Hardening off seedlings

I was wondering how big the seedlings have to be to be hardened off. I imagine they have to have their true leaves and can't be tiny can they? Thanks for any help.

If you treat your seeds the way nature does, you don't have these problems! I sow my seeds in pots outside in the autumn, then prick them out into cells. I've had several outside frozen or covered in snow when less than 1" high, and lately it's been raining day and night on them. Because they're all toughened nature's way, they can take it.

If you start them inside, they grow fat and flabby cells which don't support them well, so the sooner you start hardening them off, so that they grow smaller cells closer together, the better.

Mary,
Thanks for your information. I did the winter sowing method (70-80 containers!) but needed something to tide me over until the warm weather has arrived.

Hi Lorie!
I've successfully hardened tiny seedlings. I sometimes think the smaller they are the better off they'll be. You have to keep an eye on them while they're small and make sure they don't dry out. Start them off in a shaded sheltered area on a mild day. I put mine on my porch where it's semi enclosed. You can gradually move them out into more sun and more exposure as they get stronger.

Lorie, I'm guessing from your question that you HAVE started your seedlings inside, and while Mary's advice is true for many plants, the proverbial horse is already out of the barn. And winter sowing doesn't work well with tender annuals, especially if your winters are harsh and/or you're apt to have a late freeze, as is the case in a lot of North America.

There is no one answer here - it depends on the plants you've got, and how warm your days are getting, etc.

Generally speaking, plants need to be fairly good sized, and ideally they'll have several true leaves before you begin hardening off, especially if your weather is cool and/or windy (or the opposite extreme - very hot!)

Being in PA, extreme heat is probably not the problem right now. But cold and/or windy may be. If you purchased seed and happened to save your seed packets, there should be some directions for when to harden the plants off. If not, why don't you post a list of the plants you have, and their sizes (and when you planted them); and we'll help you sort out the timing of hardening them off.

You may know this already, but you'll need to be prepared to closely monitor your seedlings after you set them out; they'll go out for a short time, in a very protected spot in the beginning, and you'll lengthn the amount of time they spend outside day by day, as well as gradually introducing them to more hours of sunlight each day. Their water requirements will likely increase during this time, so be prepared to water them more frequently.

All of which is another reason why winter sowing can be a good idea for many plants, as the time spent to "baby" your plants is greatly reduced.

Go_vols,
I have a list a mile long, well not really that long. LOL
Right now, I have lupine (6-8 inches), daylily (7"), perennial sweet pea, crazy daisy, astrantia and sundrops. None of these are really small, (not under 5"). I have them on a partially sheltered porch and I haven't been bringing them in at night. We are getting 50-60 degree weather. I was figuring on a week in the shade and then they should be able to stand the sun. Am I right?
Thanks for all your help.

You're more than halfway there if you've kept them in that cool location for quite a bit already. I'd suggest shade to start, and then gradually add more sun each day, but a week or two of gradually introducing more sunlight should do it, depending on how your weather goes.