when to transplant asters, mums, daisies, etc?

Keep in mind that many of those plants are bought by people who will use them as house plants for a month or two and then throw them away. If Madison's anything like upstate NY, you'll see those plants in stores until they run out. Here, that can be as late as Thanksgiving. If you want to plant them, the idea time is mid to late September, or more generally, whatever date gives them 4-6 weeks of UNfrozen ground so they can begin establishing a root system.

Optimally, I'd do all that in the spring. One trick you might use is overwintering them in the pot tucked into your leaf pile and covered with another inch or more of chopped leaves. Uncover as early as possible in the spring and transplant when the soil is workable again. It won't be 100% survival, but you should manage a goodly percentage.

Cheryl

The plants in question often struggle to survive in zone 5. Why would you not want to get them in the ground? In pots, their roots are more likely to suffer physical damage from repeated thawing and freezing.

I've done both - plant with about 50% success and over winter in pots on the ground shrouded in chopped leaves with 80%. I think the chopped leaves supply a more reliable temperature as they freeze and stay frozen while the main garden (being in full sun) has unreliable snow cover and the plants are subject to heaving. You could also sink potted plants to avoid heaving.

Good Luck,

Cheryl