What is the best climate for plum production?
Answer: In the United States, nearly all of the commercially grown plums for fresh eating are hybrids of the Japanese plum introduced by a Berkley nurseryman in the 1870s and subsequently hybridized by Luther Burbank in the late 1800s. Today, 95% or more of them are grown in California. Burbank made many complex crosses between Japanese and American plums and was the first to cross the plum and apricot. Though the fresh plums in grocery stores today are essentially “Japanese,” they might contain germplasm from many species, thanks to Burbank. Prune plums are European, as are most canned plums. Again, most commercial production of plums is centered in California, but European plums are more cold-hardy than Japanese plums and bloom later, so the European plum can be grown further north. In fact, plums are adapted to a wide range of climatic conditions; at least some cultivars can be grown in almost every state. Commercially, Japanese plums and prunes are grown where rainfall during the growing season is minimal and humidity low to prevent diseases; this is why most production is in California. Cold hardiness is excellent for European plums, similar to apple and pear, but Japanese plums are less cold-hardy (similar to peach). Plums have chilling requirements ranging from 550 to 800 hours for Japanese, up to 1,000 hours for European. (A greater chilling requirement means that the plant will be slower to break dormancy, hence, less likely to bloom too early while frost is still a danger.) Rainfall during the growing season can reduce production by accentuating diseases and causing fruit cracking. As with other Prunus species, deep, well-drained soils with pH 5.5 to 6.5 give best results. However, plum roots are the most tolerant of all the stone fruits with respect to heavy soils and waterlogging.You can learn much more in the ATTRA publication Plums, Apricots, and Their Crosses: Organic and Low-Spray Production. It focuses on organic and reduced-spray management options for disease and pest problems of plums, apricots, and their crosses (pluots, apriums, etc.). It also relates progress in broadening the practical climatic adaptability of the apricot. The publication also discusses adding these fruits as specialty crops for small-scale, diversified farms and identifies marketing opportunities.