Yes, it may be damaged by -10C/14F. However, plants growing in ground often re-grow from root crowns. Plant it out in a warm nook. Especially if you are quite near salt water it may do well for you.

I'm not near the water, rather up the mountain a way. I think I may lean toward leaving it in a pot. I just measured the plant and it's currently about 7 feet tall (in the pot.) The diameter of the frond ball is about 4 feet across. It's very healthy and in great shape.I'm sure you can appreciate why I don't want to loose her. Perhaps I could increase the pot size and continue what I have been doing?

At some point you're going to have an even bigger plant, these grow quite large where conditions permit. You may be rapidly approaching a time where you can no longer manage a potted specimen of such size.

Well, -10 sounds too chilly for cordyline / dracaena. That's zone 8, really?

My dracaenas survived the terrible winter of 2006-2007 sitting in black plastic nursery pots outdoors! They died back to the ground, but they came back vigorously in the spring. Being in pots is, of course, more stressful in the winter time than being in the ground.

If you planted it in the ground, you could protect the top with wrapping in the winter.

Boy I'm really on the fence now... I spoke with the nursery where I originally purchased the specimen years ago and they were surprised how big it had become... mind you they said my attention was not common as most people just let them die in the winter and buy new ones for their pots iin the spring. Their recommendation was to continue doing what has been working for me, in the pot and protected in the winter. I'll let you all know what I decide in September... in the meanwhile she's loving the heat! Thanks for your feedback.

In communities around Puget Sound specimens persisting in the ground and growing some yards high before freezing back are very common. I suppose most protected waterfront locations not dipping below minimum temperature for this plant with much frequency may have them grow nearly as large as in milder climates farther down the coast (Coos Bay and beyond).

An interesting thing a few years back was the freezing out of purple-leaved forms in nearby plantings, where the green-leaved ones on the same sites did not die back. When seeds of this species are planted purple-leaved variants are common. Local growers may segregate these seedlings into purple and green blocks before offering them for sale. The purple-leaved ones may vary in hardiness, with some being as reliable than as their more normal green brethren. Or there may be a genetic link between purple leaves and lowered cold tolerance. I don't know.

Well it's now November. I put my big girl into a larger diameter pot. I had to cut at least 9" off the bottom of the root ball to accomodate the broader but shallower new pot... it didn't phase the old girl at all. I am going to overwinter her in the car port again. Meanwhile my three purple cordyline which I purchased 3years ago at 9" high are three feet tall still in their pots. I will wrap them up as last winter and store close to the house. (I have put three other smaller ones in the ground as an experiment to see if they survive our Vancouver winter.) Will let you know in the spring. Thanks again for all you information everyone!

If you have a garage with a window or similar intermediate area just stick them in there during cold spells (Arctic fronts), putting them back out the rest of the time.

Put a thermometer there to make sure they are not getting too cold during a frigid spell, when frosts may penetrate unheated or lightly heated structures.

Will do... is there a way one can post photographs here?