Have no experience with the cultivar, 'Tree Collards', but the regular type grows quite well in GA. Stumbled upon a forum recently, where a lady in Beaumont, TX said she had success growing the tree variety, but that they required shading from the afternoon sun, daily watering and the yield was not as good as the low growing one's.
There is a kale variety that also grows into the tall form, widely cultivated in Europe, where it's called "Walking-stick kale", a name derived from drying and polishing the stalks, whereupon they are used as walking-sticks.
Kale does not do well in this part of the South, due to summer heat. It is similar to collards, but leaf is smaller and thinner, plus a more pronounced bitter taste.
Both can be harvested and eaten throughout the year, but most people prefer the taste after the plants have been subjected to a couple of frosts. That can be simulated by picking the leaves and placing them in the refrigerator for a couple of days, before cooking. Adding a small amount of vinegar to the cooking water, also improves the taste.
Have you rooted the cuttings?
Why not give them a try and let us know of your success?
Brassica is a very healthy food, when consumed in moderation, that contains calcium and other vitamins, especially Vitamin K and is said that it prevents cancerous cells from forming.
Rb

I grow Kale well in the fall, winter and spring. Since our spring has been cool, I'm still having good luck with it (cut mine way back and has re-sprouted fresh leaves). I grew walking stick Kale by accident for two years because someone sent me an incorrectly labeled plant. It was 99% stick and 1% leaves all summer. I would agree that growing it in afternoon shade would be advantageous.