VegetableOnion
Utah Yellow Sweet Spanish Onion
The Utah Yellow Sweet Spanish Onion carries the honor of being Utah's official state vegetable, personally recommended by Utah State University for its exceptional performance in western growing conditions. This heirloom long-day variety produces massive golden bulbs that can weigh over a pound and stretch up to 6 inches across, developing their signature mild sweetness over 110-115 days from seed. Hardy across zones 2-9, these impressive onions combine the satisfying size of Spanish varieties with surprisingly good storage capabilities for a sweet onion.
Photo © True Leaf Market
Growing Conditions
USDA Zone
2-9
Sunlight
Full Sun
Water
Moderate
Soil
Well-drained, Fertile Loam, Moderately Rich
Growth Stats
24 in
Height
Spacing
3
Plant Profile
Sunlight
Full Sun
Water
Moderate
Zones
2-9
Size
24in H x ?in W
Growth
—
Care
Moderate
Hover over chart points for details
Highlights
What sets this variety apart is its remarkable size combined with gentle sweetness, creating bulbs that can easily exceed a pound while maintaining the mild flavor that makes Spanish onions famous. Officially endorsed as Utah's state vegetable, this heirloom demonstrates exceptional adaptability for western climates while offering moderate pink root tolerance that helps ensure reliable harvests. The combination of substantial storage life and sweet flavor makes it uniquely versatile among large onions.
Common Uses
These large, mild onions excel as slicing onions for sandwiches and burgers, particularly prized on patty melts where their sweet flavor and substantial size create perfect rings. Their gentle taste makes them ideal for grilling whole or in thick slices, while their size and mild character work beautifully in marinara sauces, chili, and hearty stews where they add body without overwhelming other flavors.
Growing Timeline
No timeline data available yet for this variety.
Care Instructions
Start Indoors
Seeds can be started indoors for early transplants, giving gardeners a head start on the 110-115 day growing season.
Direct Sow
Sow directly 6-8 weeks before the final spring frost or 4-6 weeks before first autumn frost. Create shallow 1-inch deep trenches and sprinkle the small seeds generously, covering with just 0.25 inches of soil.
Harvesting
Harvest when the green tops have dried out, yellowed, and begun to bow over naturally. Mature bulbs will display light brown skin with white flesh underneath. Loosen soil around bulbs to check for consistent coloring, then pull on a sunny day and allow them to cure in the sun for two days before storing.
Growing Calendar
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Companion Planting
Pests & Diseases
Ecology & Traits
Edible
Scientific Classification
Allium cepa
Family
Amaryllidaceae
Genus
Allium
Native Status
L48 (I)
History & Origin
“This heirloom variety earned its place in agricultural history when Utah State University officially recommended it as perfectly suited to the state's growing conditions, eventually leading to its designation as Utah's official state vegetable. The variety represents the Spanish onion tradition brought to American gardens, where it found particular success in the western states' climate and soil conditions.”