Unknown Ceroid

[Peter]

I understand that the habitat for Pachycereus pringlei, aka Cardons, is northwest Mexico/ Baja California. That being the case, the plants will know little or no frost. That stated, they do have tough skins and could possibly withstand a reasonable degree of cold, perhaps with some scarring. Given no choice as to where to overwinter the plant, I'd keep a diligent eye on it.

I have a few of these plants and they do respond to regular potting on, however my opinion is to let the plant reach the optimum size for the place it's kept then let it go into 'growth slumber'. There's little point in letting it get larger and larger just for the sake of it, unless you have unlimited space, of course. Mature Pachycereus pringlei are the largest cacti in the world, if I'm correct.