hello Mango
I live just north of Montreal and my plumeria s have bloomed a couple times for me.
What I would do is to bring them in at night and put them back out in the day until daytime temps. reach no lower the 10 cel.
then I would bring them in and keep them under lights.you should have blooms with in a month by the looks of the inflo.after they bloom' wait for the inflo to fall off and ease up on the watering until spring...
cheers and good luck

They don't need much water so it'd be better to keep them on the dry side during winter. Soil would only need to be just damp. Cold and wet would be their undoing.

What I do is wait until the mix dries out, then use a sqeeze bottle and water only along the edges along the inside of my pots trying to avoid letting water touch the trunk.

I let most of mine just drop their leaves naturally by taking away light, to the point of darkness, and let them rest. I put them under light at the beginning of spring to give them and early start. By the time spider mites and other evil critters start to attack them, it is time to stick them outside.

It has been a huge success with mine. Good luck!

Mike

I am in the Montreal region too. My plumerias came in about 3 weeks ago. One is blooming for the first time this week. I don't let them go dormant completely but grow them on the dry side in the winter.

I am from Barrie Ontario but spend winters in Florida

Hate to tell you how easy they are to grow down here

You just take a cutting off of one of your own or someones plant. Stick it into the very poor sandy soil down here and the darn thing just simply grows No fussing with them but some fertilizer gives more bloom

Of course you can buy plants, at several places There is one very specialised

grower in Tampa. Well there are growers all over the place who really go loopy over Plumeria
I do like the yellow ones best myself. THey bloom down here not til April or so. And then apparently most of the summer But I am not here to see them, for most of their bloom time