Welcome Emily.

I have succefully ws just about every Z:4 hardy perennial. I started listing them but it was too long a list. Hardy perennials can be sown anytime after solstice. Some need a period of cold to germinate ( ie: delphiniums).

At the top of the ws forum page is a link to the FAQ which has a several questions/answers about which seeds will work. Also wintersown.org has helpful information including a database of successful seeds sown for each zone.

Check those out and if you still have questions about certain seeds we will try to help.

Here is a link that might be useful: Database seed germination 2006 Z:4

I will second what mnwsgal said. Any hardy perennials will do great :)

I have great success with annuals too, but I usually wait until mid to late February to ws those.

Anything hardy to your zone is great to start now- or as soon as you can walk outdoors an get far enough away from the door to drop the container with out tripping yourself up when you turn around and hurry back inside before you freeze all you nose hairs and get your fingers frost bit....
- 20 below last 2 mornings here....
And you can keep wintersowing till you no longer need a jacket when you go outside- so some years- that ud be about half way through June....
Really- You will LOVE it! It is THE best way to garden in zone 4 in the winter! and Spring- and Fall too!!
Emily- Please say that you have your bags of Miracle grow indoors all thawed and ready to go? They can take days to thaw with this cold we are having!
You will be a forever fan when you try it just once!