SEVERAL TIMES in Robert Frost: A Living Voice, his account of the poet's talks at the Bread Loaf School of English, Reginald L. Cook quotes Frost's remarks on "Birches." Frost's words on one such occasion are given a context by Cook, who writes:
In spite of his deprecatory view of explication, Frost revealed a good deal about his art. When he disclosed his feeling about certain words in "Birches," he gave a searching insight into what makes a poet's use of descriptive words stand up. And how cavalierly he did it! He offered "this little note on 'Birches' before I begin to read it. See. The kind of explication I forbid," he said self-consciously. Then with disarming slyness, he said: "I never go down the shoreline [from Boston] to New York without watching the birches to see if they live up to what I say about them in the poem." Invariably the listener laughed, but on the double take he realized that Frost, the careful craftsman, was confirming his assertion that birches bend to left and right by verification. Getting details right was a telling responsibility. His birches, he insisted, were not the white mountain or paper birch of northern New England (Betula papyrifera); they were the gray birch (Betula populifolia).
[. . . .]
The way in which Robert Frost came to write "Birches" is described by Elizabeth Shepley Sergeant: "As for the poet, 'who never saw New England as clearly as when he was in Old England,' he could not tie down his creative moments. It was about this time, early in 1914, while tramping the muddy yard at the Bungalow [West Midlands], that he suddenly; he says, wrote a new poem, not to be included in North of Boston. This was the now so famous and beloved 'Birches,' with its cold and crystal memories of another kind of wintry world." As this account suggests, Frost's poem might have reflected pure, almost spontaneous invention, but if so, it was stimulated by memories of boyhood experiences of winter and summer in northern New England and sharpened by the perspective of the poet's self-imposed exile. What I would suggest, however, is that in "Birches," even though Frost saw New England most clearly when he was in Old England, he re-viewed his wintry New England scene through Thoreauvian eyes.
On December 31, 1852, a day of rain and ice in Concord, Thoreau wrote in his Journals with keen anticipation: "It is a sort of frozen rain this afternoon, which does not wet one, but makes the still bare ground slippery with a coating of ice, and stiffens your umbrella so that it cannot be shut. Will not the trees look finely in the morning?" For the next few days Thoreau described the storm's "fine" effects upon the landscape. On the first day of the new year he observed: "This morning we have something between ice and frost on the trees. . . . What a crash of jewels as you walk! . . . The drooping birches along the edges of woods are the most feathery; fairy-like ostrich plumes of the trees, and the color of their trunks increases the delusion" (436-38). The next day Thoreau continued his report:
In this clear air and bright sunlight, the ice-covered trees have a new beauty, especially the birches . . . , bent quite to the ground in every kind of curve. At a distance, as you are approaching them endwise, they look like white tents of Indians under the edge ofthe wood. The birch is thus remarkable, perhaps, because from the feathery form of the tree, whose numerous small branches sustain so great a weight, bending it to the ground, and moreover because, from the color of the bark, the core is less observable. The oaks not only are less pliant in the trunk, but have fewer and stiffer twigs and branches. The birches droop over in all directions, like ostrich-feathers. 
Thoreau's description anticipates Frost's handling of imagery. But Thoreau's entry the next day offers an interesting variation on Frost's poem. He begins by recording that day's response to the observable beauty which can be attributed to nature's transforming and creative powers and then speculates on the comparative merits of man and nature. The first paragraph is largely descriptive of this "finest show of ice" (444): "Nothing dark met the eye, but a silvery sheen, precisely as if the whole tree—trunk, boughs, and twigs—were converted into burnished silver. You exclaimed at every hedgerow. Sometimes a clump of birches £ell over every way in graceful ostrich-plumes, all raying from one centre. . . . Suddenly all is converted to crystal. The world is a crystal palace" (445).
The next paragraph, however, moves into a new key. Stimulated by his last attempt at describing ice-laden birches, Thoreau ruminates:
I love Nature partly because she is not man, but a retreat from him. None of his institutions control or pervade her. There a different kind of right prevails. In her midst I can be glad with an entire gladness. If this world were all man, I could not stretch myself, I should lose all hope. He is constraint, she is freedom to me. He makes me wish for another world. She makes me content with this. . . .
Man, man is the devil,
The source of evil . . . .
I have a room all to myself; it is nature. It is a place beyond the jurisdiction of human governments. . . . There are two worlds, the post-office and nature. I know them both. I continually forget mankind and their institutions, as I do a bank. [445-46]
The conjunction of Thoreau's celebration of winter birches and his buoyant homily on man's inferiority to nature may be compared with Frost's similar conjunction of themes in "Birches." If man makes Thoreau "wish for another world " but nature makes him "content with this," to Frost it is when life most resembles nature—when "life is too much like a pathless wood"—that the poet would "like to get away from earth awhile." Frost would "climb black branches up a snow-white trunk / Toward heaven," but he would come back, he quickly decides, for "Earth's the right place for love." Thoreau would undoubtedly endorse Frost's aphorism. But their initial agreement would evaporate, I suspect, if each were to explain precisely what he took the statement to mean. While Thoreau would most characteristically focus on love of nature, Frost would just as readily assert the claim of man's fundamental love for man. The distinction is notable.
In the Journal passages that I have quoted above, Thoreau (for the moment read "man") appears almost exclusively as an observer, never as a participant beyond the act of perception. It is as if in nature's pure realm man's existence were suspended. Whenever Thoreau does tell in these entries what men are doing, or what they have done, he invariably does so to admonish them. Consequently, when he "climb[s] the bank at Stow's wood-lot and come[s] upon the piles of freshly split white pine wood," he does not compliment the worker for his labor, as one might expect, but decides, rather, that the owner of the woodlot is "ruthlessly laying it waste" (441). And in the same entry, a page or so later, he comments on the ringing of bells: "The bells are particularly sweet this morning. I hear more, methinks, than ever before. How much more religion in their sound, than they ever call men together to! Men obey their call and go to the stove-warmed church, though God exhibits himself to the walker in a frosted bush today as much as in a burning one to Moses of old" (443). Even when man does something well (after all, bells are a human invention), he is singularly capable of misinterpreting his own message and betraying his most noble purposes. For Thoreau the beauty and divinity which exist at this moment are in the glazed birch and the frosted bush. They are most certainly not in men. Nature and nature's workings are at the center of creation. In these pages Thoreau reserves his approval for the landscape transformed by ice and snow and the few men who make an appearance intrude momentarily along nature's periphery.
In Frost's poem, however, values are weighted somewhat differently. Its first twenty lines are largely devoted to a description of the effect ice-storms have on birches:
[quotes ll. 1-20]
The details in these lines are precise and deceptively neutral. The entire passage contains nothing to suggest that nature is superior (or inferior) to man, nor are we to infer that the two are equal. As description these lines exemplify what Frost calls the "matter-of-fact" of "Truth." But Frost does not stop with the conclusion that ice storms, and not swinging boys, are the cause of birches bent "down to stay." He approaches, finally the idea that man's acts upon nature have their own meaning and beauty: approvingly Frost decides that, given a choice, he "should prefer to have some boy bend" birches. In the midst of swinging, boys are not observers of nature; they actually collaborate with nature by taking the "stiffness" out of birches. Frost would have a bent tree signify that some boy swinging from earth, has gone beyond that "pathless wood / Where your face burns and tickles with the cobwebs / Broken across it." "Birches" suggests that nature's beauty is somehow enhanced when man has worked an effect upon nature. In this sense Frost's poem may stand as a qualified reply to Thoreau's recurrent strain of illimitable nature worship.
Of course there is another side to Thoreau with which "Birches" does not conflict. A Thoreau more congenial to Frost appears in a Journal entry six months before the notable ice storm of December 31, 1852. He writes: "Nature must be viewed humanly to be viewed at all; that is, her scenes must be associated with humane affections, such as are associated with one's native place, for instance. She is most significant to a lover. A lover of Nature is preeminently a lover of man. If I have no friend, what is Nature to me? She ceases to be morally significant" (163). For Thoreau this kind of bravely humanistic sentiment welled forth most clearly on an early summer's day. The dead of winter, we have seen, could evoke other feelings. But Frost's humanism became a harder, more durable thing in its midwinter setting of ice and snow.
As late as August 1919, in a list of poems that his friend John T Bartlett might like to read, Frost recommended "Swinging Birches." In some ways it is unfortunate that Frost stopped calling the poem by this title. I say unfortunate because the activity at the heart of the poem—the activity that generates whatever cohesion the poem has—is the boy's swinging of birches and the poet's ruminations on the possibility that the birches he sees have been bent by boys at play. He would like to think that such is the case. But since liking to think does not make it so, the poet turns to the more likely reason, the permanent bending of birches by ice storms.
You may see their trunks arching in the woods
Years afterwards, trailing their leaves on the ground
Like girls on hands and knees that throw their hair
Before them over their heads to dry in the sun.
Then, interrupting this train of thought—this "matter-of-fact" "Truth"—he returns to a consideration of the notion that by "swinging" them boys also bend trees (though not permanently, as ice storms do).
I should prefer to have some boy bend them
As he went out and in to fetch the cows—
Some boy too far from town to learn baseball,
Whose only play was what he found himself,
Summer or winter, and could play alone.
Here the poem shifts into a generalized description, a semi-dramatic account of the way such a boy proceeds:
[quotes ll. 28-40]
At this point the poet acknowledges that he, too, was once "a swinger of birches," and he admits that even now he dreams of being one again. When does he have such dreams?
It's when I'm weary of considerations,
And life is too much like a pathless wood
Where your face bums and tickles with the cobwebs
Broken across it, and one eye is weeping
From a twig's having lashed across it open.
To what sort of boyhood pleasure would the adult poet like to return? Quite simply; it is the pleasure of onanism. We do not need either Erica Jong or John Updike to remind us that "flying" is often a dream or linguistic substitute for sexual activity. But we do need to be reminded that "early orgasms at puberty induced by friction against a tree trunk" are "not an uncommon experience," to quote from a writer commenting on the following passage from the early diaries of James Boswell: "Already (age 12-13) in climbing trees, pleasure. Could not conceive what it was. Thought of heaven. Returned often, climbed, felt, allowed myself to fall from high branches in ecstasy—all natural. Spoke of it to the gardener. He, rigid, did not explain."
If physiologically there is some sort of pubescent sexuality taking place in the "swinging" of "birches," it is not surprising, then, that the boy has "subdued his father's trees" by "riding them down over and over again" until "not one was left for him to conquer" and that the orgasmic activity should be likened to "riding," which despite the "conquering" can be done time and again. One need only note that the notion of "riding," already figurative in "Birches," reappears metaphorically in Frost's conception of "Education by Poetry," wherein he writes: "Unless you are at home in the metaphor, unless you have had your proper poetical education in the metaphor, you are not safe anywhere. Because you are not at ease with figurative values: you don't know . . . how far you may expect to ride it and when it may break down with you." And what is true for metaphor and poetry is true for love. Frost insisted that a poem "run . . . from delight to wisdom. The figure is the same as for love. Like a piece of ice on a hot stove the poem must ride on its own melting." Then it is totally appropriate within the metaphor of "swinging birches" that even the storm-bent trees should look to the adult male like "girls on hands and knees that throw their hair / Before them over their heads to dry in the sun." No wonder, then, and fully appropriate it is, that when the poet thinks that his wish to get away from earth might by some fate be misunderstood such that he be snatched away never to return, his thought is that "Earth's the right place vor love." At some level of his consciousness the pleasurable activity of "swinging birches" has transformed itself into the more encompassing term "love." One might say, within the logic of this reading of the poem, that "Earth's the right place for [sexual] love," including onanistic love. The same sexual metaphor runs through the final lines of the poem as the mature poet thinks of how he would like to go but only to come back.
[quotes ll. 54-59]
From Robert Frost and the New England Renaissance. Lexington: The University Press of Kentucky, 1988. Copyright © 1988 by the UP of Kentucky.