Dark is the forest, and the first thing Edward Thomas gives us is a place with no obvious way in. In twelve lines we meet stars, riders, hidden dwellers and two kinds of flower, yet nobody in the poem ever reaches anybody else. Its subject is separation: a forest that divides one crowd from another and one flower from another, and perhaps the familiar world from something we cannot get to. The poem never says what lies on either side, and that silence is the point.
The opening stanza lifts a farmer's language into the sky. The stars are "seeds of light", and the verbs "sown" and "bred" turn the night into a field. Then come two small words, "In vain", which undercut the picture. Either the brilliance is wasted on the forest below, or the seeds will not take root in ground this dark. Thomas does not choose between them. The sentence that follows is bent into an old-fashioned shape, "not since they were sown was bred / Anything more bright", with the verb ahead of its subject and "bred" left hanging at the line-end. It sounds like an incantation, and the stars are praised even as they are made useless.
In the second stanza the poem grows stranger. "Mighty multitudes ride / About, nor enter in." We are not told who they are. They might be the stars wheeling overhead or a ghostly cavalcade, and the poem refuses to say. What matters is the pattern. A second group, "the other multitudes that dwell inside", is set against the first, and the word "other" makes the two crowds mirror each other, one circling the edge and one hidden at the centre. The stanza ends flatly: "Never yet was one seen." Notice that "in" and "seen" are the only pair in the poem that does not quite rhyme. The sound reaches for its partner and misses, just as the two multitudes do.
Stanza three brings us down from the sky to the ground, and colour appears for the first time: the "purple" foxglove inside, the "gold and white" marguerite outside. After the abstraction of the earlier stanzas, these flowers are almost startlingly ordinary. Yet even a human gesture as simple as picking a flower cannot cross the divide, because "those that pluck either blossom" cannot "greet / The others". Here the rhyme does some quiet work, pairing "marguerite" with "greet", so that the flower sits beside the very act of meeting that is denied. The closing words, "day or night", echo the starry darkness of the opening and rule out any hour when the barrier might lift.
The form supports this sense of fixed order. Each stanza rhymes abab, which gives a steady, ballad-like regularity, and the lines alternate between a long one of about ten syllables and a short one of five or six. The short lines ("Hang stars like seeds of light", "Anything more bright") land like doors closing after the longer lines have opened a view. The rhythm is also not a plain iambic march. "Dark is the forest and deep" falls away from its heavy first beat in a way that feels slower and more spell-like than ordinary speech. There is no "I" anywhere, no witness to be sad or surprised, so the division reads as a fact of the world, stated calmly.
This calm is what makes the poem linger. It is short and almost bare, but it leaves a great deal unsaid. A reader might hear in it the gap between the living and the dead, between what we know and what we only sense, or between any two groups who live side by side without meeting. The poem supports each of these readings without insisting on any. The stars, riders, dwellers and flowers become symbols that point at something without naming it. By the last line we are left where the riders are, on the outside of the trees, looking at a darkness that keeps its secret.