Overwintering onions

[Martin Mikulcik]

I haven't had much luck overwintering any onions to be honest. Shallots, Egyptian walking, green bunching. I think it must be freeze thaw damage because they're nominally hardy in northern Missouri if you believe the usda's zones So maybe better draining soil would work, or is a root cellar a better idea? My soil isn't even that heavy. In Kentucky they overwinter, at least in pots. I appreciate your advice

 

[Meadowlark]

It starts before you harvest them. Withdraw water about two weeks before harvesting. Some years Nature intervenes in this, and those years are the hardest to overwinter the onions.... but keep water off them as much as possible before harvest.

Next, dry the onions in full sun until the tops are obviously no longer bright green. Here that takes a day or less if the onions are in good shape, longer if they have had recent water.

Next, remove the tops and most of the roots without cutting into the onion bulb, place them stem up on elevated bed of hardware cloth, chicken wire or anything perforated so air can circulate. The bed should be located in a dark but open-ended shed which enables air circulation. I add a fan to mine 24/7 to aid air circulation.

No touching...onions should not touch each other in storage. No washing ever until you are ready to eat.

I like to hand squeeze my bulbs after sun drying and before storing to eliminate any/all soft ones. The soft ones will fail and take others out with them in storage. The hard, firm onions are what you want. Eat any soft ones first.

Don't fall for the BS about sweet onions failing to store. I grow the sweetest onion on Earth and store it from May to News Years Day if it isn't eaten first. Thanksgiving dinner is always with garden onions as is Christmas dinner around here. New Years Day sometimes we run out but never because of failed storage...they are that good to eat!!

I always start my crop in Oct. and harvest in the following May. That provides us fresh green onions starting in Jan. about when the stored onion bulbs from the previous season have all been eaten. No store-bought onions here is my standing goal...and it has been achieved most of the time for decades.

I'm inside for the night just now but if you or anyone is interested, I will post photo of this year's crop in storage tomorrow.

 

[Meadowlark]

Perhaps I misunderstood...thought you were asking about storage, but maybe not. Sorry.

If in ground is the question, mine stay in ground all winter growing. If started from seed and not transplant or sets, they have withstood 10 deg F lows. If transplants or sets, maybe 15 deg. F if you're lucky.

 

[Martin Mikulcik]

Perhaps I misunderstood...thought you were asking about storage, but maybe not. Sorry.

If in ground is the question, mine stay in ground all winter growing. If started from seed and not transplant or sets, they have withstood 10 deg F lows. If transplants or sets, maybe 15 deg. F if you're lucky.

Yes, trying to get onions i can grow by myself every year without having to buy seeds

And you know my climate is particularly difficult for onions, large bulbed ones especially. (We can do sets but that kinda defeats the point) We hit -10f most years in winter and 98 every summer. At this point I'm not worried about large bulbs. If i can just do bunching onions well, I'll be happy, but last year they didn't survive winter.

They grow great through the year though (the bunching onions) so I'm hopeful. I actually had one start growing in spring before it died before the last frost.

The walking onions survived winter but died shortly after mysteriously and the shallots i tried didn't survive winter. I've seen people do chives well but I've never got a packet to germinate.

 

[Meadowlark]

Here's an AI generated table which says the Egyptian are your best bet down to -30 deg F with mulch. That's pretty cold.

It says bulbs only down to 20 degF but I have been down to 10 deg F many times with great survival...but seed started are best survivors in bulbs.

Cold Tolerance of Onion Varieties​

Onion Variety	Species	Winter Survival Temp	Notes
Egyptian Walking Onion	Allium × proliferum	−30 °F (−34 °C)	Most cold‑hardy; perennial; survives deep freezes with mulch.
Welsh/Bunching Onion	Allium fistulosum	~10 °F (−12 °C)	Hardy but not extreme; good for zones 5–9.
Multiplier/Perennial Onions	Various Allium cepa types	~0–10 °F (−17 to −12 °C)	Hardy in zones 5+; less extreme than walking onions.
Common Bulb Onions (e.g., Walla Walla, Yellow, Red)	Allium cepa	~20 °F (−7 °C)	Typically killed by hard freezes; not reliable overwintering.
Shallots	Allium cepa var. aggregatum	~0 °F (−17 °C)	More hardy than bulb onions but still not extreme.

 

[Martin Mikulcik]

I'll try the Egyptians again, i don't know why they died this spring, so we'll see if we can't kill em and get more data

 

[nao57]

Supposedly ideal temperature to store onions would be about 50 degrees. But having said that I'm not an onion grower.

But... I do know that 50 degrees F is the line in the sand where bacteria growth slows down. Many plants you can store them well at that marker. So a root cellar thats shut up tight you could store them in there. That's probably the best bet, protected from frost.

But for root cellars, don't put apples near them because the gas emmitted from apples will make the other stuff spoil quicker.

Fruits that emit the most ethylene gas include apples, bananas, avocados, peaches, and pears. These high ethylene producers can accelerate the ripening and spoilage of nearby ethylene-sensitive vegetables like broccoli, cucumbers, and leafy greens. So plan to keep those a bit away from the other stuff that are more vulnerable to spoilage.

 

[Meadowlark]

Supposedly ideal temperature to store onions would be about 50 degrees. But having said that I'm not an onion grower.

I am an onion grower. I store my onions in an open shed for about 9 months with 7 of those months never reaching a temp as low as 50 deg F.

They are consumed by then so I dont know how much longer they would last but probably a full year. This based on decades of experience.

 

[skinyea]

I cheat and start them inside under grow lights. Always seeds
I start them the last week in dec or 1st week In Jan.

 

[Esther Knapicius]

Just heard about Welsh Onions . anyone grow them. supposedly can hand over wintering just fine. Did find seeds online.

 

[Meadowlark]

Just heard about Welsh Onions .

I don't grow them but would if I didn't prefer the large bulbing onions. They are reportedly easy to grow and similar to Egyptian onions except these are bunching onions and hardy to zone 3 coming back each year. I'd be interested in how they do for you.

 

[Martin Mikulcik]

Just heard about Welsh Onions . anyone grow them. supposedly can hand over wintering just fine. Did find seeds online.

They haven't yet overwintered for me (they're another name for bunching onions/scallions) but i think it's doable. They grow great as annuals regardless

 

[Esther Knapicius]

I don't grow them but would if I didn't prefer the large bulbing onions. They are reportedly easy to grow and similar to Egyptian onions except these are bunching onions and hardy to zone 3 coming back each year. I'd be interested in how they do for you.

Ill have to find the seeds and give it a go.

 

[Meadowlark]

I'd bet you can still start some now...but spring might be more reliable for you. Let us know how it goes.