American plum is native to North America from Saskatchewan to New Mexico east to New Hampshire to Florida. It spans six hardiness zones (3 through 8) and grows in most soils with a pH level between 5.5-7.5. It is moderately tolerant of drought. Native Americans used the fruit extensively and used the roots to make a red dye. It is used as an ornamental tree and for windbreaks. The fruit is eaten fresh and is processed as preserves, jellies and wine. It is used in plum breeding to contribute winter hardiness to hybrid offspring. American plum rootstock is grafted on plum cultivars and planted as specimen trees as a pollinizer for Japanese plum and plum hybrids that require cross-pollination.
Observations at Carandale Farm
American plum in bloom
Four American plum seedlings were purchased in 2004 as a pollinizer species. All grafted plums ordered from St. Lawrence Nurseries are grafted on P. americana rootstock for hardiness. When the scion (above ground portion of the tree) dies, new top growth emerges from the rootstock, forming a new tree with all the genetic traits of the rootstock: In other words, another American plum. With these volunteers, there is now a total of 11 American plum at the test plot. Since these are all seedling trees, no two are the same. All the fruit is some shade of red when fully ripe, and most have strong abscission and drop on the ground when ripe. As the photo shows, size and shape vary significantly.
Fruit quality is also highly variable. They all have sweet flesh and pits that cling to the flesh (clingstone). Skins tend to be tart and thick, but this varies. Even fruit with tart and/or thick skins make excellent jams, jellies, and sauces (and probably wine). There are some with thinner and/or sweeter skins that have good dessert quality.
Fruitfulness is variable, but some trees produce abundantly and consistently. Most had good fruit set in 2012 despite adverse weather. They are well received by customers who ask for them at the Dane County Farmers’ Market. Even out of this small sampling, there are some with niche economic potential as a specialty crop in a local/regional marketing scenario. Their tendency to drop on the ground when ripe is inconvenient and could pose health concerns, but it could also be turned into as asset, using tarps to harvest.
American plum is a well-adapted, native fruit useful as a pollinizer plant, in breeding programs for its winter hardiness and as a rootstock for other plums. Also, specific clones could have merit as an economically sustainable fruit crop in an integrated production system. American plum does need to be managed for root suckering. This is another native species, like the native blackberry, that is naturally adapted and has developed tolerance to native pests through natural selection. They are both very fruitful in a managed environment.
Wikipedia entry on American Plum
North Dakota Tree Handbook entry on American Plum
University of Florida IFAS Extension Fact Sheet on American Plum
NDSU Carrington Research and Extension Center, click on Northern Hardy Fruit Evaluation Project, then Fruit Index-Plum