The toughness of purple cabbage

Last fall/winter in 2011 I bought four purple cabbage at lowes. I was being lazy, so I Just put them in four black plastic pots. What has surprised me is that they are still alive and growing quite well in those same plastic pots. They survived the hot dry california summer, sitting in full sun. We had highs of 109 some days. I knew that they had some cold tolerance, but taking that heat without being planted in the ground? I didn't even give them ample water. Any thoughts?

Also unsure of why, but i've also found them tougher. Where my green cabbages were full of cabbage moth the red ones right beside them were untouched. Could have something to do with the more pronounced 'spicy' flavour of the red cabbages? I know that radishes are hotter with less watering, so perhaps the red cabbage also possesses some form of this mechanism.

by red, i also mean purple.