Onions Sprouting in Storage: Curing, Variety plus Storage Spot
Onions sprouting in storage are reacting to warmth plus storage conditions. UMass Amherst Extension notes high temperature increases sprouting, high humidity stimulates root growth plus the two together raise the chance of rot.
The short answer
Store onions at 32°F plus 65 to 70% humidity, as UMass advises. Dry bulbs at 75 to 90°F for curing in a ventilated spot for two to four weeks until necks are tight. Pick storage varieties, since storage potential depends on variety, plus onions from seed store longer than those from sets.
Why do stored onions sprout?
UMass notes high temperature increases sprouting plus advises cooling gradually to avoid condensation. It notes maximum storage life before sprouting comes when foliage is still 30 to 40% erect. Nebraska Extension advises harvest when about two thirds of tops have fallen plus necks have started to dry. It notes waiting more than one or two weeks past that can cause bulbs to rot or grow again.
How does curing work for storage onions?
University of Minnesota Extension advises a warm, ventilated area at 75 to 90°F for two to four weeks until outer scales are dry plus the neck is tight. Nebraska notes onions with poor curing do not store well. It advises leaving at least one inch of stem when tops are cut, or braiding dried leaves. It advises not washing bulbs.
| Factor | Target | Source |
|---|---|---|
| Curing temperature | 75 to 90°F | Minnesota plus Nebraska |
| Curing time | 2 to 4 weeks | Minnesota |
| Storage temperature | 32°F | UMass |
| Storage humidity | 65 to 70% | UMass |
| Stem left | At least 1 inch | Nebraska |
| Seed or set | Seed onions store longer | UMass |
Source: UMass Amherst Extension, Nebraska Extension plus University of Minnesota Extension.
Which onions store longest?
UMass notes storage potential depends on variety plus that onions grown from seed store longer than those from sets. Minnesota notes storage onions there are long day types, while sweet or mild onions are short day types. Minnesota notes too much nitrogen gives large necks that resist curing plus poor storage quality. Nebraska advises using bruised or thick necked onions soon rather than storing them.
How to: step by step
- Pick when tops start to fall plus necks soften.
- Handle bulbs gently to prevent bruises.
- Hold bulbs warm plus airy two to four weeks.
- Trim tops to one inch once necks are dry.
- Set aside thick necked bulbs for kitchen use.
- Store cold plus fairly dry.
Troubleshooting
Sprouts in a warm room: heat. UMass notes high temperature increases sprouting.
Roots on stored bulbs: excess humidity. UMass notes high humidity drives root growth.
Soft necks in storage: poor curing. Minnesota notes it leads to decay.
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Sources
- Harvesting and curing onions, Nebraska Extension in Lancaster County
- Harvesting and curing onions, UMass Amherst Extension Vegetable Program
- Optimal storage conditions and ethylene sensitivity of fall storage crops, UMass Amherst
- Growing onions in home gardens, University of Minnesota Extension
FAQ
When should onions be pulled for storage?
Nebraska Extension advises harvest when about two thirds of tops have fallen plus necks have started to dry. UMass notes the longest storage comes with tops 30 to 40% erect.
How much stem should stay on a stored onion?
Nebraska Extension advises leaving at least one inch of stem when tops are cut.
Do sweet onions store well?
University of Minnesota Extension notes sweet or mild onions are short day types, while storage onions are long day types.
Should onions be stored in the fridge?
University of Minnesota Extension notes home refrigerators are cold plus dry, which is fine for long storage of onions.
Do onions from sets store as long as onions from seed?
No. UMass Amherst notes onions produced from seeds store longer than those from sets.
