(Mr M forgot to log in again!-- MM)
It is a matter of natural sentence flow and stress for meaning. Let's write it like a prose sentence:
I think that I shall never see a poem as lovely as a tree.
Spoken in conversation, sentences carry several levels of stress, not
just stressed and unstressed. This sentence would probably be
uttered with primary (main) stress on
poem and
tree-- these are the core words of meaning here-- and with secondary stress on
lovely-- this adjective essentially defines the relationship between
poem and
tree. Below that would be tertiary stress on the simple subject (
I), the simple predicate (
see) and the negative word (
never)-- notice that
all of these stresses appear in the dependent clause, not in the matrix clause (
I think),
which only colours the core statement about poems and trees. (I
should include a caveat that others may find differing stress patterns,
and different intent would also produce others)
Trees is written in iambics, which as you probably know is a
common rhythm of spoken English. To a certain extent, we tend to
talk that way, and iambic stress patterns will impose themselves on our
utterances. It is probably a circular phenomenon, actually-- we
tend to speak in iambics, and so sentence structure and patterns of
idioms and stock phrases are therefore formed and preserved in iambics.
Blank verse is iambic; it just does not rhyme. I think you mean
free verse.
Free verse depends on rhythms set, not by syllables, but by the cadence
of phrases, images, and syntax. It should be relatively easy for
you to learn to feel the difference if you recite aloud (as you should
all poetry) this excerpt from Matthew Arnold's
Dover Beach:
The sea is calm to-night.
The tide is full, the moon lies fair
Upon the straits; -on the French coast the light
Gleams and is gone; the cliffs of England stand,
Glimmering and vast, out in the tranquil bay.
Come to the window, sweet is the night air!
Only, from the long line of spray
Where the sea meets the moon-blanch'd land,
Listen! you hear the grating roar
Of pebbles which the waves draw back, and fling,
At their return, up the high strand,
Begin, and cease, and then again begin,
With tremulous cadence slow, and bring
The eternal note of sadness in.
And compare it with some of Thomas Grey's
Elegy Written in a Country Churchyard:
The curfew tolls the knell of parting day,
The lowing herd winds slowly o'er the lea,
The ploughman homeward plods his weary way,
And leaves the world to darkness and to me.
Now fades the glimmering landscape on the sight,
And all the air a solemn stillness holds,
Save where the beetle wheels his droning flight,
And drowsy tinklings lull the distant folds:
Save that from yonder ivy-mantled tower
The moping owl does to the moon complain
Of such as, wandering near her secret bower,
Molest her ancient solitary reign.
Beneath those rugged elms, that yew-tree's shade,
Where heaves the turf in many a mouldering heap,
Each in his narrow cell for ever laid,
The rude Forefathers of the hamlet sleep.
Now, which one is free verse, and which is in metric verse?