Cortland

Onion

Zone 12a Save Garden

🌱 90d to harvest Bulbing

Sweet, mellow, and richly aromatic, Cortland yellow onions form handsome bulbs with a warm golden-brown skin and a tender, juicy …

Crop Dates

Milestone	Date
Start Indoors	Nov 6th
Last Frost	Jan 1st
Transplant / Sow Outdoors	Jan 1st
Harvest Begins	Apr 1st
Harvest Ends	Dec 31st

Crop Details

Trait	Value
Days to Maturity	90
Sun Requirements	Full Sun
Growth Habit	Bulbing
Support Needed	None
Planting Depth	Normal
Germination Temp (°F)	75
Min Soil Temp (°F)	45
Min Night Temp (°F)	28
Harden Off (days)	7

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Frequently Asked Questions

What pest or disease issue most commonly affects Allium cepa (Cortland onion), and how do I treat it?

Onions (Allium cepa) are especially prone to fungal downy mildew and botrytis/neck rot during cool, humid weather. Remove any infected foliage immediately, improve airflow by spacing plants and avoiding overhead watering, and water at the base in the morning so leaves dry quickly. If problems persist, use a labeled fungicide effective for downy mildew/neck rot on onions and follow the label for intervals and application timing.

How often should I water Cortland onions during the main growing phase?

During active bulbing (once the plants are established), keep soil consistently moist but not waterlogged—aim for roughly 1 inch (2.5 cm) of water per week, split into 1–2 waterings depending on heat. Check moisture by feel: the top 1 inch should be moist, not soggy, and stop short of pooling to prevent rot. When bulbs begin to size up, you can taper slightly to avoid excess moisture that encourages neck rot.

How can I tell when Cortland onions are ready to harvest?

Harvest when about 50–75% of tops have fallen over and the remaining foliage is starting to yellow, typically around 90 days for Allium cepa. Gently lift a bulb: the skin should be papery and tight, not wet or peeling easily. Harvest on a dry day and leave bulbs on the surface to cure briefly before moving them to a warm, airy spot for proper drying.

Sweet, mellow, and richly aromatic, Cortland yellow onions form handsome bulbs with a warm golden-brown skin and a tender, juicy interior that tastes wonderfully balanced—never harsh. The flesh stays crisp and succulent at harvest, making Cortland a standout for fresh slicing, caramelizing, and roasting, as well as for silky sauces and classic pickled preparations. Grow for a reliable 90-day rhythm and enjoy a harvest that turns everyday meals into something special with its gentle, sunny flavor.

Sowing Tips

Transplant Conditions

Wait until soil reaches 45°F and nights stay above 28°F before moving outdoors. Harden off for 7 days first.

Expert Note

For best storage bulbs, keep transplants growing steadily (consistent watering and weed control) and stop irrigation a bit before tops lodge to cure the necks.