Thank you so much, poet.
If you'll allow me to make one comment, it would be that I'd like to have seen "I grew tall and proud" expanded a little; as it is, I read it like one of those "Two years later..." signs inserted for a jump ahead in time. (On reflection even now, I mentally inserted a period or colon after 'grew', and that changed it for me.)
Interesting you say that. The thing I struggled mightily with when writing this poem was the pacing. For better or worse, my decisions on that front were deliberate, including the rather abrupt jump.
Everything from "years coiled round" forward has been in almost word for word since my first draft or two, so that part was not the problem. That was the punch of my poem, and it came easily.
But I spent a lot of time pulling my hair out about how to balance the first half, partly for the reason you cite.
I finally decided that the poem was really about the ending, and it was the refusal to be felled that led there, not so much the success in growing tall. I thought putting much emphasis on growth, success, etc. would undermine the conclusion, which was, damn, the tree did its thing, and it's tall and everything, and that's just great, but will anyone care when it falls? And while I considered discussing that others had tried to chop the tree down during those years, I thought that made the poem less powerful rather than more. (I hinted at it a bit, I hope, with "one by one, they passed me by", which I wanted to have dual meaning.) Anyway, in the end I decided that should be a touch before moving on to the years passing and thickening (the intransigence, as William so aptly put it).
I worried a lot that the proposal/Christmas tree part was too top heavy, and that the tone was off from the rest of it. But after wrestling with it for quite a while, I finally decided I wanted the second stanza to be more rushed and crowded, to have a bit of a harried feel, and to get in something of the fear not only of being clipped and restrained, but also of mind-numbing routine (in my alliteration, I hope), before I escaped, with a deep breath, to (what I hope is) the more contemplative tone of the rest.
Whether I succeeded, or those were the right decisions, I guess is up to the reader. But that was why I did it the way I did.
Apropos of nothing, I set myself the challenge of working the tree metaphor all the way through the poem without ever mentioning the words "tree," "pine," "limb," "trunk," "sap," "forest," "twig," "roots," "bark" or "branch." (And I had a tempting place for every one of those. Puns? I had a few.) I couldn't resist needles, though.