My garlic and overwintering onions went down to 10F this winter for 4 nights (sunny cold days) and all made it through fine. Yours should be ok.

Down to 23 here the last two nights and my onions are fine.
YOPPER

Our low temps here get down into the single digits or below freezing, last year we had ( -15 F ) and garlic was unphased. Some garlic ( Hardneck reputedly taste best only in winters that have had an extended period below zero )

I overwintered Onions 'Candy' and Leeks 'American Flag' that were planted in November and they made it through fine. The biggest problem is not letting the soil dry out, they need an inch of water a week to maintain steady growth and good nutrients.

Nam

Thanks, I like these answers :-)

namfon,
can you expand on the over-wintering oif leeks and onions in zones 5/6? Did you plant seeds in November or transplants? If you planted transplants, when did you start them and what size were they? I'm interested in over-wintering in zone 5/6 and could use some advice - thanks

Leeks are similar to garlics and onions, with the same cold hardiness.
My leeks over wintered along with garlics and shallots last winter (low down to 14F).

novelist,

I planted the leeks on the 4th of July believe it or not. It takes so long for them to grow and they don't like it Hot or dry, so I grow them in the summer the same way that I grow Nightshades or other warm loving annuals in the spring ( I put them outdoors in conditions they like but keep them in pots so I can bring 'em indoors when conditions are not to their liking, which, for leeks is above 27C/80F ) The Onions were definetly an experiment so I won't say ( yet ) how well it worked. Since Onions are daylight sensitive I am very interested to see if they bulb up or not, I have these planted in the same bed as this year's crop of 'Candy' Onions so that I can compare the results.

I transplanted the Onions and Leeks outdoors several weeks before I thought the winter would kick in and tell them to 'sleep', which, last year was mid November.

So they were 4 months from seed but still very small plants because I kept them in their seeding trays ( which were recycled fruit berry containers ) I am not going to say how well this worked until I see the results but, so far the onions are about the same size as the ones I planted this March and the leeks will be hilled this weekend.

Our lows this winter were just above freezing - not below zero this year.

Hope this was not too wordy

OK, great - thanks for that explaination. I was thinking something along the same lines - transplant in early November. I plan to start leeks, onions and shallots in my indoor grow room in August and get them up to transplant size for November. It's a new experience for me too, so I'll try and chronical my progress.