Packing and stuff I read said 4 weeks before last frost - which is roughly now. No cold weather in 10 day forecast so I am going to plant them. What temps should I worry about? It will go below 30, likely below 25 in the next month.

Leeks are super hardy. A frost will not bother them.

All alliums are super frost-hardy. 10F is no sweat. Garlic can endure much lower.

Leek transplants are considered to be at some risk for bolting after freezes, but you probably could plant them now since you have them. The forecast I see predicts it will stay mild until it turns cold on Wednesday, hopefully letting them accumulate. Rainy weather may make it difficult to dig. If you can't plant them, you are supposed to keep them cool and dry.

Leeks can take frost and cold temps, yes. Leek transplants? IDK about that. If your overnight temps are predicted to stay in the 30s or warmer, probably ok to plant out. In the 20s? I wouldn't chance it. There is a big difference between a frost and a hard freeze; a hard freeze will likely destroy them.

Regardless of when you plant out, you need to harden them off first to acclimate them to the colder temps if they been stored in any degree of warmth.

If you do plant-out now, you might want to think about having frost blankets handy if the temps do get below 30s overnight. Not to protect from light frost, per se, but to protect those delicate roots to the degree possible by keeping a bit of daytime warmth in.

A hard freeze will not affect alliums. Been through many with mine. I *always* plant in November, and they go through hard freezes regularly.

I have no idea what your freeze cycles are like in Z9, but I have to ask - did your brand-new baby transplants go through a hard freeze, or larger plants that had a bit of time to establish themselves first?

I'll tell you exactly what they're like. Two years in a row we had brief temps below 10F in the winter. HIGHLY unusual, but as I noted in a recent post, USDA zones are for general guidance only. Can't depend on them absolutely for any given year. That's why you always buy perennials (trees, shrubs, at least) that can endure a few zones below what you're in. But almost every year we get temps down to 25F. As you should know, USDA zone 9 is rated for 20-25F winter temperatures. That's a hard freeze. In all cases (and I've been growing alliums for almost a decade) they come out of it happy with no protection. Well at 10K they sort of flop, but then pick back up when the weather gets warmer. These hard freezes typically happen in January, and we put in the alliums in November. I think what can hurt alliums is extended periods of hard freeze. Dixondale says explicitly that onion seedlings should be fine down to 20F. There are some varietal differences. Garlic is a rock. Almost impossible to kill garlic with low temps.

Huh. I wouldn't have thought you guys get that cold. Well, anyway, I personally wouldn't chance it, especially since they were mail-order (read: $$) not a $2 4-pack with 50 or so stuck in there so who cares if you lose them.

USDA Zone 9 DOES get that cold. It's on the books. (Well, we used to be 8b.) In some respects, because the USDA zones are just generalizations, and it can get violently cold when you don't expect it to, I suppose you're always chancing it.

Thanks guys! I planted them but I might protect them if it goes below 25. As we have discussed before some thing that a mature plant can take lower temps then a seedling. I have no hard evidence to support this but I think that might be true. Point is if leeks can take down to, say, 20 degrees I think a mature plant can take it more then a new seedling transplant. I could be wrong.

It was only $30 so not a big issue. Worst case I get some more. Maybe if it gets under 25 I cover some of them (less work then covering all and I got 70ish and only need about 40 leeks.