Analyzing this allegory is fascinating. It is so full of deep doctrine and history concerning the house of Israel. I know these next two quotes are long but if you take the time to read them you will understand this whole chapter better!
"The use of the olive tree as a symbol for the house of Israel is an excellent example of how God uses symbolism to teach his children gospel laws and principles. For centuries the olive tree has been associated with peace. War and its grim attendants of destruction—rape of the land, siege, and death—were hardly conducive to the cultivation of olive orchards, that require many years of careful husbandry to bring into full production. When the dove returned to the ark, it carried an olive leaf in its beak, as though to symbolize that God was again at peace with the earth (see Genesis 8:11). The olive branch was used in ancient Greece and Rome to signify peace, and it is still used in that sense in the great seal of the United States where the American eagle is shown grasping an olive branch in its talons. The only true source of peace is Jesus Christ, the Prince of Peace. His peace comes through obedience to the laws and ordinances of the gospel. These laws and ordinances are given to the world through the house of Israel, symbolized by the olive tree. Someone once said that Israel was not chosen to be an uplifted people, but an uplifting people.
There is further symbolic significance in the cultivation of an olive tree. If the green slip of an olive tree is merely planted and allowed to grow, it develops into the wild olive, a bush that grows without control into a tangle of limbs and branches producing only a small, worthless fruit (see Harold N. and Alma L. Moldenke, Plants of the Bible, p. 159). To become the productive “tame” olive tree, the main stem of the wild tree must be cut back completely and a branch from a tame olive tree grafted into the stem of the wild one. With careful pruning and cultivating the tree will begin to produce its first fruit in about seven years, but it will not become fully productive for nearly fifteen years. In other words, the olive tree cannot become productive by itself; it requires grafting by the husbandman to bring it into production. Throughout its history Israel has demonstrated the remarkable aptness characterized by the symbol of the olive tree. When they gave themselves to their God for pruning and grafting the Israelites prospered and bore much fruit, but when they turned from Christ, the Master of the vineyard, and sought to become their own source of life and sustenance they became wild and unfruitful.
Two other characteristics of the olive tree further illustrate how it is an appropriate symbol for Israel. First, though requiring nearly fifteen years to come into full production, an olive tree may produce fruit for centuries. Some trees now growing in the Holy Land have been producing fruit abundantly for at least four hundred years. The second amazing quality of the tree is that as it finally grows old and begins to die, the roots send up a number of new green shoots that, if grafted and pruned, will mature into full-grown olive trees. The root of the tree will also send up shoots after the tree is cut down. Thus, while the tree itself may produce fruit for centuries, the root of the tree may go on producing fruit and new trees for millennia. It is believed that some of the ancient olive trees located in Israel today have come from trees that were ancient during Christ’s mortal ministry. How can Israel be compared to an olive tree, which time and again seems to have been cut down and destroyed, yet, each time a new tree springs forth from the roots?
Zenos was not the only prophet to use the olive tree as a symbol for the chosen people of God. Jeremiah, foreseeing the coming destruction of the Jews by Babylonia, compared the covenant people to a green olive tree consumed by fire (see Jeremiah 11:16). The apostle Paul used a brief allegory almost identical to that of Zenos to warn the Roman Christians against pride as they compared their favored position to that of the Jews (see Romans 11:16–24). In modern revelation, the Lord uses the parable of a vineyard and olive trees to show his will concerning the redemption of Zion (see D&C 101:43–58). Student Religion Manual pgs 47-48.
An allegory uses symbolic representations to convey moral or spiritual ideas. These symbols provide far more significant meaning to the story than appears on the surface. Almost everything in an allegory represents something else. In Zenos’s allegory, for example, the vineyard, the trees, the branches, the master, and the servants all represent realities of greater significance. The value of the allegory lies in understanding what is represented.
“The parable of Zenos, recorded by Jacob in chapter five of his book, is one of the greatest parables ever recorded. This parable in and of itself stamps the Book of Mormon with convincing truth. No mortal man, without the inspiration of the Lord, could have written such a parable. It is a pity that too many of those who read the Book of Mormon pass over and slight the truths which it conveys in relation to the history, scattering, and final gathering of Israel. Such members of the Church unto whom attention has been called to the great significance of this parable have said they fail to comprehend it. It is simple and very clear to the minds of those who earnestly seek to know the truth” (Joseph Fielding Smith, Answers to Gospel Questions, 4:141).