The best part about growing onions is that you can explore new varieties, with unique flavors and versatile uses each season. There are some varieties that will produce the most impressive bulbs, big enough to brag about among friends and neighbors.
Top 7 Giant Onion Varieties
Here’s a list of giant onion varieties to grow in the US and UK.
Starting with the Guinness World Record holder for the biggest onion in the world, weighing 15 lb 5.5 oz, Kelsae Sweet Giant is an excellent choice if you want to grow some of the biggest onions. While you may not achieve the size as big as the record-breaking onion, the bulbs will still be very large. Kalsae is a long day heirloom variety, suitable for northern growers, and is usually available as seeds.
The seeds are started indoors in late winters or early spring and the transplants are set into the garden 2 to 4 weeks after the last frost. Space the transplants at least 6” apart in rows spaced 18” apart for this variety to allow more room for developing bigger bulbs. It usually takes about 110 days to grow to full maturity after being transplanted in the garden.
2. Ailsa Craig Onion
Ailsa Craig onions are also a favorite variety of growers who seek giant bulbs. It’s a long-day heirloom variety, perfect for northern growing zones, that will produce globe-shaped large onions. The 5-lbs onions have pale yellow skin, with a mild, sweet flesh. Their mild flavors make them great for eating raw in salads as well as for cooking. On the downside, they’re best consumed fresh as they won’t last very long in storage. At best, you can keep them until mid-December when harvested around early autumn.
Ailsa Craig onions are widely available at garden centers and online as seeds, but sets are difficult to find. You can start the seeds indoors around February to mid-March, transplanting them in the garden as soon as the soil can be worked in early spring. Space the transplants about 4 to 6 inches apart and harvest them 110 days later once the tops turn yellow and fall over.
These hybrid varieties are intermediate-day onions that grow best in latitudes 32 to 45 degrees. Expression onions are usually available as seeds at garden centers and offer a good resitance to diseases. They grow attractive, slightly flattened bulbs with brown skins and can grow as large as 1.5 pounds.
The variety takes about 105 days to mature from transplants. Though they will survive for 3 to 4 months in storage, Expression onions are best consumed fresh. To grow the biggest Expression onions, plant the seeds in well-drained, fertile sandy loam. If your garden soil is heavy or compacted, amend it with plenty of organic matter several months before planting or grow the transplants in raised beds.
4. Sierra Blanca
Sierra Blanca, or Super Start onions, are a hybrid intermediate-day variety that produces huge globe-shaped onions with white skin and mild-flavored flesh with thick rings. With the best growing conditions, bulbs can expand to a diameter of 4 inches or more. They work perfectly in salads, onion rings and in recipes involving frying.
Sierra Blanca onions are available as seeds and take about 110 days to reach maturity from the time you set the transplants in the garden. In mild winter climates, you’ll achieve better results with fall planting while in colder climates, spring plantings work better.
5. Walla Walla
Walla Walla onions are a favorite of growers for their superior flavor, ease of growing and large size of bulbs. It’s a long-day onion variety, ideal for northern climates and has the potential to grow large bulbs, up to 2 pounds each.
The globe-shaped onions have a yellow to light brown exterior, with mild sweet flesh that can be used in many different ways in the kitchen. Since the flesh is juicy, Walla Walla onions won’t last very long in storage and are best used fresh.
They are usually available as seed which can be started indoors 6 to10 weeks before the last frost of spring. Plant the seedlings in the garden before all dangers of a heavy frost have passed and allow about 125 days for plants to mature and the bulbs to grow their full size before harvesting.
6. Ringmaster White Sweet Spanish
Ringmaster is a long-day hybrid onion that matures 100 days from transplanting, producing large, white onions, perfect for onion rings! The sweet, mild flavor makes it a favorite for many cooking applications besides fried onion rings. The bulbs have the potential to grow up to 5 inches in diameter so space the plants accordingly.
Since it’s a long-day variety, Ringmaster grows best in northern climates but can also be grown in warmer climates for an early harvest of green onions, though the bulbs won’t be as impressive. The globular onions have crisp, thick concentric rings forming firm, mild flesh, and can be stored for up to 4 to 5 months from the harvest date.
7. Big Daddy
Very resistant to the common onion diseases, Big Daddy is easy to grow in northern gardens and demands little care. It produces a good yield of flavorful onions that can be stored for up to 10 months from the date of harvest.
Other than the variety, the climate and growing conditions will also impact the size of harvest. Choose a suitable giant onion variety for your region from the list and provide it with the specific growing conditions it asks for to see those plump, spicy onions at harvest time!