I'm planning to plant some seeds, chrysanthemum, coreopsis, lambs ear, hosta, and milkweed. The chrysanthemum seeds say they have already been stratified, but none of the others say this. So I have a few questions:

Should I refrigerate all of the seeds?
Does it hurt to do this to the chrysanthemums that have already had it done?
How long should I do this for before planting them?
How long after refrigerating them can they then be planted (can they go straight from the fridge to the soil)?

I live in upstate New York, zone 5b : -15 to -10 (F). This weekend will get down to 30 degrees out, but from there on out, it will be getting warmer and warmer and stay above 32 degrees.

I keep all my seeds in frig, they stay good for years that way.
But ! On to your Qs? I dont believe !
That you have to stratisfy the others, unless directed to.
If your starting them inside under lites. Start them now. If outside. Wait till danger of frost is over, and keep in frig, till ready to plant.
Did i cover everything ?
😎😎😎

I also keep all my seeds in the fridge. My Heliotrope is from 1998 and all of them sprouted. One of my produce drawers is full of seed packets!

Yes, they can go directly from the fridge to the ground.

I take them out, plant the few I need and put the packets right back in the fridge so the chrysanthemums will be fine.

I believe all seeds that you purchase have been stratified. I read somewhere that seed companies store seeds in coolers before selling the next spring. If that's true the seeds went thru several months of coolness before getting to the stores.

Seeds that you purchase in packets are usually ready to plant; the stratification has been done for you. If you are working with saved seeds or traded seeds, you may have to do the work to stratify as needed.