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Onions
General information
- Allium cepa, Onion
- Amaryllidaceae family
- Sunlight: full sun.
- Soil conditions: Well-drained, fertile soil.
- Can be planted from seeds, sets, and transplants. Onion bulbing is triggered by day length.
- Short Day varieties form bulbs when day length reaches 10 hours. Can be grown in the North. Intermediate Day varieties form bulbs when day length reaches 12-13 hours. Can be grown in most areas except far North, and Deep South. Long Day varieties form bulbs when day length reaches 14 hours. Grow best in northern areas including Delaware.
View/download as a PDF >
Successful cultivars
- Big Daddy (110 days) Spanish style, yellow onion. Long Day. Good storage onion.
- Walla Walla (80-90 days) Big round onions, sweet, mild, juicy flesh. Long Day.
- Red Candy (95 days) Glossy red, sweet, mild flavor. Intermediate Day.
Common pests & diseases
- Onion Maggot
- Leafminers
- Thrips
- Downy Mildew
- Leaf Blight
- Onion Rust
This publication was created by Master Gardeners Rick Judd and Gail Hermenau. Photos courtesy of Gail Hermenau.
UD Cooperative Extension
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In accordance with Federal law and U.S. Department of Agriculture policy, Cooperative Extension is prohibited from discriminating on the basis of race, color, national origin, sex, age, or disability.