By Barbarak
North Yorkshire,
United Kingdom 
This is a photo of the top part of a Red Lucky magnolia. Bought from T&M this spring. It produced a bit of foliage but no flowers ( it's in Container). The topmost growth died back in September . I decided to trim the stems back as there was no green on the scratch test, however there was the black mark that you can see. I don't know what it is and whether it will kill the whole tree, so I have only trimmed back to stem with foliage. Hope someone can help.
23 Oct, 2019
Answers
When you cut the stem down, did you make the cut close to the side branches as it's difficult to see by the photo?
If you leave some of the branch too long, then it will continue to die back into the live stem. If this isn't the case, then as Seaburngirl says, get in touch with the supplier as I think they should supply a replacement.
24 Oct, 2019
thanks , have done as you suggested and sent photo to T&M. sorry photo always seems to invert when taken with I pad.
24 Oct, 2019
Just an update. T&M couldn't suggest what was wrong with the magnolia but thought it looks deadwood. Have refunded price even though there is live foliage on the plant.
30 Oct, 2019
That is excellent news. T & M have gone up in my estimation.
30 Oct, 2019
That does not look good. I would get in touch with the supplier with the image and ask for their advice/replacement .
23 Oct, 2019