The name of the poem is suggested indeed by the Bible story of Ruth the gleaner, but the story in the poem is only that of a rich farmer who marries a very poor girl, because of her beauty and her goodness.

It is just a charming picture--a picture of the dark beauty which is so much admired in Northern countries, where it is less common than in Southern Europe.

There are beautiful brown-skinned types; and the flush of youth on the cheeks of such a brown girl has been compared to the red upon a ripe peach or a russet apple--a hard kind of apple, very sweet and juicy, which is brown instead of yellow, or reddish brown.

But the poet makes the comparison with poppy flowers and wheat.
That, of course, means golden yellow and red; in English wheat fields red poppy flowers grow in abundance.

The expression "tressy forehead" in the second line of the fourth stanza means a forehead half covered with falling, loose hair.
The foregoing pretty picture may be offset by charming poem of Browning's describing a lover's pride in his illusion.