Hopkins never says who the figure in this poem is. We get only a pronoun, "his", and then a flood of detail: tanned cheeks, tangled hair, a hat stuck with wildflowers. The "down" on those cheeks suggests someone young, a boy or a young man, though that is my reading of the word. What the poem cares about is not the person's story but the way he looks, and how much of that look seems to have been borrowed from the countryside around him.
Almost every image comes from the hedgerow or the farm. The opening line makes the cheeks themselves into a plant. The soft growth on them is a "furl of fresh-leaved dogrose", like young leaves just unrolling. The sun, "forth-and-flaunting", has "swarthed" him "with lion-brown". "Swarthed" is a verb built from the idea of swarthiness, and the sun comes across as a showy painter at work. The tan is a lion's colour, so the boy is grand as well as weathered. The final clause, "Before the Spring was done", gives the portrait a season and a hint of how quickly it was achieved.
The second and third stanzas turn to his hair, and here Hopkins stacks up comparisons without choosing between them. It is like "a ravel-rope's-end", frayed hemp with "hempen strands in spray". It is also like "a juicy and jostling shock / Of bluebells sheaved in May", and like "wind-long fleeces on the flock / A day off shearing day". "Shock" works two ways, as a thick mass of hair and as a bundle of cut stalks, so the human and the harvested overlap in a single word. The line "Fallow, foam-fallow, hanks—fall'n off their ranks" shows the same crowding. Its stresses jam together and the hair tumbles down in a heap. The sense of "disarray" is built into the sound as well as stated. The sheep comparison is a good one, too. The fleece is at its fullest the day before it is cut, so the hair is shown at its most abundant and untamed.
The sound of the poem is as busy as its pictures. Hopkins is known for what he called sprung rhythm, which counts stresses in a line rather than syllables. It lets him set strong beats side by side, as in "forth-and-flaunting" or "juicy and jostling", where the alliteration makes the words nudge each other like the bluebells. The rhymes are mostly tidy in the first three stanzas: down/brown, sun/done, spray/disarray, shock/flock, May/day. They hold the loose imagery in a neat frame. In the second stanza the rhyme gets playful, with "ranks" echoing "hanks" inside a single line.
The last stanza breaks that neatness. It grows to six lines, and the final line is a long, winding sentence: "And the sunlight sidled, like dewdrops, like dandled diamonds / Through the sieve of the straw of the plait." The hat is decked with a rose, or failing that "Rough-Robin or five-lipped campion clear", a casual substitution that shows how little the wearer fussed. The "beauty-bow" is a decoration made from whatever was growing nearby. Then the light itself becomes a character. It "sidled" like someone slipping in sideways, and it is "dandled", a word we use for bouncing a small child on the knee. The straw weave becomes a "sieve", and the sunlight falls through it in glittering drops. The repeated s-sounds of "sunlight sidled", "sieve", "straw" and "plait" give the line a hushed shimmer. The poem begins with the sun darkening his skin and ends with the sun playing in his hat, so the light frames the portrait.
The poem as given trails off into a row of dots. Judging by that, it is unfinished, and the ending may be an accident of survival rather than a choice. Even so, the fragment shows Hopkins's way of seeing at its most concentrated. He notices particular things, such as a rope's frayed end, a campion's five lips, or the weave of a hat, and he coins compound words to hold them. The portrait is warm rather than reverent. Nothing in it is idealised or distant, and the young figure seems to belong to the same world as the bluebells, the flock and the light. That sense of a person fully at home among living things is what makes the fragment worth reading closely.