Onion, Bulb
Allium cepa
Bulb onion forms a storage onion over a long cool season of about 90–120 days from planting with seed, sets, or transplants. Day-length type must match latitude, and steady growth early plus dry-down late produce firm bulbs that keep well. Hardy plants can go outdoors from several weeks before the last frost through the frost date.
Plant family Amaryllidaceae · Also called storage onion
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Match day-length type to latitude.
Plant outdoors from four weeks before the last frost through the frost date, or start seed indoors 8–10 weeks before frost at 1.3 cm depth. Germination takes 7–14 days when seed is used.
Harvest basis is planting, covering seed, sets, or transplants. The key tip stresses matching short-, intermediate-, or long-day varieties to the site’s latitude.
Use this range as a planning baseline and adjust for local conditions.
Use this range as a planning baseline and adjust for local conditions.
Use this range as a planning baseline and adjust for local conditions.
Use this range as a planning baseline and adjust for local conditions.
Give bulbs room to expand.
Allow 10–15 cm between bulbs with rows about 30 cm apart. Compact spacing suits sets; seed-grown plants may need thinning to the same band.
Containers need 25 cm depth and about 7 litres per position. Bulbing requires depth for root expansion and stable moisture.
Core measurements
Crop-level planning range.
Crop-level planning range.
Crop-level planning range.
Crop-level planning range.
Allow for the mature form of the selected variety.
Install support early when it is required or useful.
Keep moisture even until necks soften.
Six hours of direct sun minimum supports bulb sizing. Shade produces tops without adequate bulb enlargement.
Moderate water at 25–35 mm weekly with pH 6.0–7.0. Reduce watering as tops begin to fall to encourage dry skins for storage.
Sunlight
Full sun (6+ direct-sun hours/day)
Soil pH
A suitable acidity range for general growth.
Weekly water
Moderate water need.
Aim for even moisture and water deeply when the upper 2-3 cm of soil begins to dry.
Time maturity from planting material.
Count 90–120 days from planting regardless of starting method. Lift when tops yellow and necks soften, then cure in a warm, airy place.
No succession interval is listed because a single spring planting typically fills the season. Day-length mismatch shows up as scallions without bulbs.
Read with the full crop profile.
Read with the full crop profile.
Read with the full crop profile.
Read with the full crop profile.
Select a short-, intermediate- or long-day type suited to the site's latitude.
Onion, Bulb growing questions
What are short-, intermediate-, and long-day onions?
They respond to day length during bulbing. The key tip says to choose a type suited to your latitude.
Can bulb onions be grown from sets?
Planting material includes seed, sets, or transplants with harvest measured from planting.
When should bulb onion tops be bent?
Allow natural yellowing and drying before harvest; premature bending is not in the dataset but even moisture early matters.
How long from planting to harvest?
90–120 days from planting with harvest basis planting.
Profile values are crop-level planning ranges compiled from sources S1,S2,S3,S4. Local climate and variety can change actual results.
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