You plant chrysanthemums now, or plant in spring.
Douglas County Nebraska
Most chrysanthemums are not hardy enough to survive winter here, they are planted in late summer for fall color and will die. Even the "hardy mums" that you buy this time of the year are rarely hardy enough to withstand our winters.
If you are looking for a perennial mum to come back year after year, be sure to search for one that states that it is perennial, not just hardy. You can also plant a variety of asters that have similar characteristics to mums but are hardy. You can plant perennial mums and asters in either spring or fall, depending on availability.
You can find more info here: https://extension.unl.edu/statewide/douglas-sarpy/pdfs/ce/resources/ce-g1711-garden-chrysanthemums.p...