Where I live, plants such as this don't survive in the out of doors, so I see them only in conservatory settings. I was surprised to learn from your photo and caption that euphorbias like this benefit from pruning. I love the other photos you've posted of this same species, especially the ones of the blooms. Fascinating plants.

As you might have guessed, this was a pretty serious job. Perhaps more along the lines of pollarding.

More here:

https://garden.org/thread/view...

and if you scroll down to the end of that thread you can see some of the chat on the subject yesterday.

Thanks for the reply and the link. Though I picked up this response a couple of months late, I was able to scroll/step backward from the most recent entries and find the conversation on the topic of pruning and raising this tree euphorbia.