In Zone 8 we're supposed to be able to plant brugs in-ground. The tops will winter kill, but the plants are supposed to come back from the roots in the spring. It is recommended that we cut the tops down to stumps (before they freeze) & mulch over the root zone.
An option to that is grow the brugs in the ground, then dig them before fall frosts come, pot & store them where they won't freeze. Then replant them the next spring. With either method, it's a good idea to quit fertilizing them well before frost time, so their growth rate slows down & they'll go dormant more readily. I do this no later than mid-Sept.
I've overwintered potted brugs in my garage the past 2 winters. Some do well...others wither back nearly to the ground. The latter are mostly brugs whose parents came from warmer climates - the versicolors being one.
I'm already planning for next winter. Those that handled the chilly garage well can go there again. Those that had to regrow from the base this year, I will cut off the trunks, root them in water & keep them in my cool guest room over the winter. In so doing, I'll maintain the trunks with their Y's intact & can get flowers earlier next year. In our slow-to-warm climate, it takes a long time to regrow trunks from the ground up to the blooming stage.
Returning to your questions, I grew 1 brug in the ground last year & liked how it performed. I dug it up in the fall and put it in an 18-gal Rubbermaid tote, surrounding the root ball with potting mix. The plant has a versicolor heritage & the trunk withered back all the way to the root ball...I'm waiting to see whether it's even alive. Fortunately, it had more than 1 trunk and I kept 1 of those indoors, rooted in water. This year I will grow more brugs in-ground and leave the stumps out all winter. It's my guess that in most winters, our brugs will be challenged as much by wet soil as by cold temps. In a dormant state, they are not going to like having wet feet. I happen to have pretty sandy soil (tho quite amended where I plant brugs), so I'm hoping to evade the wet issue.
Finally, as for when to move brugs outdoors! I'm probably a little more conservative on this than most. I don't like to expose my brugs to temps much lower than 40, once I bring them out of dormancy. I moved my brugs out of the garage on 4/5, but lined them up against the east wall of the house where they are somewhat protected by the overhanging roof, as well as a large escallonia shrub. Yesterday I moved a few sanguineas to the backyard and I'll start moving the rest as soon as I can repot them...or prepare in-ground planting spaces for some. The sanguineas, like Allison's arboreas, handle chilly temps better than some of the other species & their hybrid progeny. If you have only a few & don't mind dragging them in and out when cold nights threaten, you can start bringing them out earlier than I do.
Robin, Sally (madamqueensally) is in Federal Way & she grows & sells a wide variety of brugs. Keep her in mind if you're looking for something specific. 2 of our members own brug nurseries & have excellent reputations: Brenda Delph from Seed Sprout and JT Sessions from Country Gardens. The rest of us, particularly those of us in the PNW, may be able to give you a few cuttings this spring if you don't mind pot luck. I'm sure I'll have a few to spare. Do you know the name of the one you grew last year?
Tom, we ARE getting a nice number of brug lovers in our region...I like your idea of having a get-together. Maybe you can organize that?! Hopefully I'm not missing anyone, but I think this is the list of our local members:
USDA Zone 8b
Heat Zone 3
Sunset Zone 5
SeaTac, WA...one cool place