When is it best to grow clematis Autumn or Spring?

[Ashville5]

We didn’t have much luck with the one we planted this spring.

Its generally better to plant all shrubs and plants in autumn as the ground is warm from summer and they will be able to concentrate on getting their roots down before top growth in spring.

similar question but I ordered 2 Clematis mayleen yesterday. Is it better to plant in the soil this week or just put it in a bigger pot until next spring. I think one I would liek to keep in a very big pot long term but the other will go in the back of a border so in the soil.