What a massive dull struggle this was. For the record, I like the theme a lot. The idea of embedding a poem in its entirety is interesting, and WILLIAMCARLOSWILLIAMS is a poet I'm fond of. It's interesting that the poem's name, THELOCUSTTREEINFLOWER has the same number of letters as its author's name. The poem in use is the second version, much pared down to its essential images.
I don't really mind that sometimes the poem's words are embedded in longer entries, whereas in other answers, the word in question is a separate thing. That being said, the best ones are MASTIFF and CUCAMONGA. GREENING is not a word I want to see in the puzzle.
That's it for the theme. And the price we pay is the fill. My goodness, I was unhappy with the fill. So many, many, many abbreviations. How would you like it if I wrote the blog post entirely in abbreviations? It wd gt anyg qkly. And so does this puzzle.
TKT UNH VAC (I don't even know how that gets in) CPA MNO (better than the others) RRR (hmmmm) TLC SLR CTN AAA SPCA MSN YTD GTOS LTS BRB SOC TCM ANAT (not actually a subject on the MCATs, but whatever) REC EXO EDS GST. Wow, that's a lot. And when one abbreviation crosses another, it can be a total guessing game (like GST and SPCA).
Beyond those, we get ANGERER, IRONERS, ELIST, and SALIENCES, all of which I have major problems with for one reason or another. Not to mention your usual gaggle of crosswordese. You know, there really ought to be a collective noun for crosswordese entries. I nominate a "shrug of crosswordese." OTO, CYAN, NANO, EDO, IODATE (blah), etc. etc.
Things I liked in the fill: GLIA, for obvious reasons. 98D: What may make you duck down? (EIDERS). 71D: Harp's home key (CFLAT) - which I didn't know and would never have guessed. Why not B? Not clear even after research on the Interwebz. BUTCHERED is a good word. I enjoyed PEGLEG crossing ROLLINGGAIT, as I imagine those two would go together. And an opportunity was missed somehow with 99D: Certain salt, to connect in with those other two.
It was a slog, and I didn't enjoy myself.