VegetableOnion
Walla Walla Onion
Sweet Onion
The Walla Walla onion carries a romantic tale from the Mediterranean to the Pacific Northwest, where a French soldier's discovery on the Island of Corsica eventually became Washington's signature sweet onion. These extra-large bulbs with light brown skin and crisp white flesh mature in 125 days from transplants, producing jumbo-sized onions famous for their exceptionally mild, sweet flavor. Hardy across zones 2-9, they thrive as long-day onions in northern regions, reaching 14-24 inches tall with their distinctive green tops that can be harvested as scallions along the way.
Photo © True Leaf Market
Growing Conditions
USDA Zone
2-9
Sunlight
Full Sun
Water
Moderate
Soil
Well-drained, Fertile Loam, Moderately Rich
Preferred Temp50-75°F
Growth Stats
24 in
Height
—
Width
3 in
Spacing
125–125
Days to Harvest
PeriodBiennial (Grown As Annual)
TypeBulbing - Long Day
Plant Profile
Sunlight
Full Sun
Water
Moderate
Zones
2-9
Size
24in H x ?in W
Growth
Biennial (Grown As Annual)
Care
Moderate
Hover over chart points for details
Highlights
What sets Walla Walla onions apart is their legendary sweetness and size, developed through over a century of careful selection for the sweetest and largest bulbs. With 95% water content and remarkably low acidity, these onions are sweet enough to eat like apples and transform any barbecue dish with their mild, crisp flavor. The green tops provide a bonus harvest as scallion-flavored stems, while the main bulbs can grow 3-6 inches across. Their cold-hardy nature makes them especially suited to northern growers and the Pacific Northwest, where they've become a regional treasure.
Common Uses
Walla Walla onions excel in fresh applications where their sweet, mild flavor can shine without the harsh bite of more pungent varieties. They're prized for barbecue dishes, where their natural sweetness complements grilled foods, and make exceptional onion rings due to their tender texture and large size. Their low acidity makes them perfect for eating fresh in salads, sandwiches, or even raw like an apple. The green tops can be harvested early and used like scallions, providing a dual harvest from a single plant.
Growing Timeline
First Bloom
Not Applicable (Harvested Before Flowering)
First Harvest
90-120 Days After Planting
Last Harvest
Determinate
Care Instructions
Start Indoors
Sow seeds indoors 6-8 weeks before the last frost date in 128-cell trays, planting 1 seed per cell and covering with 1/4 inch of soil.
Transplant Outdoors
Transplant outdoors when soil can be worked, spacing plants 4 inches apart in rows 12-18 inches apart. Unruly tops may be clipped to 5 inches at transplant time.
Direct Sow
For direct sowing, create shallow 1-inch deep trenches at least 12 inches long, sprinkle the very small seeds generously, and cover lightly with 1/4 inch of soil.
Harvesting
Harvest Walla Walla onions when the green tops have dried out, yellowed, and begun to bow over naturally, typically around 125 days from transplants. The green stems can be picked earlier for scallion use once they reach 8 inches tall, usually around 90-100 days from sowing. Loosen the soil around bulbs to check for consistent coloring and allow them to dry further in the ground before lifting. The bulbs should be 3-6 inches across when mature.
Pruning
The green tops can be harvested when they reach 8 inches tall for use as scallions, and any unruly growth can be clipped to 5 inches at transplant time to help establishment.
Growing Calendar
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Companion Planting
Ecology & Traits
Edible
Scientific Classification
Allium L.
Family
Amaryllidaceae
Genus
Allium
Duration
Biennial (Grown As Annual)
Growth Habit
Bush
Native Status
L48 (I)
History & Origin
“The Walla Walla onion's journey began over a century ago on the Island of Corsica, off the coast of Italy, where a French soldier named Peter Pieri discovered a remarkable sweet onion seed. He carried this precious find to Washington's Walla Walla Valley, named "many waters" by the Native American Plateau tribes. Through many years of patient selection, choosing only the sweetest and largest onions for seed, Pieri and later growers developed what would become the famous Walla Walla Sweet Onion. This Italian heritage, refined through decades of careful cultivation in the unique conditions of the Pacific Northwest, created a variety that would eventually gain recognition from state universities and become synonymous with the region itself.”