This poem depicts an English speaker who is abroad and missing home very much. The arrival of the season of spring in England is making his longing for home especially hard.
Browning uses a great deal of imagery in order to paint a vivid picture of England's beauty in the spring. He describes, for example,
the lowest boughs and the brushwood sheaf
Round the elm-tree bole [that] are in tiny leaf,
While the chaffinch sings on the orchard bough
We can imagine, in our mind's eye, the small buds on the trees and the blooms on the orchard boughs which are not yet heavy with fruit. We can also envision the "blossomed pear-tree in the hedge," as well as the "clover / Blossoms and dewdrops." Further, there is the auditory imagery of the "chaffinch sing[ing]" as well as the thrush, and so on.
The speaker uses personification when he describes the thrush as "wise," as though it is a creature that could knowingly experience the feeling of "rapture." The buttercups are also personified as being able to be woken up by the noon, and all the creature and plants are personified as being "gay" when the sunshine comes.
The tone of the poem, how the author feels about the subject, is indulgent and understanding. He does not judge or disapprove of the speaker's longing for home. He gives the speaker keen powers of observation and memory. The speaker's yearning for England in springtime seems absolutely reasonable, as though the author agrees with him. The poem conveys the theme that there is simply no place like home. Who knows where the speaker is; springtime is probably beautiful there as well, and, yet he just wishes to go home.