In Gen 49:22, Jacob blesses Joseph in the following way:
Joseph is a fruitful bough, even a fruitful bough by a well; whose branches run over the wall.
As one commentary on Genesis wrote, what we have here is:
[T]he image is that of a young thriving vine planted by a fountain and thus well supplied with water, whose tendrils extend over the wall.—a fruitful bough] Or ‘A young fruit-tree’: lit. ‘son of a fruitful [tree’ or ‘vine’]. There is probably an etymological allusion to Ephraim (פְּרָת = אֶפְרָת) (John Skinner, A Critical and Exegetical Commentary on Genesis [2d ed; Edinburgh: T&T Clark, 1930], 530)
Latter-day Saints have often appealed to this verse as biblical evidence in favour of the Book of Mormon. The chapter heading to Gen 49 reads, in part, as follows:
Joseph is a fruitful bough by a well—His branches (the Nephites and Lamanites) will run over the wall
Diane E. Wirth wrote the following about this verse and it being valid biblical support for the Book of Mormon:
Throughout the scriptures, branches often refer to individuals in a genealogical sense (see for example Jeremiah 23:5, 33:15; Isaiah 11:1; Zechariah 3:8; and 2 Nephi 3:7). It is interesting to note that the people of pre-Columbian America also regarded the tree as an emblem of life and growth of a lineage or race.
When we examine Joseph’s symbolic blessing as given above, the pieces fall together when we see the well as representing the ocean. The descendants of Joseph—the branches—would cross the waters and multiply their seed in a land on the other side of the sea.
As it is in many cases with duo-symbolism of words, “branches,” in this case, may not only refer to members of a genealogical tree, but to a boat going over the wall of a well, or the sea. In the Egyptian Book of What is in the Underworld, the boat that travels in the waters of the underworld is called “Pa-khet” which, in English, translates as “branch” (E.A.W. Budge, The Egyptian Heaven and Hell London [1906], Vol. 1, pp. 47-48.) The duo-symbolism in this prophecy may therefore refer not only to the seed of Joseph, in a genealogical sense, but to a boat which his seed would use to cross the waters.
To support this hypothesis, we look to Moses to further amplify this prophecy. Moses said to Joseph’s seed that the land they were to inhabit would be “choice” and “bounteous.” He further indicated that it would be in the “ancient mountains” and “lasting hills” (Deuteronomy 33:13-17). The land they would be led to would be a land of plenty and it would contain an extensive mountain range. This description aptly applies to the Americas. The western hemisphere is not only rich in food and minerals, but it does contain lasting hills, namely the Rocky Mountains which run through the western part of North, Middle, and South America. (Diane E. Wirth, A Challenge to the Critics: Scholarly Evidences of the Book of Mormon [Bountiful, Utah: Horizon Publishers and Distributors, Inc., 1986], 116-18)
As with John 10:16 (see The "other sheep" of John 10:16: A Critique of the "Gentile" Interpretation), Gen 49:22, unlike that of Isa 29 and Ezek 37, would be viewed upon as valid prophecy related to the Book of Mormon peoples.
