Congrats!
I think as long as you have condensation on your containers, they should be alright.
more details can be found at the winter sowing faq's - or ask at the forums there.

Is this your first year winter sowing? I have only a few containers - it's my first year.
What else have you sown?

Here is a link that might be useful: winter sowing FAQ's

I've wintersown them several times. They do fine with minimal care. However, they don't get very big in their first year--especially when rabbits keep munching off the tops! Good luck.

Martha

Glad to hear they do well. I won't fret then. We live in a wooded neighborhood that is a peninsula bordered by a little river. My yard is one of the few with sun, and I want to grow natives that attract butterflies. For some unfathomable reason, we have neither rabbits nor deer. The woodchuck who used to live under our deck is gone as well. We do have some industrious beavers who felled one of my neighbor's prize dogwoods. I'm afraid the biggest threat is herbicides wafting from the neighbors.

Hi Nell, sounds like you have a nice place to grow gardens and a landscape full of natives. How nice to be near a little river! Do you have a dog? If so, they may help keep the critters away.

I wintersowed last year for the first time, with about 50 native species germinating (plus some cultivars), including Liatris pychnostachya and L. ligulistylis. They sprouted April 19-20th but then I planted them into small nursery pots to hold over because I didn't have enough garden beds ready yet. FInally got them planted in the fall. Mine didn't get very big the first year either, but probably would have done better if they were planted in the ground early. Yours are sprouting nice and early! Bill Cullina's Wildflower book says they may flower a little the first year (mine didn't).

This year I am sowing Liatris aspera too. What other plants are you growing for the butterflies?

From seed the butterflies are getting various Asclepias, Ceanothus americanus, various Eupatorum, Monarda fistulosa, Passiflora incarnata,Veronia noveboracensis, Cephalanthus occidentalis. I already have plenty of Chelone glabra and Echinacea purpura which I will move to the butterfly garden.
Nell