I styled this hinoki cypress two and a half weeks ago. I have been allowing it to get sun until 1230-1pm and then move into the shade to prevent the growth that is no longer shaded out from getting sun burnt. It doesn’t look like that method is working. Not sure if this tip die back is solely from sun exposure, to much stress, inappropriate time for work. It has been treated alternating bonide mancozeb and copper as well as bonide systemic insecticide (acephate) and spectrocide malathion and only one application of talstar systemic granules in spring. Here are before and after photos of styling and then photos of this afternoon.
Looks like that branch may be dying back. Possibly damaged when it was wired or bent?
Are you seeing that kind of discoloration throughout the entire tree? If you have shade cloth to put it under that might be best, not sure how hot it is where you are. I assume you have checked out the hinoki aesthetics stream; I believe Ryan states that he would put the hinoki he was working on in a protected area for a couple of months.
Hinoki Cypress are notoriously brittle trees. It’s possible you broke that branch and didn’t even realize it. More likely though, at least in my climate zone, is that this is the time of year where you normally do see some browning of foliage, as well as small amounts of die back… I’m not exactly sure what’s going on here but I’d carefully examine the primary branch as well as the individual secondary branches for breaks. I know I’ve broken many branches and twigs on hinoki and not realized it until it turned brown. If that’s not the case, depending on your zone, you might still be okay and see minimal die back. All the real advice I can give aside from searching carefully for breaks is hold your breath and hope for the best!
Bear, I did some work on a new Hinoki this fall and had the same browning. I think it could be old growth dying back. I saw the same thing happen to Hinokis at the National Bonsai Museum recently. Hopefully yours has not gotten any worse since this post.