No, these can be planted in the ground at any time the soil is workable (not overly saturated). They are more likely to be better off in the ground than in small nursery containers anyway, as the smaller soil mass and greater exposure to colder temperatures increases the risk of root damage in nursery containers.

But having said that, most retail nurseries in the area maintain a pretty full stock of containerized conifers throughout the winter months exposed to the elements without any significant risk. And a good number of gardeners, myself included, grow a selection of conifers in containers on a year round basis without problems.

Roots are more tender than tops and may be damaged inside containers without the tops showing it by wilting or turning partly brown. The first to go are the younger roots on the outer edge of the root system, especially if plastered against the pot walls these may freeze and die fairly readily (perhaps in the 20s F for some kinds). The effect of this may instead be slower top growth the following growing season.

Thanks for the help. All plants are in the ground. Need to stop buying more!