs, you must wait for the plants to signal they are ready. In early to mid-summer, the onion tops will begin to turn yellow, flop over, and dry out. This is the plant’s natural process of diverting energy from the leaves to the bulb.
- Stop Watering: Once about half the tops have fallen over, cease watering to allow the bulbs to begin curing in the ground.
- Lift the Bulbs: On a dry, sunny day, gently lift the entire bulbs from the soil using a garden fork. Be careful not to bruise or pierce them.
- Cure the Onions: Lay the bulbs in a single layer in a warm, dry, well-ventilated place out of direct sun for 2-3 weeks. A garage, covered porch, or shed is ideal. The necks should become completely dry and tight, and the outer skins papery.
- Trim and Store: After curing, trim the roots and cut the dried tops back to about 1 inch. Store the bulbs in a cool, dark, dry place with good air circulation, such as in mesh bags or a ventilated crate. Properly cured winter onions can store for several months.
Saving And Replanting Sets
With perennial types or if you save your own sets, you can ensure a never-ending supply. For Egyptian walking onions, simply collect the topsets in late summer and replant them immediately or store them in a cool, dry place for fall planting. For bulbing types, you can save smaller bulbs from your harvest to replant as sets in the fall, though purchased sets are often more reliable for disease resistance.
Common Questions About Winter Onions
Here are answers to some frequently asked questions about growing winter onions.
Can You Plant Any Onion In The Fall?
No, you cannot. Only varieties specifically bred for overwintering have the genetic hardiness to survive freezing temperatures. Planting standard spring onion sets in fall will usually result in the plants rotting or dying during the winter. Always choose varieties labeled for fall planting or overwintering.
What Is The Difference Between Winter Onions And Regular Onions?
The primary difference is planting time and cold tolerance. Regular onions are planted in spring and harvested in late summer. Winter onions are planted in fall, survive the winter, and are harvested much earlier the following year. Winter onions also include perennial types that come back annually, whereas regular bulbing onions are typically grown as annuals.
Do Winter Onions Multiply?
It depends on the type. Perennial bunching onions and Egyptian walking onions multiply by forming new side shoots (divisions) or by planting their topsets. Overwintering bulb onions, like ‘Senshyu’, are usually grown as an annual crop from sets and will not multiply; they form a single bulb per plant. However, if left in the ground, they may occasionally produce a flower stalk and seeds.
How Cold Hardy Are Winter Onions?
They are exceptionally cold hardy. Most overwintering varieties can withstand temperatures well below freezing, surviving in soil temperatures as low as -10°F to -20°F (-23°C to -29°C) when properly mulched. The mulch is critical, as it prevents the freeze-thaw cycles that can heave the young sets out of the ground.
Can I Grow Winter Onions In Containers?
Yes, you can. Use a deep container (at least 12 inches) with excellent drainage holes. Fill it with a high-quality potting mix and plant the sets as you would in the ground. Container-grown plants are more susceptible to freezing, so you will need to provide extra insulation. Place the container in a protected location, like against a south-facing wall, and wrap the pot in bubble wrap or burlap to protect the roots from extreme cold.
Growing winter onions is a simple and rewarding practice that maximizes your garden’s productivity. By understanding what are winter onions and following these clear steps for selection, planting, and care, you can enjoy a very early and abundant harvest. Their resilience and versatility make them an indispensable crop for any gardener seeking fresh flavors straight from the garden, even when the growing season has just begun. With a little planning in the fall, you’ll be harvesting crisp onions long before your neighbors even get their spring crops in the ground.