Jacob 5 offers a detailed description of practices regarding the cultivation of olive trees. Information about olive trees in the text agrees well with what is known of ancient olive cultivation in ways that seem far beyond what Joseph Smith could have known. While Romans 11:13-26 refers to grafting of olive trees and has some obvious parallels to the Book of Mormon, significant enough that a common ancient source can be considered (naturally, those who don't accept the Book of Mormon can argue plagiarism), Paul's passage offers scant information compared to the extensive and detailed information in Jacob 5. Excellent discussion of the chapter is available from Brant Gardner's Multidimensional Commentary for Jacob 5, which includes an analysis of the links to Romans 11 and reasons why Paul may have been referring to or influenced by another ancient source that might have common roots with the writing of Zenos.
There is so much that can be said about the impressive details of Jacob 5 that an entire book of scholarly analysis has been prepared: The Allegory of the Olive Tree, ed. Stephen D. Ricks and John W. Welch (Salt Lake City: FARMS and Deseret Book, 1994), 624 pages. A good place to start is Chapter 21, "Botanical Aspects of Olive Culture Relevant to Jacob 5" by Wilford M. Hess, Daniel J. Fairbanks, John W. Welch, and Jonathan K. Driggs, pp. 484-562, along with other chapters about ancient olive practices and symbolism. The details in Jacob 5 appear to be a masterful and accurate representation of ancient horticultural practices regarding olive trees, including the art of grafting branches from one tree to another, which is still common for those caring for olive trees.
Below is an excerpt from John Gee and Daniel C. Peterson, "Graft and Corruption: On Olives and Olive Culture in the Pre-Modern Mediterranean," in The Allegory of the Olive Tree, pp. 186-247, taken from pages 223-224:
[Jacob 5] purports to be the work of an ancient northern Israelite author, living between 900-700 B.C., about olive growing. [Footnote 275 discusses the details leading to this conclusion.] Almost every detail it supplies about olive culture can be confirmed in four classical authors whose authority on the subject can be traced back to Syro-Palestine. Zenos's parable fits into the pattern of ancient olive cultivation remarkably well. The placing of the villa above the vineyards [Columella, Rei Rusticae I, 5,7] means that, when the master gives instructions to his servants, they have to "go down" into the vineyard (Jacob 5:15, 29, 38). It was also customary for the master of the vineyard to have several servants (cf. Jacob 5:7,10-11,15-16, 20-21, 25-30, 33-35, 38, 41, 48-50, 57, 61-62,70-72,75). [Cato, De Agri Cultura 10; Varro, Rerum Rusticarum I, 18.] When only one servant is mentioned in Zenos's parable, the reference is most likely to the chief steward. Likewise, Zenos's mention of planting (Jacob 5:23-25, 52, 54), pruning (Jacob 5:11, 47, 76; 6:2), grafting (Jacob 5:8,9-10,17-18, 30, 34, 52, 54-57, 60, 63-65, 67-68), digging (Jacob 5:4, 27, 63-64), nourishing (Jacob 5:4,12, 27, 28,58,71; 6:2), and dunging (Jacob 5:47, 64, 76), as well as the fact that dunging occurs less frequently in the parable than the nourishing, all mark it as an authentic ancient work. The unexpected change of wild olive branches to tame ones (Jacob 5:17-18) would have seemed a divine portent to our ancient authorities. [Theophrastus, Historia Plantarum II, 3,1.]And here is an excerpt from "Botanical Aspects of Olive Culture Relevant to The Allegory of the Olive Tree" by Wilford M. Hess, Daniel J. Fairbanks, John W. Welch, and Jonathan K. Driggs in The Allegory of the Oliver Tree (pp. 552-554):
Even more striking, for Joseph Smith to have made up the parable from these classical authors, he would have had to read all four: Theophrastus is the only one to discuss the differences between wild and tame olives, the tendency for wild olives to predominate, and prophetic use of the olive tree as a sign. [Romans 11:16-24 does mention wild and tame and grafting, but nothing about the fruit or the purposes thereof. A casual reading of Paul leaves the impression that it is as easy to be one way as the other.] Varro and Columella are the only ones to acknowledge the Phoenician connections. Cato and Varro are the only ones who discuss the servants' roles. Cato and Columella alone note the placement of the villa above the groves; Varro is the only author to discuss the "main top" in association with the "young and tender branches" (cf. Jacob 5:6). Yet Joseph Smith probably did not have access to these works. And even if he had, he could not read Latin and Greek in 1829. Theophrastus's Historia Plantarum first published in English in 1916, [Theophrastus, Enquiry into Plants, trans. Arthur Hort (London: Heinemann, 1916)] and no part of his De Causis Plantarum was available in English until 1927 [Robert E. Dengler, ... Ph.D. Dissertation, University of Pennsylvania, 1927]. While English translations of Cato, Varro, and Columella were available to the British in 1803, 1800, and 1745 respectively [Thomas Owen, M. Porcius Cato concerning Agriculture (London: White, 1803), ...], it is hardly likely that they were widely circulated in rural New York and Pennsylvania. Joseph Smith could have known nothing about olives from personal experience, as they do not grow in Vermont and New York. Can it reasonably be supposed that Joseph simply guessed right on so many details? And even if he somehow managed to get the details from classical authors, how did he know to put it into the proper Hebrew narrative form? [The narrative of Zenos follows the Hebrew narrative pattern as laid down by Robert Alter, The Art of Biblical Narrative (New York: Basic Books, 1981).]
Even if Joseph Smith had somehow gathered the details of ancient olive culture from someone who knew it intimately, he would still have had no plot. [Zenos's plot is much more complicated than Paul's, and if Joseph Smith is adding to the plot, it must be explained how he got the extra details ... and made them fit in with ancient olive lore.]
Based on the botanical and horticultural information present in the archaeological and historical record, and reflected in Jacob 5, we can conclude that the ancients were superb horticulturists and had a profound understanding of vital biological and plant cultural principles. Most of the botanical and horticultural principles in Jacob 5 are sound and are very important for olive culture.For online verification of olive culture principles from non-LDS resources, consider "The Secrets of Olive Trees" from BienManger.com (also LeGourmetMarket.com), from which the following excerpts are taken. That page verifies several concepts in Jacob 5, such as the ability of olive trees to grow in rich and poor soils, the importance of grafting, the ability to regenerate or rejuvenate a decaying olive tree, and the practice of applying dung:
In addition, the one or two points, according to our interpretation, that represent unusual or anomalous circumstances are necessary enhancements to the message of the allegory.
In this single chapter of the Book of Mormon there are many detailed horticultural practices and procedures that were not likely known by an untrained person, and may not have been fully appreciated by professional botanists or horticulturalists at the time the Book of Mormon was translated.
Even today, outside of olive-growing areas, professional horticulturalists may not fully appreciate some of the unique aspects of olive culture. Given the extensive detail about olive culture present in Jacob 5, we must give Zenos much credit for a high degree of horticultural knowledge, which many take for granted.
Examples of what the ancients and Zenos evidently knew were how to prune, dig about, dung, and nourish; how to graft tame to wild and wild to tame, and how to graft tame back into tame; how to balance tops and roots by pruning, and the reasons for doing this; how to save the roots of trees whose branches had decayed, and how to transplant branches to preserve the desired traits of good plants; how to preserve and store fruit and how to distinguish between good and bad fruit; how well plants grow on good and bad soil; how to care for trees to cause young and tender branches to shoot forth; that they could graft wild to tame to rejuvenate tame; that specific cultivars produced well in certain areas; . . . that they could burn an orchard to reestablish a new one; that plants grown from seeds would not have desirable characteristics; the importance of elimination of old wood and debris by burning, and how to deal with pests and pathogens; how to prevent heavy bearing one year and no bearing the next by proper pruning; the necessity to plant more than one cultivar for pollination; and how to propagate scions with the desirable genetic material.
Interestingly, much of this sophisticated technology was probably lost in the Nephite civilization, for the olive is not mentioned again in the Book of Mormon after Jacob 5, an indication that the lands of the Book of Mormon may not have been suitable for growing olives ... The only regions on the American continents with Mediterranean climates where olive culture is economically feasible are the regions of California, Chile, and Argentina.
Joseph Smith probably knew how to prune, dig about, dung, and nourish local fruit trees; he probably knew a little about grafting, and he may have been familiar with some other horticultural principles, but not likely those peculiarly related to olive culture.
SOILSHere is some information from a modern olive-tree cultivator:
The olive tree often grows on poor and dry soils, but gives remarkable results on rich soils (California) or by irrigation (Spain and Oranie). . . .
GRAFTING : the propagation of a given variety of table olives is done by grafting, except in special cases (cuttings, stump chips of the same variety).
Depending on what has to be grafted, the following techniques are being used :
For the seedlings and the sprouts coming from stocks of a different variety, you can use cleft grafting or budding.
In the case of older trees, be it the grafting of wild olive trees or of olive groves whose production is to be modified, it is advised to use inarching or bark grafting. . . .
It may be necessary to rejuvenate an olive grove if it has not been maintained for a long period or if it has suffered accidents, thus becoming unable to produce a normal crop.
It is sufficient to cut away all branches, except the largest ones and then graft the remaining stumps. The grove should then bear a unique variety of table olives and be able of bearing fruit in excellent conditions.
A trunk in very bad shape should be cut at the base in order to start with three replacing shoots. . . .
Although manuring largely pays off, olive trees are still too rarely manured. Manure should be organic, on a basis of dung or cattle cake.
When possible, a culture of green fertilizers (vetch, lupin, etc.), mowed at maturity and ploughed in, will complete the dressing of organic matter. . . .
Some ancient olive trees in Jerusalem at the Mount of Olives date back 2000 years. When old large limbs are pruned on large aged olive trees, new branches grow and a new olive crop grows. . . .Other olive-related resources are provided by the University of Georgia (note the discussion of soils, indicating that olive trees can grow on soil too poor for ordinary cultivation, consistent with Jacob 5) and the California Rare Fruit Growers.
The leaves of olive trees are gray-green and are replaced at 2-3 year intervals during the spring after new growth appears. Pruning yearly and severely is very important to insure continued production. The trees have the unproductive limbs removed, "so that it will be more fruitful" John 15:2. An olive tree can grow to 50 feet with a limb spread of 30 feet, but most growers will keep the tree pruned to 20 feet to assure maximum production. New sprouts and trees will emerge from the olive tree stump roots, even if the trees are cut down. Some olive trees are believed to be over a thousand years old, and most will live to the ripe old age of 500 years.
Olives generally are beaten off trees with poles, harvested mechanically or by shaking the fruit from the trees onto canvas. Most ripening olives are removed from the trees after the majority of the fruit begins to change in color. It is important to squeeze out the olive oil within a day after harvesting or else fermentation or decline in flavor and quality will occur. The olive oil can be consumed or used in cooking immediately after its collection from the press. Olive oils are unique and distinct, each brand of olive oil having its own character, as determined by many factors, like those unique flavor differences found in fine wines. Prepared commercial olive oils can vary greatly in aroma, fruit flavor; whether the taste is, flowery, nutty, delicate, or mild, and the coloring of olive oil is quite variable. . . .
Olive trees can survive droughts and strong winds, and they grow well on well drained soils up to a pH of 8.5 and the trees can tolerate salt water conditions. In Europe, olive trees are normally fertilized every other year with an organic fertilizer. Alternate bearing can be avoided by heavy pruning and generally the trees respond to this very quickly and favorably.
Olive trees should be purchased that have been vegetatively propagated or grafted, because the seed grown trees will revert to a wild type that yields small olives with an insipid taste. Olive trees are more resistant to diseases and insects than any other fruit tree and, therefore, are sprayed less than any other crop.
The Book of Mormon does not say that the Nephites raised olives, however. For more information on the issue of plants and animals in the Book of Mormon, you might want to see my LDS FAQ page on that topic.