Rootstocks for Plum Trees
Rootstocks for grafting plums are typically separated by size: dwarfing, semidwarfing or standard size trees. Dwarf trees grow 8 to 10 feet tall, semidwarf trees grow 12 to 15 feet high and standard trees grow from 18 to 25 feet high. Smaller trees are generally more efficient and productive. Rootstock cultivars used for plums vary widely in the quality of plums they produce and their ability to tolerate wet soil and resist disease. They will grow in U.S.Department of Agriculture plant hardiness zones 4 through 9.
In 1987, two researchers from the University of California and one from the U.S. Department of Agriculture collected more than 100 cultivars of the Prunus genus and tested them for their performance as rootstocks. They took into account the compatibility of scions, the size, quality and amount of the fruit yielded and the size of the tree. By 1994, they concluded that "Citation" plum (Prunus domestica “Citation”) was the superior rootstock for plums and ceased further evaluation of plum rootstocks. The "Citation," a semidwarf, grows 12 to 18 feet tall. It induces early bearing of sweet fruit, is tolerant of wet soil, resists the root knot nematode and is winter hardy but does not tolerate drought.
Horticulturalists at the University of Missouri report that cultivars of "Myrobalan" (Prunus cesasifera) is the most widely used plum rootstock in the United States. "Myrobalan" cultivars are widely compatible with all plums. Researchers at Michigan State University report that "Myrobalan 29-C" (P. cesasifera "Myrobalan 29-C"), a widely used cultivar larger than "Citation," is immune to the root knot nematode and tolerates wet soils, but it grows shallow roots the first few years, tends to lean and grows profuse suckers at its base. It is susceptible to oak root fungus and the brown line viral disease.
Cultivars of "Mariana" (P. cerasifera x P. munsoniana) are also commonly used plum rootstocks. Mariana cultivars are larger than dwarf trees but smaller than peach trees. MSU researchers say the widely planted "Mariana 2624" (P. cerasifera x P. munsonia "Mariana 2624") produces good crops of plums, but does not anchor well when it is young and tends to produce root suckers. It resists root knot nematodes, oak root rot and prune brown line but is susceptible to bacterial cankers.
Rootstocks of "St. Julien" (Prunus insititia "St Julien") are popular plum rootstocks in the United Kingdom and Europe. MSU reports that "St. Julien" is very productive and tolerates heavy, wet soil. "St. Julien" is compatible with all plums, grows to 10 feet high and will bear plums in three to four years.
- University of California: California Rootstock Breeding Program
- Michigan State University: Plum Research
- University of Missouri Extension: Fruit Production
- Center for Alternative Land Use, Bangor University: Growing Plums and Damsons
- Cornell University: Plum Rootstock Trials in Geneva: A Progress Report
- Oregon State University: Prune Rootstocks for Western Oregon