Just don't expect it to be blue- it's lavender.
No different care than any other dahlia- you can start it inside & plant it out when the danger of frost has passed.

I am in Quebec like you! I like to get a head start in mid or late April by starting them inside - just near ordinary light, and they are fine. Huge beautiful blooms mid or late August right through to frost. Some bloomed late July.

BLUE BAYOU IS GORGEOUS ON THE PLANT BUT DOES NOT MAKE ALONG LASTING CUTTING FLOWER.

lizalily, have you heard of the trick of using an open flame to 'cauterize' the end of the stem right after cutting? It prevents and air bubble form forming in the stem which would block water vase water from reaching the flower. Yes you are right some dahlias definitely last longer as a cut flower that others.