Where in BC are you located? As long as you have not experienced any hard freezes and the ground can still be easily worked, I'd opt to plant the Sibes in the ground as opposed to containers. These are tough plants from a harsh native environment - they don't call 'em "Siberian" for nothing :-)) Ditto Dutch iris or any other bulbous forms - plant them in the ground now.

Hmmm... Both. We have had a couple good frosts but the ground IS still workable. I am in zone 5b, the Okanagan Valley, and our first frost was 2-3 weeks late as it was. Last night was only our second, our first was Wed. night.
So... still plant 'em or what? They will be here late this week (the Sibs) and the Dutch next week. I guess I am wondering where to draw the line.

Well, your interior climate is a good bit more extreme than my coastal one, but here I don't draw a line :-) Planting and gardening continues throughout the winter. I don't think you should look for a "magic" date but let your conditions guide you. If your soil is still workable, you can still plant.

FWIW, I once planted a client's mixed perennial border, including an assortment of bulbs, on December 17th, only hours before the temps dipped into the teens for a protracted cold spell. Didn't lose a single plant and the bulbs bloomed on schedule.

Not so much of a magic 'date' I was looking for, just criteria. Which you have given me. I understand that pushing the envelope can compromise some plants the following year, but now realize that irises (especially SIBES) are not one of them. Thanks alot for the info!

The problem I've had with fall planting of siberians is that they have long, narrow root systems, and are easily squeezed out of the ground by frost heaves. One of the few plants I've had that particular problem with, BTW. It's not a problem with large transplanted clumps which can easily contain 50 rhizomes, but purchased divisions are much smaller.

With the volume of water in Okanagan Lake, your climate should have considerable moderation. After all, even peaches are grown around Penticton. You should have nearly ideal conditions for many kinds of iris. I'd say, go for the ground planting.

If frost heaving is a problem, put a triangle of good-sized rock, either river rock or rough mountain rock, around the plants. These work both as heat-sinks, moderating the day-night temperature cycle, and as weight to hold plants in the ground. They act as a kind of mulch too, moderating moisture loss, which is part of the winter damage source in the Columbia Basin and the Snake River Plain, and I would think, also in your NNW-SSE oriented deep valley terrain.

Winter burn on evergreens, both broadleaf like Boxwood, and conifers such as Arborvitae, was serious where I lived on the Idaho-Oregon border, NW of Boise, a climate somewhat like yours but a little milder (supposedly). They would recover in the spring, however.

Neil Mogensen

we have peaches up here too:-) Not grown so much commercially but about 15 minutes down the highway is where the "peach zone" really starts. Okanagan lake ends here so just north it becomes less semi-arid and more agricultural and forest. It is a pretty wonderful place in all for growing. If you are ever in BC everyone you should check out the Okanagan Valley, it is lovely. Wineries, orchards and such.