Answer: The following page includes a diagram on how to train a plum tree into an open center; note that plums are not pruned during the winter. Instead, they are pruned in spring. http://www.ces.uga.edu/pubcd/c743-w.html
Some suitable matches for your Santa Rosa plum include Beauty, Fortune, Hollywood, Santa Rosa, Methley, Cocheco, Shiro, Sprite, and Delight; your fruit tree source may also have some suggestions.
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