I have had them outside in pots for several years now. By the end of the winter, the leaves have all turned brown and most will pull away from the crown easily. The first year or two, this led me to believe they were dead, but being slow to replant pots in the spring, I have been pleasantly surprised to see that they came back. I have even divided them once. I know they are marginal, and even more so for you, but, as I said, they can surprise you. If I were you, I would leave them alone until it really warms up. Who knows? Maybe you've gotten lucky.

I live in the UK and see Cordyline australis everywhere. Indivisa isn't so common though, I know there are some in very wet parts of the UK like some gardens in Northern Ireland and Devon. Occasionally we have a cold winter and there's a mass die off inland, but it's no big deal really. Most come back very strongly from the roots, especially if they were a large, mature plant before they died in the winter they reach their former size in a couple of years and come back very fast from a strong root system with fresh, new growth. What actually kills them is when you see well-meaning but misguided people wrapping them up in winter with bubble wrap and frost fleece. It's the worst thing to do in my opinion, these things hate to be soaking wet in winter and the frost protection people put round them just makes them rot. I don't protect my ones that are in the ground. If they die back they dieback, the soil doesn't freeze deep enough in Britain to kill them in most cases. Container ones i just put in a cold greenhouse to keep them from dying from the damp of winter which is the real cause of death. I have noticed a lot of variation in the plants grown here. Some are very narrow leaved, but mature plants are usually wide leaved, not sure if the leaves get wider over time or different varieties are tougher. I suspect the narrow leaved plants are the "Atlantic green" variety whereas the wider leaved ones are generic australis with maybe some indivisa introgression, although according to something i read somewhere the narrow leaved varieties are meant to be hardier. I've also never seen a mature, large plant of the red, pink or variegated varieties though i know some examples exist, they're probably less hardy and were perhaps selected from stock from the North island.

Hey Katob, I looked at Wal-Mart and they only have the Burgundy and Pink and green Cordylines and I decided to only get a fully green one that would be Cordyline Australis. I have seen that they are the hardiest Cordy. I think the others are 40-50 F at the lowest, and, I am not sure about heating my greenhouse. I am thinking of using a small shelter in the greenhouse and adding heat with lights or a small heater, BUT, I don't want to get anything too tender/tropical also. At least with the Windmill palm baby that I have IF I can keep it in a zone 7b to 8a, it should be fine, and the desert plants are all hardy to zone 5-6. I've got a Cholla tree, Yucca Rostrata, Agaves Parryi and an Agave Neomexicana X ??? I forget the hybrid that is mixed with the Neomexicana Agave. I've had my last Rostrata get too much rain last growing season, so, I have them staying in the greenhouse. I have a Yucca Recurvifolia and another Yucca with the big more fleshy leaves growing in a raised bed with mostly a gritty mix, they are fine despite too much rain. I may need to eventually move my Cholla tree to an in-ground bed, possibly the same bed with the Yucca's I see on the plant tag that it gets about 5 ft wide and even taller. For now, it will be in a medium sized pot. I am kinda wondering about how much to water my Yucca Rostrata. The soil is well draining, BUT, I wonder how moist to keep it. I guess dryish. I used mostly "palm and cactus" soil The Miricle grow stuff. My other stuff is grit, perlite and the bagged Palm and Cactus soil. The Wm that had the Burgundy Cordyline also had one that was green, but, not a normal average green, it was NOT Australis, though. I want another Australis, I may go to Ebay and look. Our Big box stores don't have much to pick from now.

Hello, did you ever find out an answer? I have the same issue on all 4 of mine. I live in San Luis Obispo