#Joseph is a fruitful bough

Here "Joseph" is a metonymy that stands for his descendants. Jacob speaks about them as if they were a tree branch that produces a lot of fruit. This emphasizes that they will greatly increase in number. (See: [[:en:ta:vol2:translate:figs_metonymy]] and [[:en:ta:vol1:translate:figs_metaphor]])

#bough

a main branch of a tree

#whose branches climb over the wall

Branches that grow and extend over a wall are spoken of as if they were climbing. (See: [[:en:ta:vol1:translate:figs_metaphor]])