Two of our four plum varieties have blossomed by early March 2015. On our 4-N-1 grafted plum tree, the Santa Rosa variety started mid-February with its thinly spaced blossoms. This week the Burbank variety bloomed with dense sets of flowers.
Burbank plum trees were developed by noted plant breeder Luther Burbank in 1883.
Prized for its heavy crops of reddish-purple fruit, dwarf Burbank plum (Prunus salicina “Burbank”) offers a good choice for home orchards. Its compact growth of 8 to 10 feet at maturity makes it easy to maintain, prune and harvest. Hardy in U.S. Department of Agriculture plant hardiness zones 5 through 9, Burbank plum requires about 400 chill hours per year. A Japanese variety of plum, Burbank requires pollination by another Japanese type plum, such as “Santa Rosa” (Prunus salicina “Santa Rosa”).
Pruning at Planting Time
Plums are usually planted during the dormant season in late winter or early spring, before growth begins for the year. Dwarf Burbank plum trees, like all Japanese plum trees, are best pruned to an open center shape without a central leader. You can begin pruning to this shape at planting time. If you’re planting a one-year-old “whip” tree with no branches, prune it back to about 3 feet in height at planting time. If you’re planting an older tree that has branches, remove all but four evenly spaced branches around the trunk and cut their length back by one-third at planting time.
First Year Pruning
After the first year of growth, dwarf Burbank plums should be pruned in late winter or early spring, when the tree is dormant. Remove branches that are crossed or are closely spaced on the trunk. Burbank plums, even dwarf varieties, tend to bear heavily and require a good framework of solid scaffold branches. Remove branches that form a “V” shape with the trunk – these will invite splitting and will not bear the weight of fruit well. Leave evenly spaced branches that form a 45-degree angle with the trunk.
Subsequent Year Pruning
Continue pruning each year before growth begins in the spring, removing about one-third of the new growth. Prune out water shoots, crossed branches and any large branches that limit airflow through the center of the tree. If the fruit spurs have grown too long and droop or bend down, prune these back to allow them to bear the weight of the fruit.
Pruning After Fruit Drop
Each year as the fruits form on the dwarf Burbank tree, some of the developing plums will begin to fall to the ground in early summer. This “fruit drop” is a mechanism the tree uses to thin excess fruit. Once the fruit drop has subsided, clean up fallen debris and use pruning shears to thin the remaining plums to 3 to 4 inches apart on the spurs. For even larger plums, thin to 6 inches apart.
Pruning at Other Times
Although you will typically prune the dwarf Burbank plum tree only once in late winter, and prune again to thin fruit in early summer, it may be necessary to prune at other times of the year. Remove damaged branches at any time of the year, as well as water shoots, diseased wood and sprouts that form below the graft on the trunk. As in all pruning, use sharp hand-pruning shears for small branches and a pruning saw for branches larger than 1 inch in diameter. Keep these tools sharp for clean cuts, and if pruning diseased wood, disinfect the tools with isopropyl alcohol between cuts.