Lucky for us Southern Oregonians, it doesn't get as snot-freezingly cold here as it does in places like, say, the Midwest. But it does get cold enough at times (remember that cold snap in December of 2009? Nine degrees overnight?!) to do in those perennials you're so looking forward to, if they're only potted in containers and sitting on a patio or deck.
Before the mercury drops is the time to start considering these things (that'd be NOW), so here are a few things to think about in preparation for next spring and summer, if you've got container-planted perennial flowers.
What Are My Options, Doc?
There are basically three choices here: overwinter outside, overwinter in a protected environment like a shed or garage, or overwinter indoors.
1. Overwinter outside. This is a fine option for hardier plants. (This is a poor choice for delicate ornamentals that are being grown out of their zone unless you're feeling somewhat homicidal toward them.) Check out this video for some tips on what to do.
2. Overwinter in a protected environment. This is good for slightly less hardy plants, but you still have to deal with the chore of lugging them to a tool shed or making space in the garage for them. If you're bringing plants into a protected area for the winter, check on water and light needs for each plant type. Some plants prefer to spend the winter in a dark, cool room, dormant. Others will die.
For these first frosts, tucking potted plants up against your house is usually enough to protect them from damage.
3. Bring 'em in. For more on this option, check out Overwintering Potted Plants Inside.