History of plum trees and their hybrids

Documentation of ancient plums growing in ancient times is sparse. The best evidence for that older existence is best documented through America’s most famous pomologist, Luther Burbank, who reported in his twelve-volume botanical literary classic, Small Fruits, Volume IV, page 136, that the European plum, Prunus domestica, and its fruit ancestor originated in the Caucasus Mountains near the Caspian Sea. Burbank detailed evidence that the prune (dried plum) was a staple food of the Tatars, Mongols, Turks, and Huns “who maintained a crude horticulture from a very early period.” Various websites have advanced the absurd idea that because the European plum, Prunus domestica, no seeds were found in the ruins of Pompeii after the eruption of Mount Vesuvius in AD 79, “while most other old world fruits were”, that this Plum could be concluded to be a recent hybrid of “spontaneous chromosome” doubling to produce hexaploid offspring.

The earliest reference to the history of plums in the American colonies comes from the Prince Nursery of Flushing, New York, which was established in 1737 and reported in 1771 in an advertisement for “33 kinds of plums” for sale. These plums were undoubtedly European plums, Prunus domestica.

After the year 1755, Henry Laurens, a guest and friend of Wililam Bartram, introduced olives, limes, ginger, perennial strawberry, red raspberry, and blue grapes to the United States. From the south of France he introduced apples, pears, plums, and the white Chasselas grape, which bore abundant fruit. Henry Laurens lived in Charleston, South Carolina and served as president of the Continental Congress.

William Bartram described two species of American plums in his famous book, Travels, on his 1792 trip to Georgia, where he identified the Chicasaw plum, Prunus chicasaw, and in Alabama he found a wild plum, Prunus indica.

Luther Burbank did more to improve and hybridize plum trees of different species than any other person in history. His work on the plum group of stone fruits is distinguished from any other by his unparalleled contribution to the improvement of various fruits grown and enjoyed today.

Burbank claims that his importation of twelve plum seedlings in the year 1885 was the “most important importation of fruit trees ever made at a single time into the United States.”

Burbank brought plums from all over the world and crisscrossed them in a giant “melting pot” to produce the best characteristics and reject the wrong ones. These genetic mixtures of plums were recombined over many generations, resulting in hybrid plums that are so different from the original species that they appear to be new species.

Burbank claimed it spent more time hybridizing plums than with any other breeding program, reporting that it evaluated 7.5 million hybrid plum seedling crosses before releasing prominent cultivars for sale. His famous line of plums, which were popular in the late 1890s, are still admired and grown commercially for sale and in backyards today, including Burbank, Santa Rosa, Wickson, Golden, Satsuma, Shiro, and Ozark. premier. The first big hit of his was applauded by USDA Professor HE Van Deman who suggested that Luther Burbank’s creation be named after its creator, hence “Burbank Plum.”

The most successful crosses between plums come from the more exotic Japanese plum, ‘Satsuma’, a name suggested by USDA Professor HE Van Deman, who identified it as imported from the Satsuma province of Japan. This unique plum developed a red skin with an overlay of pale blue mesh blossoms. The flesh was dark purple-red in color, firm, tasty and of excellent quality to be preferred for home use.

Burbank’s experimental species were Japanese plums, Prunus triflora, which grew wild in Japan and were picked by the natives. Japanese plums grew in many colors on the skin from white to purple, they were large and rather tasteless, but the Japanese natives ate them while they were green and hard. Japanese plum genes appear to dominate most hybrid plum offspring. Chinese plums, Prunus simonii, were aromatic, with richly colored skins, a small pit, but the skin cracks, and the fruit tastes bitter.

European plums, Prunus domestica, vary in size from largest to smallest, sweet or tart, complex genes, many colored skins, highly adaptable, good to eat fresh, dried or canned. The downside: They are too juicy or watery. “Green Gage” is a well known standard European cultivar. Prunes are very high in sugar content.

Several species of American plums are very hardy and productive to the point of covering the ground in spring with several layers of fruit. These plums may be tasty but have poor shipping quality. Burbank released an excellent hybrid strain of this cross called “Robinson plum”.

Luther Burbank has used several species of Native American plums in hybridization experiments. American plums, Prunus americana, wild goose plums, Prunus hortulans, chicasaw plum, Prunus augustifolia, western sand plum, Prunus besseyi, beach plum, Prunus maritima, and California wild plum, Prunus subcordata. These native plum trees are unusually cold hardy and are not harmed by cold temperatures, even in the northernmost part of the central United States.

The “Myrobalan” plum originated as a French species, Prunus cerasifera is widely used as a peach and plum rootstock that tends to be compatible with the resulting fruit tree union and appears to be highly resistant to nematodes and root diseases.

Burbank’s goal in hybridizing plums was to produce a tree that had “stability, novelty, variety, hardiness, beauty, shipping quality, and adaptability.”

Plum leaves and twigs exhibit many subtle characteristics that the plant breeder can experiment with to predict future characteristics of fruit to be grown from small seedling crosses. Most known hybridizers from experience have a predictable result, although these plant qualities are too intangible to explain to an audience, such as changes in facial expressions or small variations in color changes. If the leaves of a plant are dark red, the fruit will be red. This same phenomenon is applicable to flowers such as canna lily leaf color and rhizome color red; or in crinum lily cultivars, a red bulb means a red flower; a light green bulb means a white flower.

Luther Burbank developed a seedless plum by hybridizing a French plum variety, “Sans noyaii.” These plums develop various skin colors ranging from white to yellow, scarlet orange, crimson, violet, deep blue, almost black, striped, spotted, and mottled. These seedless plums were delicious and unique, but were never commercially successful with growers or in public demand.

Burbank crossed many plums that had a tendency to produce fruit with a high sugar content, such as sweet figs, pineapple, and oranges. This high sugar content makes it possible for the plum (prune) to ensure long-term preservation, when dried. The plum contains a thick, hard skin of such a texture that it is required not to crack when the commercial drying process begins and proceeds to deliver a flavorful, honey-sweet fruit that lasts well.

A plum will not dry properly and become a marketable fruit unless the plum contains a sugar concentration of at least 15%. Before drying, the prune is briefly immersed in an alkaline solution that prevents future fermentation by stopping microbes from growing on the surface of the skin. For satisfactory prune production commercially, a prune tree must be a reliable producer with a substantial annual crop of fruit. Prunes must ripen early, when the days are long and warm, and must fall from the tree to avoid high harvest costs at the proper time of ripening. The prune should be cured and dried to a black color and develop a small pit. Most plum hybrids have been hybridized from the European plum, Prunus domestica.

There are also three ornamental varieties of flowering plums that are recommended for planting: Newport, Prunus cerasifera ‘Newport’, Purple Pony Prunus cerasifera ‘Purple Pony’, and Red Leaf Plum Prunus cerasifera ‘Thundercloud’, flowering plums.

Burbank developed purple left plums from an ancestor of the purple-leaved French plum, Prunus pissardi, which are commercially sold as ‘Thundercloud’, Vesuvius and Othello flowering plums. Some of these red-leaved flowering plums developed by Burbank produced luscious red fruit in addition to the beautiful red ornamental leaves.

Plum is high in antioxidants that offers many health benefits such as vitamin A, vitamin B1, vitamin B2, vitamin C, niacin, and minerals; Calcium, Potassium, Phosphorus and Iron.

Burbank evaluated the intricacies of hybridizing the plum and even crossed the plum with the almond, Prunus dulcis, in hopes of creating a tasty almond seed and flavorful pulp. He created many crosses with the apricot, Prunus armeniaca L., and created plums, a 50/50 mix of plums and apricots; The pluot trees demonstrate a 75/25 mix of plum and apricot; and Aprium trees, a 75/25 mix of apricot and plum.

Copyright (c) 2006 Patrick Malcolm