I don't know how your weather is in TN but if you are going to have hard frosts, those seedlings won't make it. In Z5 we start sowing in January knowing we won't have 'sprouting' weather for several months.

Just for insurance, I would sow some more seeds in February if you have any left.

Coming from a different point of view, Susan, are you about a Z7 there? I think your seedlings should be fine with just the protection of the coverings on your containers. If you had an unusually cold night or storm in your forecast, you could always toss an old tablecloth or something over your containers until your temperatures moderate back to what they had been, or if really, really worried, temporarily move them. The three you mention are pretty darned resistant to cold temps.

I rarely have done anything additional to protect early germinators, but once in a while I'll lose confidence and move something important. Not to a warm room, but into a carport, under an evergreen shrub for some protection, can remember sliding a flat of something into the back of my Explorer one night for some insulation against a very hard freeze ;) Warm wouldn't be your goal, only a few degrees warmer, a bit of help.

I'm with morz on that. I'm in zone 7 and have seedlings coming up both in jugs and in the ground. My butterfly bushes are putting out growth at the bases and so are some other perennials. I'd leave them in the jugs, don't fry them in sun, keep them cool, and keep the lids on.

Actually, I do need to amend this slightly. Last week we dropped to 5 degrees and on that one night after the forecast, I brought mine in and then took them back a day later. Thats lower than normal for us. If you get any tender annuals up, these would be in danger. Hardy annuals and perennials are fine.

This post was edited by GreatPlains1 on Fri, Jan 10, 14 at 19:59

Ok great! Thanks you all. I'd say my microclimate is likely a 7b. We did get awfully cold for a couple of nights but we rarely go below mid 20s.
My seedlings are just so tall that they are going to push up to the top of the container if they keep growing.
What to do if that happens?
I really appreciate the guidance.
Susan

Usually the cold slows down the growth, but you'll have to prop open those tops some in some way if they start to crowd against them....

And that's when you will start wondering if you need to move them out of harms way (temps) depending on your forecast during specific periods in Jan and Feb. I had a big semi-clear plastic tote with lid that I kept in the basement, brought that out and put seedling containers of things in that overnight a few times on my deck. A larger garden pot overturned would work too (like Costco's clay that many of us have), even a bucket with a brick or something heavy on top if your storm included wind.

I don't have anything newly germinated I've had to worry about this year, but some cuttings, young plants, and my 4 yr old zonal geranium have gone in and out of my unheated garage more than one night. Dh has even gotten helpful, he'll ask, do you want that 'hydrangea' moved into the garage....Ummmm, it's a geranium, but yes, if you think it might drop below about 28F, it could come in ;)

What kind of container are they in??? That seems tall for as cold as its been. Mine that are up are tiny, up but tiny. What state are you in if I might ask? Climate zones don't tell much about conditions.

Thanks you all. Im in Middle TN, urban. Fenced yard southern facing. It's good to have a hubby to help huh? Regardless of what he calls the plants....
I have some of those large clear storage tubs...should I put them over the pans...I've sown in clear lasagna foil pans...
And what temps should concern me? Seems some of them are up and strong...other newer "babies" seem to have wilted during the 3 days of temps in the teens...
I just sowed my second batch and I need to get a third batch out there....
Should I get deeper pans?
Thanks for any and all advice!
Susan

Susan, you are colder than I'd imagined. Teens would be a rare weather event for us although we did have those temperatures for a few days in December, they aren't normal for us - about 10 degrees colder.

I would start to be uneasy about freezing of pots and damage to newest and small things at about 26F....even my hydrangea/geranium is OK as low as dipping to 28 overnight briefly.

If you are going down to teens, I don't think deeper containers would help protect things that may have germinated. That's cold. I'd have them in the storage tubs and covered with a tablecloth both.

Is this your usual weather pattern? You must have had some mild days for seeds to have germinated, usually they are good about reacting to temperatures and finding their own 'right time'. But we're dealing with mother nature too and she can fool us sometimes...

If you would usually go from almost Springlike then back to hard freezing most years, you may want to consider sowing a little bit later. This is supposed to be easy and the additional attention required only occasionally. This year at least it doesn't seem you can sow and forget. Sometimes its a bit of a learning curve to tweak this technique to fit your own climate.

Wonderful! Just the advice I needed. I am in a total "freeze thaw" world, this year worse than most. Maybe I am sowing too early. I may go ahead and sow some more since it appears I've lost some. I appreciate the advice to cover them. Would it be best to take them indoors when we get a "polar" wave? Thanks so much!
Susan

Indoors is usually TOO warm. Give them the equivalent to a tropical vacation for a few days and then you are committed to keeping them inside until you really are visited by Spring. And would have to recondition them to being back outside by gradually hardening off.

So no, indoors isn't typically suggested. A shed, unheated garage, storage container, cold basement, your car trunk ;), any of those things we talked about before that provide several degrees of protection without bringing in to a fully heated space. You really don't need to even worry about light since it should be such a temporary move.

Don't give up, you'll find the right timing for your own needs, just a little trial and error first.

Morz gives good advice. I don't usually sow until Jan. for hardy perennials and Feb. for most other things just to be safe. Unless we get a rare heat wave those times work for me because the seeds won't sprout until the conditions are right.

If it's common for you to have a mild december, but a colder Jan. and Feb., you might want to push back your sowing date so you don't get sprouts too early. You really want this to be as easy as possible and moving/covering seedlings should be a rare event, like in the case of a later-than-expected freeze.

Good luck with your seedlings. And you might want to consider 2L soda bottles or milk jugs in the future because they have more head room for the seedlings than a lasagne pan.

Caryl