I have Tree Collards from a cutting.
Existing problems
1.Slow growth leaves.
2.Curving Leaves
The Tree Collards are growing height wide but the leaves are slow growth.
I am currently using miracle grow soil and miracle grow plant feed.
I administered one application of miracle grow plant feed.
Please advise on how to promote leaf growth .
Thank you in advance .

I admit I had to look up tree collards—new to me! And I got to reading about them. Hopefully someone here who has actually grown them will respond to you. Meanwhile, I don't know if you've seen this website, but these folks are serious about tree collards and provide a TON of detail plus a video about starting them from cuttings. Apparently it's a s l o w process. Hope it helps.
https://www.projecttreecollard...

I grow collards but not tree collards. So my knowledge is second hand. It is a perennial plant which has somewhat slow growth at start. Also best adapted to zones 8-10 as it it succumbs to temps below 20 degrees Fahrenheit. There are alot of online videos so Yo may want to look at those. https://www.bing.com/videos/ri... https://www.hortmag.com/edible...