Arlie A. Powell
Horticulturist-Fruits, Auburn University
Plums have been grown in Alabama and other areas of the Southeast for many years. The prune-type plum (Prunus domestica), although perhaps the most important in the United States among the 18 species found world wide, is grown very little in Alabama. The Japanese plum (Prunus salicina), the leading fresh market plum grown in the country is the primary type of fruit produced in the state. There are few to no producers across the Southeast that rely upon Japanese plums as their primary fruit crop because of inconsistent cropping. In Alabama, plums are primarily grown as a secondary crop by peach producers, especially in the central Alabama area and in portions of some more northern counties. Culturally, plums have similar requirements to peaches, including rootstocks, training/pruning, pest management, fertility, water requirements and harvesting.
There are a number of major obstacles that make plum production a risky endeavor. As already noted, early flowering, resulting in crop loss from freezes in late winter-early spring is perhaps the most serious problem. However, the high susceptibility of Japanese plums to the Prunus disease complex in the Southeast, particularly bacterial, creates major problems with tree longevity. In general, varieties of Japanese plum have the shortest tree longevity (often 4 to 10 years) of all tree fruits grown in the state. Bacterial canker (Pseudomonas syringae) and plum leaf scald are the two most serious diseases affecting plums. Plum leaf scald disease is a part of the phony peach complex associated with Xylella fastidiosa, a bacterium. Black knot (Apisporina morbosa), a fungal disease, can also reduce tree production and longevity.
Plums are commonly propagated onto the same rootstocks used for peaches and nectarines. Where plantings are made on old orchard sites, Guardian peach rootstock is preferred. Lovell and Halford peach have been and continue to be the most commonly used rootstocks for the Southeast. Nemaguard peach rootstock may continue to be used in south Alabama when plantings are made on virgin sites.
In the most recent 10-year study on plum varieties in Alabama, results have been disappointing in regard to consistent production. Because of the poor cropping record demonstrated in these studies and in orchards, plums remain a very marginal commercial crop in the Southeast. Even the best of varieties fell short of sufficient yields to make them consistently profitable in this most recent 10-year study.
Home gardeners may still wish to grow some Japanese dessert plums even though they realize significant cropping may occur only half the time or less. Therefore, varieties that are worthy of AU-Cherry (self-fertile), AU-Roadside, AU-Rosa, AU-Rubrum, Crimson, Homeside, Byrongold, Robusto (suitable only as green plum), Morris, Ruby Sweet, and Black Ruby. Ozark Premier, although trees are usually short lived, can provide a few seasons of excellent fruit. Homeside has a lot of Ozark Premier characteristics including good flavor.
Most Japanese varieties recommended are only partially self-fruitful. Therefore, two or more varieties should always be used in commercial or home plantings for cross pollination. Methley, one of the most popular of home fruit varieties, is self-fruitful and can be grown without the use of additional pollinators.
Workers at Auburn University and the USDA Fruit and Nut Investigations Lab at Byron, GA will continue to evaluate promising plum breeding lines developed through the Auburn breeding program. Hopefully, one or more of these lines will provide additional named varieties that may be grown successfully in the Southeast.
Russian myrobalan plums are now being investigated in parts of the eastern US including Alabama. One or more of these selections may eventually show promise. These plums have similar fresh dessert type quality of Japanese plums but are reportedly more cold resistant and crop more consistently.