I think that I shall never see

A poem as lovely as a tree. . .

Well, Joyce Kilmer's effort didn't really give trees a run for their money. In my opinion Walt Whitman did the job with "When I heard the Learn'd Astronomer" in 1900.

When I heard the learn'd astronomer;
When the proofs, the figures, were ranged in columns before me;
When I was shown the charts and the diagrams, to add, divide, and measure them;
When I, sitting, heard the astronomer, where he lectured with much applause in the lecture-room,
How soon, unaccountable, I became tired and sick;
Till rising and gliding out, I wander'd off by myself,
In the mystical moist night-air, and from time to time,
Look'd up in perfect silence at the stars.